25074312.pdf - International Nuclear Information System (INIS)

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original containscolor illustrations

TRNDestination

InstitutMax von Laue-Paul Langevin

Grenoble - France

The ri'nuiiitea reactor building

Jean C/ii/ivn/i/i. Dirt-dor.On llic (/«y nfilie arrival oftlic new !)->()reflector tank ( \efit in llic hiick^

Front coverThe new D-jO retlector tank hein» lowered into the empty reactor swimming pool on 2 March 1944.

- CONTENTS -

- ORGANISATION OF THE ILL p. 5

- VISITS AND EVENTS p. 8

- DIRECTOR'S REPORT p. 14

- ILL-ESRF-EMBL-CoopERATiON p. 20

- COLLEGES : p. 21

COLL 2 - THEORY P. 22

COLL. 3 - NUCLEAR AND FUNDAMENTAL PHYSICS P. 28

COLL. 4 - STRUCTURAL AND MAGNETIC EXCITATIONS P. 38

COLL. 5 - CRYSTAL AND MAGNETIC STRUCTURES P. 46

COLL. 6 - LIQUIDS, DISORDERED MATERIALS

AND METAL PHYSICS P. 63

COLL. 8 - BIOLOGICAL STRUCTURES AND DYNAMICS P. 82

CoLL.9a - MOLECULAR SPECTROSCOPY, SURFACESAND MESOPHASES P. 86

CoLL.9b - LARGE MOLECULES P. 96

- DIRECTORATE SERVICES : p. 101

- SCIENCE DIVISION IDS): P. 103SCIENTIFIC SUPPORT P. 104

NUCLEAR AND FUNDAMENTAL PHYSICS (NFP) GROUP P. 106

DIFFRACTION (DIFFj GROUP P.I 10LARGE SCALE STRUCTURES (LSS) GROUP P.I 15

THREE-AXIS SPECTROMETER (TASj GROUP P.I 18TlME-OF-FLIGHT AND HlGH RESOLUTION (TOF/HR) GROUP P. 120

SMALL PROJECTS IN DS P. 123

- CONTENTS -

- PROJECTS AND TECHNIQUES DIVISION (DPT) : P. 127INSTRUMENTATION BRANCH P.I 30

DEVELOPMENT BRANCH P. 135

- INSTRUMENTS - PROJECTS - TECHNIQUES p. 140

- REACTOR DIVISION : p. 145DISMANTLING P. 145

RECONSTRUCTION P. 148

STUDIES AND METROLOGY p. 152

BUDGET AND TIMETABLE P. 152

- ADMINISTRATION DIVISION : p. 153FINANCE AND MANAGEMENT INFORMATION SYSTEMS P. 154PURCHASING P. 156PERSONNEL AND HUMAN RESOURCES P. 157

BUILDING AND SITE MAINTENANCE P. 159

- COMMUNICATIONS : p. 161SEMINARS P. 161

WORKSHOPS p. 166

THESES p. 167

CONFERENCE CONTRIBUTIONS P. 168

PUBLICATIONS - ILL-REPORTS P. 174

AUTHOR INDEX p. 194

PAPERS ACCEPTED FOR PUBLICATION P. 202

EXTERNAL ORGANIZATION OF THE ILL

Associates of the ILL

FRANCE UNITED KINGDOM FEDERAL REPUBLICOFGERMANY

( iwimiss.irul ScioiKV .nul l-.niMiiociui!:j ri'norsii' -Miumquo iC'l \i Rosraioli Cuiiiu'il iSl-KO Koiiilnivoliuii'Vonlriini

Kiiilsiuk'lKI-KlС onlro A.iiinn.il

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AUSTRIA

Osioiiok'lii4-|ioAk,nlonno

Countries with scientific membership

)llcnnics(KI-'K)

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)SL-hniK-k(BMFT)

)Slcincr (HMI. Bi:rlin)

Steering Committee(ut its last meeting)

) Aymar (С'КЛ)

) Boiichiiril (С1-Л)

)Comès(CNRS)

)Sevin(C'NRS)

) Richards (Univ. Durham))Taylor(RAL))Ward(SKRC))Wilkins(SKRC)

Plenary Session

3(1 parlicipanK

Scientific Council

Subcommittees

66 members

NEW ORGANIGRAM

DIRECTOR'S SERVICES

SAFETY, MEDICAL,HEALTH PHYSICS SAFETY ENGINEER EXTERNAL RELATIONS

& ENVIRONMENT H. Schweitzer B. Corner, J. F. VeyralJ.F.Veyrat .

A»»inOfit Dimdw .

COLLEGE SECTOR

. 2 ТНесйу

3 Fundamental & Nuclear

Physics ,

4 Structural & Magnetic

Excitations

5 Crystal & Magnetic

. Structures

6 Liquids, Disordered

Materials • ,.

8 Biology

9 Chemistry ( i

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N [. w ORGANIGRAM

DIRECTORJ. Charvolin

PROJECTS & TECHNIQUES :'DIVISION ,!

P. Schofield ,:

Assistant Director !

INSTRUMENTATIONBRANCH

A. Heidemann

1 1 _ ~ " ' Л ~

NEUTRON DISTRIBUTION& CENTRAL SERVICES

r - MECHANICS

r- ELECTRONICS

COMPUTING:INSTRUMENTS, NETWORK

INFRASTRUCTURE

COMPUTING:SYSTEMS,

COMMUNICATIONS

DEVELOPMENTBRANCH

C.M.E. Zeyen

.— MONOCHROMATORS

DETECTORS

MULTILAYERS/BEAM OPTICS

r - CRYOGENICS

HIGH TEMPERATURESHIGH PRESSURES

INSTRUMENTALTECHNIQUES

REACTORDIVISIONE. Bauer

SHIFT TEAMS,SITE SECURITY

ELECTRICITY& ELECTRONICS

MECHANICALSERVICE

ADMINISTRATIONDIVISION

H.M. Spilker

iwauK мжикшнм

PERSONNEL,0

& HUMAN RESSOURCES

FINANCE& MANAGEMENT

INFORMATIONSYSTEMS

, - PURCHASING

BUILDING& MAINTENANCE

"Visirs AND EVENTS" IN 1993

" Wiilti'i' Mainpe Memorial Colloquium " iiiytini~etl />v M. I'eiutlehiin on 2(J Juniuiiy.

"Walter Manipe Memorial Collm/iiium "I-'rom left l<> right : IMIC W. l'uni../. Ки/плwul J.-li. Suck.

" Waller Mampe Memorial Cnl/ot/iiitnn ".

M. Prntllehury. N. Runr.cy.

ami Kiithi M(ini/>e. Waller's wife.

" V / .s / / .s л N p E v I N i > " ; N '1993

Joint II.I.-I'SRI-' Colliii/iiitiin l>\ (leorxe.Yo/V/ /'/•/,-(• и'НИН'Г, llelll Oil . ' / MtlIYll.

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"VISITS AND E V [ N I S " IN 1993

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" V i s : т s AND EVENTS" IN 1993

O. S<'litiri>l'i>ri'\t'iil\ llif iiiMrwiifiil 1)7Itt (î. Sïttltcnhct'it. ./. Chtn'rolin. \'. Knii11. Damer, nut/ A. Hcii/t'ini/ini li.Mcii.

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"Visirs AND EVENTS" IN 1993

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П. Riflilt-r i.liili< /n on .2-24 Мчгс/i ill itir ILL.

Workshop "Dyiitiniii-i oj /)/w>r</<'m/

Mtiu-m<l\ II" l-'i'im: Icjt in rift/it :

Л/n. M. ami Mr. U. Dnhlhorff. Л. UV/.i;/». :'v

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"VISITS AND EVENTS" IN 1993

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REUNION ANNUELLEUGROUPE FRDNGM

D'ETUDE DESQUASICRISTAU

RAPPORT ou DIRECTEUR

S i 1992 avail été l'année marquée parl'expression de la volonté dc.s Associés del'ILL de maintenir TILL Mans son statut de

laboratoire multinational. 1993 a été celle pendantlaquelle cette volonté a été nunénalisée par lasignature à Paris, le 25 mars, de ! Avenantprolongeant la Convention Intergouvemementaleentre la France. l 'Allemagne et la GrandeBretagne, pour au moins dix ans à partir du1er janvier 1994. Ceci a permis d'entreprendre lesnégociations avec les Membres Scientifiquesactuels et potentiels en vue de l'établissement decontrats valables à partir de ce lei- janvier 1494.Nous préparons actuellement les signatures desnouveaux contrats avec l'Autriche. l'Espagne et laSuisse. C'est évidemment avec une très grandesatisfaction que l'ILL voit se reconstituer le cadrejuridique liant entre eux les pays, donc lescommunautés, participant à son exploitation et àsa vie scientifique. C'est aussi un élément demotivation puissant pour la poursuite des actionsen vue du redémarrage, qui concernent la remiseen étal du réacteur, la réinstallation desinstruments et la mise en place de la nouvellestructure de l'Institut.

Depuis le démontage de l'ancien bidonréflecteur à la fin novembre 1992 l'accent a étémis sur la préparation du remontage. La piscine aété totalement nettoyée, la résistance mécaniquede son revêtement contrôlée et sa géométrievérifiée. L'étal de propreté atteint est remarquable,puisque les équipes peuvent y travailler sansprotection particulière, et les contrôles etvérifications nous montrent une piscine dans unétat très proche de celui d'or igine. Aucuneintervention supplémentaire sur la piscine n'a éténécessaire. Elle est maintenant prêle à recevoir lenouveau bidon dont la fabrication avance commeprévu et qui devrait arriver début février 1994.Pour terminer avec les aspects techniques jementionnerai que l'avance de la découpe del'ancien bidon nous a permis d'examinerdirectement la grille avec les fissures qui son! àl'origine de la remise en étal et de confirmer lemécanisme proposé par l 'ILL pour l'apparition deces dernières. L'ensemble de ces travaux a éléconduit du mieux possible grâce au dynamisme età la compétence des équipes de l'ILL. ainsi qu'àl'esprit de honne collaboration manifesté par lotisles participants à ce projet. La procédureadministrative nécessaire pour l'obtention dudécret d'autorisation de redémarrage se déroule

tout à lait normalement, l 'ILL a l'ail parvenir lesdossiers nécessaires aux autorités compétentes auxdates prévues, ils ont élé examinés par cesautorités qui mettent en place les dernières actionsde la procédure. Le déroulement de l'ensemble desactions, aussi bien techniques qu'administratives,ainsi que l'évolution des dépenses, sont analyséstrès régulièrement par le sous-comité "Remise enétat" qui a conclu, lors de sa dernière visite à l 'ILLle 18/10/1993, que les coûts et délais sontactuellement respectés et qu'aucune indicationn'apparaît qui conduirait à penser que la dateprévue de redémarrage ne puisse être respectée.

Ayant maintenant la quasi cerlitiide que leréacteur redémarrera mi-1994 il importait delancer le programme de réinslallation desinstruments pour que ceux-ci soient disponibles aumême moment. Nous commençons par les travauxdans les halls des guides et nous poursuivrons parle remontage des instruments du niveau C. quiavaient élé entièrement démontés pour libérerl'accès au réacteur, dès que les doigts de gantseront réinstallés. Pour cela l ' Insti tut doitreconstituer au mieux le potentiel humainnécessaire en rappelant ses scientifiques ettechniciens travaillant dans d'autres centres etlaboratoires. Nous n'éviterons cependant pas unesituation difficile car l'Institut mène maintenantdeux importants projets techniques de front,réacteur et instruments, et certaines compétences,que nous r.e pouvons pas doubler en raison deslimitations d'effectifs, sont nécessaires sur cesdeux projets.

Une d e r n i è r e a c t i o n nécessa i re aufonctionnement futur de l'Institut a été la mise enplace de la nouvelle structure en quatre Divisions.Celle action est l'aboutissement d'une longuepériode de discussions et de réflexions initiées parl'analyse de l'organisation et du fonctionnementde rinsiitui effectuée par un Groupe d'études à lademande du Comité de Direction le 27/11/90.Le projet définitif de réorganisation avait éléaccepté par le Comité de Direction réuni le02/06/93 à Ahingdon et nous avons tenu à lemettre en place le plus tôt possible afin que ladélicate période du redémarrage ne soit pasperturbée par un tel bouleversement et querinslilul soit prêt à fonctionner dans ce nouveaucadre dès le redémarrage de l'installation prévupour la mi-1994. Le changement de structure adonc eu lieu le 01/07/93. très vite après la dernière

R Л Г Р О К ! PU D ! К I С ! Г (/ f?

réunion du Comité do Direction. Si l'Instituttravaille depuis cette date dans su nouvellesiructure. l'elTectit' correspondant à celte dernièren'est pas encore atteint ainsi que la distributionfinale du personnel dans les nouvelles unités.L'effectif est en effet en pleine évolution suite auxpremiers départs dans le cadre de la ConventionFNE. aux retours des scientifiques et techniciensqui avaient rejoint d'autres centres ou laboratoirespendant l'arrêt et. enfin, aux recrutementsnécessaires, en particulier dans le secteurscientifique. Ce n'est que dans le courant 1УУ5que nous atteindrons l'effectif de l'ordre de 400envisagé dans la nouvelle structure. Réorganiserun institut dans le cadre d'un effectif limitéimplique aussi des mutations internes qui nepeuvent pas être toutes réalisées dès maintenant enraison des priorités actuelles qui ne sont pas cellesd'un institut en fonctionnement normal. Lesdéparts et mutations qui accompagnent une telleréorganisation dans une entreprise bouleversentprofondément, et parfois péniblement, le réseau derelations qui ont lié ses membres et nous devonssouligner que. dans notre cas. celte réorganisationse fait avec la participation constructive dupersonnel qui sait dominer les doutes et anxiétésque génère une telle situation.

Nous venons d 'examiner t ro is points-réorganisation, remise en état du réacteur,réinstallation des instruments- nécessaires pourpermettre à l'ensemble de l ' instal lat ion deredémarrer à la т!-1УУ4. puis de fonctionnercomme souhaité avec 5 cycles et 25 instruments.Nous envisageons 2 cycles en 1УУ4. le premierétant consacré à la mise au point finale desinstruments et le second étant ouvert auxutilisateurs. Les propositions d'expériences serontexaminées par les sous-comités du ConseilS с i e n t i f i q u e e n a u t о m n e 1 У У 4 et n о u sdistribuerons le temps de faisceau pour un premierensemble de 3 cycles. ! en 1УУ4 et 2 en 1УУ5. Lesconditions de ce redémarrage doivent être assuréespar un budget comprenant les contributions desAssociés, comme prévu dans l'Avenant à laConvention Intergouvemementale et le Protocoled'Accord, signés le 25.3.1УУЗ. et par celles desMembres Scientifiques. Ces conditions sont asse/contraignantes et. pour l'instant. l'Institut doitconsacrer ses efforts au retour à l 'activitéexpérimentale, la reprise de l 'activité dedéveloppement devant être plus lente. Dans cesnouvelles conditions nous n'offr irons que

25 instruments programmés aux utilisateurs, cenombre est inférieur à celui d'avant l'arrêt, nousrecherchons actuellement une formule quipermette de réintroduire partiellement lesinstruments déprogrammés dans le programme ennégociant les conditions de leur exploitation avecdes groupes extérieurs pouvant finaivjer celleopération dans le cadre de "CollaboratingResearch Group" (CRG). Enfin, ni) signe trèspositif est que l'Institut commence à reconstituerl'effectif de son secteur scientifique qui avaitbeaucoup décru ces dernières années. Huit jeunesscientifiques ром-doctoraux seront embauchésdans le début de 1УУ4. les recrutementscontinueront jusqu'à la fin de 1УУ5 pour atteindrele nombre total de 22 sur ces deux années,les premiers boursiers de thèse seront accueillisîles octobre 1УУ4.

Nn'js concilierons ce rapport en disant que nousconsidérons que tout est mis en oeuvre pour quel'Institut reprenne ses activités scientifiques et deservice en 1УУ4 et ceci quelle que soit laconjoncture générale. L'Institut tient à réaffirmerainsi sa vitalité et ses engagements envers lescommunautés scientifiques qui le soutiennent.Si les budgets 1УУ4 et 1УУ5 nous permettentd'assurer ce retour en exploitat ion, ils nepermettront pas encore le lancement de nouveauxdéveloppements importants. Nous souhaitons uneamélioration rapide de la situation budgétaire afinque l'Institut puisse reprendre le plus rapidementpossible son rôle tie création et de développementen instrumentation neulronique : et ceci n'était pasle moindre des services que l'Institut rendaità la communauté internationale.

.1. Rossat-Mignod. membre du ConseilScientifique, est décédé brutalement à la fin dumois d'Août. Il fut responsable du "Service deMagnétisme et Diffusion Neutronique" au CENGavant de devenir Directeur du Laboratoire LéonBrillouin à Saclav. Il était bien connu et trèsapprécié par la communauté internationaleneulronique pour sa très haute compétence.A l ' ILL. où il comptait de nombreux amis etcollaborateurs, sa mort a été ressentie commela perte d'un de ses membres.

Jean Charvolin

D / R l- С 1 С О R Т

W h i l e 1492 was characteri/ed by theexpression of the I'LL Associates' will tomaintain the InsiiUit's status as a

multinational laboratory, 1993 was the year inwhich this was confirmed by the signature in Parison 25 March of the Protocol expending theIntergovernmental Convention between France.Germany and the United Kingdom for at least tenyears from 1 January 1994. This made it possibleto open negotiations with the present and potentialscientif ic member countries with a view toconcluding contracts valic' from that dale. We arecurrently preparing fo. the signature of newcontracts with Austria, Spain and Swil/erland. It isclea.-ly with grea! satisfaction that ILL sees thereconstitution of the legal framework associatingthe countries, and hence the scientificcommunities, which share its operation and itsscientific life. It is also a strong motivation for thecontinuation of the operations necessary for therestart, covering the refurbishment of the reactor,the reinstallation of the instruments and theimplementation of the new structure of the ILL.

Since the removal of the old reactor vessel atthe end of November 1992. the emphasis has beenor. the preparation for the reinstallation. Theswimming pool has been completely cleaned, themechanical strength of its lining checked and itsgeometry ver i f ied. The state of cleanlinessachieved is remarkable, as the reactor teams canwork there without any particular protectivemeasures, and the inspections and tests reveal aswimming pool in a state very close to its originalcondition. No additional intervention work hasbeen necessary on the swimming pool. It is nowready to receive the new reactor vessel, whosemanufacture is proceeding according to scheduleand which should arrive at the beginning ofFebruary 1994. Before leaving the technicalaspects I will mention that the progress in cuttingup the old reactor vessel has enabled us toexamine directly the grid with the cracks whichled to the refurbishment, and to confirm thehypothesis proposed by ILL as to the appearanceof these cracks. All this work has been done underthe best possible conditions, thanks to thedynamism and competence of the ILL teams, andto the excellent spirit of cooperation shown byall those concerned with this project. Theadministrative procedure necessary to obtain thedecree to authori/e the restart is progressingnormally. ILL having forwarded the necessary

documents to the appropriate authorities at thedates specified, where they were examined bythese authorities, who are implementing the finalstages of the procedure. The progress of all theoperations, both technical and administrative, andthe expenditure situation, have been analysedregularly by the Subcommittee on Refurbishment.which concluded at its last visit to I L L onIN October 1993 that the costs and time scale havebeen respected up to the present, and that thereis no indication to suggest that the pk:nnui datefor the restart might not be respected.

As it is now almost certain that the reactor willrestart in mid-1994. it was necessary to launch theprogramme l'or reinstallation of the instruments.so that these would be available at the same lime.We are starting with the work in the guide halls,and shall continue with the installation of theinstruments in level C. which were completelydismantled to allow free access to the reactor, assoon as the beam tube thimbles have beenreplaced. To this end the ILL has to reconstitute asfar as possible the manpower required by recallingthe scientists and technicians who have beenwoi king in other research centres and laboratories.However we shall not avoid a difficult situation.as the ILL is now running in parallel two majortechnical projects, reactor and instruments, andcertain skills, which we cannot duplicate becauseof the staff limitations, are necessary for bothprojects.

A final event necessary for the future operationof the I L L was the introduction of the newstructure with four Divisions. This is theculmination of a long period of discussions andreflections initiated by the analysis of the ILL'sorganisation and operation carried out by aworking group at the request of the SteeringCommittee on 27 November 1993. The finalreorganisation proposal was accepted by theSteering Committee at its meeting in Abingdon on2 June 1993. and we wanted to implement it assoon as possible, so as to avoid the sensitiverestart period being affected by such a majorchange, and to ensure that the I L L is readyto operate within the new framework as soon asthe reactor starts up, as planned for mid-1994.The change of structure accordingly took place onI July 1993, very soon after the meeting of theSteering Committee. Although the ILL has beenoperating with the new structure since that date.

DIRECTOR'S REPORT

the corresponding staff complement has not yetbeen reached, nor has the final distribution ofpersonnel within the new units. The staff situationis still changing, following the first departuresunder the FNE early retirement plan, the return ofscientists and technicians who had worked at otherlaboratories during the shutdown, and finally thenecessary recruitments, particularly in thescientific sector. It is only during 1995 that weshall reach the staff of about 400 envisaged for thenew structure. Reorganisation of an institute witha limited staff level also implies internal transferswhich cannot all be effected immediately becauseof the current priorities which are not the sameas those of an institute operating normally.The departures and transfers which accompanysuch a reorganisation have a profound andsometimes disturbing effect on the networkof relations linking the members of anorganisation, and we should emphasi/e that in theILL's case this is taking place with theconstructive participation of the staff, who haveovercome the doubts and anxieties arising fromsuch a situation.

We have examined three points - reorganisation,reactor refurbishment and reinstallation of theinstruments - which are essential to permit thecomplete installation to start up in mid-1994, andto opérât^ as required with 5 cycles and25 instruments. We envisage two cycles in 1994.the first being devoted to the final adjustment ofthe instruments, and the second being open to theusers. Experiment proposals will be examinedby the Scientific Council subcommittees inautumn 1994, and we shall allocate the beam timefor a first group of 3 cycles, one in 1994 andtwo in 1995. This restart must be covered bya budget comprising the contributions ofthe Associates, as provided for in the Protocolto the Intergovernmental Convention and theMemorandum of Understanding signed on25.3.93, and by those of the scientific membercountries. These conditions are somewhatrestrictive, and for the lime being the ILL mustdevote its efforts to the return to experimentalactivity, while the development work has to beresumed more slowly. Under these new conditionswe shall only offer the users 25 scheduledinstruments. This is less than the number beforethe shutdown, and we are currently looking for aformula to permit the partial rescheduling of themissing instruments by negotiating conditions for

their operation with external groups capableof financing this operation in the contextof Collaborating Research Groups (CRGs). It isfinally a very positive sign that the ILL is startingto reconstitute its scientific sector staffcomplement, which had considerably diminishedin recent years. Eight young post-docs will berecruited in the early part of 1994, andrecruitments will continue until the end of 1995 toarrive at a total of 22 over the two years, whilethe first thesis students will start in October 1994.

We shall conclude this report by saying that inour view everything has been done to ensure thatILL resumes its scientific and service activities in1994, whatever the general economic situation.ILL is keen to reaffirm its vitality and itscommitment to the scientific communities whichsupport it. However the 1994 and 1995 budgetsonly provide for the return to operation, and do notyet permit the initiation of major newdevelopments. We should like to see a rapidimprovement in the budgetary situation, to enableILL to resume as soon as possible its role ofcreativity and development in neutroninstrumentation; this was not the least of theservices which ILL gave to the internationalcommunity

J. Rossat-Mignod, a member of the ScientificCouncil, died suddenly at the end of August.He had been responsible for the 'Service deMagnétisme et Diffusion Neutronique' at theCENG before becoming Director of theLaboratoire Léon Brillouin at Saclay. He was wellknown and highly appreciated by the internationalneutron community for his great competence.At ILL, where he had many friends andcollaborators, his death was felt as the loss of oneof its own members.

Jean Charvolin

BERICHT DES DIREKTORS

W a r 1992 das Jahr, das durch die Erklarung derI L L - G e s e l l s c h a f t e r . das ILL alsmultinationales Institut weiterl'iiliren УМ

wollen. gepriigt wurde, so war 1993 das Jahr, in demdiese Absicht durch die Unter/eichnung einesZusatziibereinkommens am 25. Mar/ in Paris in dieTat umgcset/ l wurde. Dadurch wurde dasRegierungsabkommen /wischen Frankreich,Deutschland und dem Vcreinigten Konigreich fiir eineDuuer von mindestens x.ehn Jahren ab dem 1. Januar1994 verliingerl. Dies ermoglichte die Aufnahme vonVerhandlungen mil den gegenwiinigen und moglichenweiteren wissenschaftlichen Mitgliedern iiber denAbschluB von Vereinbarungen 1'iir die Zeit nach dem1. Janiiiir 1994, Wir bereilen gegenwartig dieUnter/eichniing der neuen Vereinbarungen mitÔsterreich, Spaiiien und der Schwei/ vor. Fiir das ILList es selbstverstiindlich cine groBe Gcnugtuung, dieWiederherstellung des juristischen Rahmens /LI sehcn,der die Lander und damit auch die wissenschal'tlichenGemeinschat'ten verbindet, die an seiner Nut/.ung undseinem wissenschaftlichcn Leben beteiligt sind. Diesist auch ein wichtiges Motivationselement bei denArbeiten /.ur Vorbereitung des Wiederanfahrens, diedie Instandset/ung des Reaktors, den Wiederaufbauder Expérimente und die Eint'iihrung einer neuenOrganisationsstruktur am ILL umfassen.

Seit dem Abbau des alien Reflektortanks EndeNovember 1992 wurde der Schwerpunkt auf dieVorbeitung des Wiederaufbaus gelegt. Das Reaktor-Schwimmbecken wurde kompletl gereinigt. diemechanische Festigkeit seiner Auskleidung konlrolliertund seine Geometric iiberpriift. Das Niveau dererreichten Sauberkeit ist bemerkenswert. so daB dieMannschaften sogar ohne besondere Schut/kleidungarbeiten konnen. Die Kontrollen und Uberpriifungenzeigen uns ein Schwimmbecken. dessen Zustand demOriginalzustand sehr nahekommt. Zusat/licheArbeiten am Becken waren nicht notwendig. Es istsomit fur den Einbau des neuen Tanks vorbereitet.Dessen Herstellung geht wie vorgesehen voran. Milseiner Anlieferung wird Anfang Februar 1994gerechnet. Zum AbschluB der technischen Aspekte istnoch an/umerken, daB der Fortschritl bcimZerschneiden des alien Reaktortanks cine dirckteUnlersuchung des Gitlers mil den Risscn, die Ursacheder Instandsetzung waren, ermoglichte und dieBestiitigung der vom ILL zu ihrer Entstehungaufgestellten Hypolhese erlaubte. Allé diese Arbeitenwurden dank der dynamischen und kompetenten ILL-Mannschaften sowie des gulen Kooperationsgeistesa l l e r B e t e i l i g t e r an d i e s e m P r o j e k t/ur vollsten Zufriedenheil ausgefiihrt. DasVerwaltungsverfahren /.ur Erleilung der Genehmigung/um Wiederanfahren des Reaktors verlauft normal.

Das ILL hat die erl'orderlichen Unterlagen /u denvorgesehenen Terminen an die /ustiindigen Behordeniibermittell, die sic gepriifl und ininmehr dieabschlieUenden VerfahrensmaBnahmen eingelcilethaben. Der Verlaul' aller dieser lechnischen unda d m i n i s t r a t i v e ! ! Ma В n a h m en sowie dieAusgabenentwicklung werden regelmiiBig vomUnterausschuB "Reaklorinstandset/ung" kontrolliert.der anliiBlich seiner let/ten Sit/.ung im ILL am 18.10.93/.u dem SchluB kam. da!3 Kosten und Termine bis jetxteingchalten wurden und nichls darauf hindeutet. daBder vorgesehene Termin fur das Anfahren des Reaktorsnicht eingehalten werden koiinte.

Nachdem jet/.t praktisch davon ausgegangenwerden kann. daB der Rcaktor Mille 1994 wiederanlahrt, war es wichtig. mit dem Program m fiir denWiederaufbau der Instrumente /LI beginneii, damitdiese cbenfalls /ur gleiehcn Zeil /.ur Verfugung stehen.Wir h a b e n m it d e n A r b e i t e n in '.I e nNeutronenlciterhallen begonnen und werden uns imAnschluB an den Einbau der Slrahlkanale dcmWiederaufbau der Instrumente des Niveau С/uwcnden, die kompletl entfernl worden waren, uniZugang /.um Reaklor /u gewahren. Da/.u muB dasInstitut das notwendige Arbeitskraftepotential optimalwiederherstellen. indem es seine in andere Zentrenoder Laboratorien abgeoiclneten Wissenschaftler undTechniker /.uriickruf;. [Zinc schwierige Lage wirdjedoch nicht vermieden werden konnen, da das Institutgegenwartig /wei wichtige technische Projekte-Reaktor und Instrumente- gleich/.eilig durchfiihrenmuB und bestimmte Sachkennlnisse, die aufgrund derbegren/ten Stellen/.ahl nicht verdoppelt wcrdenkonnen, I'iir beide Projekte benotigt wcrden.

Eine let/te wichtige Vorausset/.ung fiir den/ukiinftigen Belrieb des Instituts war die Einfiihrungder neuen Struktur mil vier Abteilungen. Sie ist derAbschluB einer langen Phase der Diskussion und desNachdenkens, eingeleitet durch die Analyse derOrganisation und des Betriebs des Instituts durch eineExpertengruppe entsprechend dem Auftrag desLenkungsausschusses vom 27.11.90. Der endgiiltigeVorschlag /ur R e o r g a n i s a t i o n war vomLenkungsausschuB auf seiner Sit/ung in Abingdon am2.6.93 genehmigl worden. Wir haben Wert daraufgelegt. die Umstrukturierung so schnell wie moglich indie Tat um/uset/en, damit die schwierige Période desWiederanfahrens des Reaktors dadurch nicht belastetwird und auch urn sicher/.ustellen. daB das Institutnach Anfahren des Reaktors Mitte 1994 in diesemneuen Rahmen arbeiten kann. Die neue Slruktur wurdeam I. Juli 1993 -kur/ nach der Sit /ung desLenkungsausschusses- eingefiihrt. Wenn auch dasInstitut seitdem entsprechend seiner neuen Strukturarbeitet, ist weder die entsprechende Stellenzah) noch

В Ë RI С H ï DES DlREKTORS

die endgiiltige Verteikmg des Personals in don neuenArheitseinlieiten erreicht. Die Personalsitualionbefindet sicli in cler Tut in stiindiger Enlwieklung aïsFolge der ersten Abgiinge im Rahmcn der FNE-VoiTiihestandsregelung (FNE = Fonds National pourl'Emploi) und der Riickkchr der Wissensehafller undTechniker. die \viihrend des Reaklorslillslands inanderen Zentren und Laboratorien gearbeilet hallenund schlieBlich au с h wegen der nolwendigenEinstellungen, insbesondere im wissenschafllichenBereich. Ersl im Lan Го 1995 werden wir oinoPersonalstarke von uiigcfà'hr 400 Milarbeitern imRahmcn der neuen Struktur erreichen. DieLlmstrukturicrung cinés Institutes bei einer bcgrcn/lcnStellen/.ahl bringt auch inierne Umset/ungen mit sieh.die nient allé sol'orl durchgelïihrt werden konnen imHinblick auf die deiveitigen Prioritiiten. die niehtdiesel ben si nd vv ie die cinés Ins t i tu ts i mNormalbetrieb. Die Abgà'nge und Umset/ungen. dieciné solche Reorganisation in einem Uniernehmenbegleiten. haben tiefgreifcnde und mandimal MoïendeAusvvirkungen aul' dus Net/, der Be/iehiingen derBelegsehaftsmitglieder untereinandcr. Wir solltenenviilinen. daB in unscrem Fall das Personal aufkonstruktive Weise bei der Réorganisation mitwirktund die Zweifel und Betïirchtungen. die cine solcheSituation mit sieh bringt, /IL iiberwindcn wuBle.

Wir haben drci Punktc betrachtet -Reorganisation.Instandset/ung des Reaktors. Wicdcraul'bau derInstrumente- die wesenllieh sind. damit das gcsamtcInstitut seincn normalen Betrieb Mille 1994 wiederaufnimmt und sodann -wie vorgesehen- mit 5Reaktor/yklen und 25 Instrumenten I'ortset/t. 1994plancn wir 2 Reaktor/yklen, wobei der crstc Zyklusder Justierung der Instrumente dient und der /vveiteZyklus fiir Benut/er /ur Verfiigung stehen soil. DieExper imen t ie rvo rsch iage werden von donUnlerausschusseii des Wissensehaftlichen Rates imHerbst 1994 gepruft. und wir werden bei dieserGeleaenheit Strahl/.cit l'iir cinc crstc Gruppe von3 Reaktor/yklen -I Zyklus im Jahr 1994 und 2 Zyklenim Jahr 1995- vergeb'en. Die Bcdingiingcn l'iir dièsesWiederant'ahren miissen von einem Haushaltsiehergestellt werden. der sieh ans Beitragen derGcsclîschat'lcr -entspreehend dem am 25.3.93u n t с г/ с i с h n e (en Z u s a t / ti be re i n k о m m e n / u mR e g i e r u n g s a b k о m m e n u n d d e mVcrcinbarungsprotokoll- und ans Beitragen derwisseiisehaftliehen Mitglieder /usammenset/t. DièseBcdingungen sind / iemlich einschrankend.so daB das ILL der/cit seine Anstrengungen aul dieWiederaut'nahme der expcrimcntcllcn Arbeitkon/entrieren muB. Die Wiederaufnahmc derE n t w i с k 1 u n g s a r b e i t w i r d n u r 1 a n g s a mmoglich sein. Unterdiesen neuen Rahmenbedingungenwerden wir den Benut/ern nur 25 programmiertc

Instrumente anbieten konnen. das heiBt wenigerInstrumente aïs vor déni Reaktorslopp. Wir suehengegenwartig нас h einer Losung. die uns erlaubt. dieans dem Program m genommeneii Instrumenteteilueise wieder /u nul/en: /u diesem Zwvckvcrhaiidcln wir mit externen Gruppen. die fiir dieerforderliche Finan/icrung im Rahmcn von"Collaborating Research Groups" (CRGs) aufkonimenwiirdcn. iiber die entsprechenden Betriebsbedingungen.Ein schr positives Zeichen ist schlieBlich. daB das ILLunfiingt, seine Personalstarke im wissenschafllichenBereich /u erhohen. der in den let/ten Jahrcn starkgekiir/l wordcn war. Acht jungc promovierleWissensehaftler werden Anl'ang 1994 eingeslcllt.Die Einslellungen werden bis Ende 1995 forlgcset/l.In d'esen /vvei Jahrcn werden i i isgesamt22 Wissensehaftler eingestellt werden. Die erstenDoktoranden werden wir im Oklober 1994 begrù'Ben.

Zuni AbschluB dièses Beriehtes mochlen wir daraufhinwciscn. daB ans unserer Sicht allés getan wird.damit das ILL seine wissenschaftliche Arbeit undseine Dicnsllcistungen im Jahr 1994 wiederaufnimml.wie auch immer die allgemeine wirtschaftliche Lageaussehen mag. Das ILL mochle damit seine Vitalità'tbeweisen und seinen Verpfliehtungen gegeniiber denwissenschaftlichen Gemeinschaften naehkommen. DieHaushaltsplà'ne 1994 und 1995 erkuiben uns dieWiederaufmihine des Betriebs. sie ermoglichen unsjcdoeh noch nient die Inangrilïnahmc wesentlicherneiier Entwicklungen. Wir hoffen. daB sieh dieFinan/lage rasch verbessert, damit das Institut so baldwie moglich seine Rolle bei der Kon/eption und derEntwicklung im Bereich der Neutroneninstrumentierungwiederfindet. Und dies war nichl der geringste Dienst.den das ILL der internationalen Forschergemeinschaft«clcistct hat.

J. Rossat-Mignod. Mitglied des WissensehaftlichenRates, slarb plot/lich und unerwartet Ende August1993. Bevor cr seinen Posten aïs Direktor desLaboratoriums Léon Brillouin einnahm, war cr Leiterder Abteilung fiir Magnetismus und Neutronenstreuungim Keniforschungs/entrum Grenoble (CENG). Er warcin bckanntcr und von der internationalen Neutronen-Gemeinschaft wegen seiner ausge/eichnetenFachkenntnisse schr geschat/ter Wissensehaftler. AmILL. an dem er vicie Frcundc und Kollegen halte,wurde sein Tod wie der Verlust eincs eigenenMitarbeiters empfunden.

Jean Charvolin

ILL-ESRF-EMBL-COOPERATION

Relations with ESRF and EMBL

Following the establishment of a common site forEMBL. ESRF and ILL. reported in the last Annual Report,relations with the ESRF have continued to develop at themanagement level through direct contacts between theDirector of ILL and the Director-General of ESRF. and inregular meetings between the two Heads of Administration.

Two major developments on the common site are worthnoting. The EMBL has planned an extension to theILL/EMBL building (ILL20) to provide additional officeand laboratory space, with the possibility of eventual accessto ILL staff. Construction will start in 1994. Secondly, theESRF is constructing a guest house to provide sleepingaccommodation for visiting scientists. Some rooms will alsobe available to ILL visiting scientists.

A number of new agreements have been signed withESRF. including one on the exchange of technicalinformation and documents, and the establishment of acommon secretarial service for the theory groups of the twoInstitutes. These are in addition to existing agreements onjoint services, including the joint building, library, medicalservice, telephone, site security and restaurant.

At the .scientific level, many close contacts continuebetween the staff of the three Institutes on the site, includingthe development of an image plate detector for diffractionfrom large-scale structures, led by EMBL (see Chapter"Projects"). A joint ILL-ESRF Workshop on 'X-rays andNeutrons in the Study of Magnetism" was held on21-23 January 1993, which illustrated the great potentialcomplementarity of the two sources.

The Institutes have cooperated in two 'public relations'exercises locally. In June. ILL and ESRF look adjoiningstands at 'La Science en Fête' in Place Victor Hugo in thecentre of Grenoble: in November with EMBL theyparticipated in the 'Semaine Européenne de la CultureScientifique", including a joint press visit to the site.

The ILL and ESRF together continue to press for much-needed improvements in the provision of internationalschooling for the children of their non-French staff in localschools. They were founder members with local companiesof a new 'Association pour le Développement del'Enseignement International dans la Région Grenobloise'(ADEIRG). Good relations have been established with thelocal Education Authorities, which have resulted in someimprovements in communication with parents. A numberof issues have been taken up. including the questionof obtaining contractual terms to attract good foreign teachers.

Peter Schofield

- CO [ t EG ES -

The .scientific life of (he ILL is organised through the Colleges. The Colleges are the forum forscientific contacts and exchanges. The College Secretaries organi/e seminars and meetings.

The scientists have their hierarchical positions defined in the Science Division.In this respect, they are instrument responsiblcs and have the duly of dealing with more technical topics.As regards their scientific activities on the other hand, they are left with the utmost freedom, to chooseindividually their main fields of interest.

The College Secretaries are elected in June each year for u term of one year, which can be renewedfor a second year.

College Secretaries in 1993

College 2:

College 3:

College 4:

College 5:

College 6:

College S:

College 9a:

Theory

Nuclearand Fundamental Physics

Structural and MagneticExcitations

Crystal and MagneticStructures

Liquids, DisorderedMaterials and Metal Physics

Biological Structuresand Dynamics

Molecular Spectroscopy.Surfaces and Mesophases

Large Molecules

Spring

J.Voit

U. Mayerhofer

J. Kulda

M. Reeluiis (5a)B. Ouladdiaf <5b)

J.C. Cook

R.P. May

J.H. Williams

P. Lindner

Autumn

M. Fabri/io

J. Lu.,;

J. Kulda

G.J. Mclntyre (5a)B. Ouladdiaf(5b)

I. Anderson

L. Vuillard

Ci. Kearley

P. Lindner

The Colleges (except Theory) correspond one-to-one to the Subcommittees of the Scientific Council.The College Secretaries (with help from the Scientific Coordination Office. H. Buttner) prepare themeetings of the Subcommittees. They classify the proposals by subjects and collect advice on theirtechnical feasibility from the College members. In the meetings of the Subcommittees they actas secretary to the Chairperson. One experienced ILL scientist (if possible a Visiting Senior Scientist)per Subcommittee also attends the meetings.

COLLEGE 2

Theory

Members of the College

P, BaresS, Bra/o\skiiB. ClementsM. Fabri/toB. FourcadeF. GehhardA. (iogolinM. Kagan

General

C. MisbahP, No/ieresJ. PalmedP. QuemeraisS. ScheidlЛ. Valance.1. VoilM. Walker

The activity ol' ihe Theory College in 1443 has againbeen considerably affected by budget restrictions as sliounby the reducetl number of sialT in comparison with previousyears. 1 lie sinniltaneous growth of the KSRF Theory (iroup.«Inch shares ihe Joint (ll.l.-liSRF) Building with the II.I,Theory College, is a positive asset. gi\ing rise to 1'ruilfulcollaborations among ihe theorists of both groups.

During the year, the College composition has changedconsiderably: S. Bra/o\skii. .1. Voit. M. Walker and.1. Palmeri left: the first three returned to their own homeinstitutions, whereas .1. Palmeri moved to Montpellier «herehe obtained a CNRS position. Conversely, after October,lour new members joined the College: P. Bares (at ILL fortwo years). \:. CJebhard (for six months). A. Gogolin (tor oneyear) and S. Scheidl (also for one year).

Scientific activity in 1993The research activity of the Theory College concentrated

this year on condensed mailer physics, covering variousareas which are listed below. Special interest has beendevoted to "low dimensional" physics, ranging fromcorrelated fermion systems in reduced dimensions, tovarious aspects of surface physics, to the thermal behaviourof lipid vesicles and polymeri/ed membranes.

Helium and related topics

K. Clements investigated Ihe structure, stability,excitations and thermodynamics of thin films of liquid Heon weakly attractive substrates. This work has been done incollaboration with F. Krolscheck (USA). I!..I. Lauter (ILL),and M. Sarrcla (Finland). Experiments have shown thatthese films ean form well-defined atomic layers of /it/i/ii/4He. lying parallel to the substrate, and persisting ratherdeep into the him. Depending on the surface coverage, theirtheory predicts that superfluid He films, adsorbed on agraphite substrate, exist in both uniform and non-uniformsurface-covering phases. The transition between the twophases is first order, occurs near layer completion, and canpeisisi for at least three liquid layers. For a sufficientlysmooth substrate these layering-transilions should he

observed in torsional oscillator experiments. A lesspronounced layering structure is found for the alkali metalsubstrates, hut in the case of magnesium, at least onelayering-iransition should be experimentally delectable.

Thin films of "Mle adsorbed to a plane substrate alsopixu idc a unique opportunity to study Ihe structure of the"nearly" two-dimensional quantum liquids where, as thethickness of the adsorbed film increases, a transition from an"essentially two-dimensional" to an "essentially three-dimensional" system takes place. Using a generali/edFeynman theory, including multi-phonon scattering effects,they have determined as a function of surface coverage thedispersion relations, excitation mechanisms, transitiondensities, and panicle currents. A pronounced softening ofthe long-wavelength, lowest-energy mode is observed nearihe layering transition. Because of the layered growth, thefilm's sound velocity exhibits a series of oscillations. In amonolayer. the nature of the excitations undergoesa noticeable change at the coverage where the velocityof sound starts to tlct'i'Ciist1. This is a crossover from"essentially two-dimensional" to "essentially three-dimensional" behaviour. At long wavelengths, below(above) the crossover coverage, ihe lowest-energyexcitations are longitudinal pilotions propagating within themonolayer (surface excitations). At higher wave numbers,a layered-plionon level-crosses with a surface excitationto become the lowest-energy mode. For double- and higher-layer films, the excitations are complicated by multiple(layer-phonon with layer-phonon and layer-phonon withsurface excitations) level-crossings.

Pursuing a stimulating discussion with a visiting seminarspeaker (M. Liu), J. Palmeri began to reexamine the problemof the dynamics of the phase boundary betw ecu the A and Вphases of superfluid ''He. He has been attempting to settlethe question of what is ihe dominant friction mechanism onthe moving phase boundary.

P. No/ieres completed a work he started inspired by a setof lectures given some years ago. He has settled a questionnever clarified in the past: why does a condensate form in apure state and not within different degenerate states '.' Heshowed that it is the r.vc/w/w energy which makes the bigdifference, and which is lastly responsible for the pnrit\of Ihe condensait.

S. Scheidl has started a collaboration with D. Feinberg(CNRS). They intend to develop an improvedplienomenological description for materials where proximityeffects of metallic atoms between superconductive layers areimportant.

Correlated fcrmion systems

P. Quemerais and P. Bares, in collaboration withD. NuiKv-Regueiro (ESRF) and A. Bianconi (Italy), areinvestigating the possible existence of polaronic chargedensity waves induced by the interplay of strong correlationand electron-phonon interaction. This work has been

C O U EG F 2

stimulated by recent experiments on L;iT.4Si\Ni()4+s

coin pound s. \\hich suggest thai such a combined effectmight indeed he relevani in these materials. As a first step,they have considered a one dimensional model of polaronsin presence of strong on-site repulsion. Their aim is to get asmuch exact inl'ormuiion as possible in ID, before passing tothe higher dimensions relevant for the experiments.Although (he investigation is still in progress, thepreliminary results seem quite promising, especially fromthe viewpoint of a better understanding of the role ofeleelron-phonon interaction in nickclate compounds "iidhigh ^.-materials.

F. Gebhard and P. Bares are both experts on lowdimensional models solvable by Belhe Ansat/ methods.Bares has been investigating the possibility of applying thesemethods for solving a particular one-dimensional modelof light and heavy particles with local interaction.

Together they are trying to construct the eigenstales ofthe exactly solvable l/c-Hulibard model, which might lead toa generali/ation of the Bet lie ansat/ technique. Such a modelexhibits a melal-to-iiisulalor transition at half filling for afinite strength of the on site repulsion, in contrast to themore popular Hubbard model where this critical value is/его. The hope is to understand the origin and the relevantfeatures of the correlation driven metal-insulator transition,in order to construct more realistic Hamillonians whichmight show similar behaviour.

Gebhard is also interested in studying the link betweensingle-site and lattice problems for interacting electrons.Lattice Hamiltonians with a large number of nearestneighbours, or with a random dispersion relation, can bemapped onto single site models which may thus also be usedto study the Mott-Huhbard metal-to-insulator transition.

S. Bra/ovskii's research was devoted to several subjectsin the theory ot quasi one-dimensional (ID) superstructuresand of 1D models of interacting electrons.

He has, together with S. Matveenko (CEI) andP. No/ieres, addressed the problem of spin-charge separationin ID, by analysing current carrying stales in a system ofinteracting electrons, exploiting both the exact results knownfor the Hubbard model and the bosoni/.alion technique.He found that both spin and charge excitations carry currentsproportional to their respective momenta. In spite of being inagreement with a single particle picture of a noninteraclingI D Fermi gas, this result contrasts the spin-charge separationconcept as it is usually derived from the bo/.oni/.alion orfrom strong coupling arguments. For weak interaction, thisparadox is resolved by taking into account the Fermivelocity dispersion and by recxamining the current operatorstructure. For strong interactions he found an effect of holondrag by a spinon.

He has also investigated intrinsic defects in DensityWave (DW) crystals. For an isolated point (the 2n-soliton)and for a line (the dislocation) defect, he showed that the

Coulomb interaction dominates in determining distributionsof the phase ([>. of the potential <|> and of the accompanyingelectronic structure. The last shows itself e.g. in the collapseof (he DW state over a number of chains around (hedislocation. In spin DW conventional dislocations lose theirpriority in favour of a special topological object: a half-integer dislocation combined with a semi-vortex of thestaggered magneti/alion vector.

By reconsidering on microscopic grounds the effectsof the electric field on the phase dynamics and relaxationof CDW/SDW, he suggested a transparent form of thedynamic and dissipaiive equalion.s /or (lie DW phase and forthe electric field. His approach is based on a helpful relationbetween a "generali/ed condensate density" and a complexdielectric susceptibility ol intrinsic carriers. Separately lorCDW and SDW. he got the spectra and the attenuation forthe TO and LO modes, the low frequency relaxation and theintrinsic nonlinear conductivity.

M. Fabri/io has worked on (he behaviour of weaklycoupled one-dimensional chains of interacting fermions. Misaim was ;o understand how stable the peculiar one-dimensional behaviour is in relation to the switchingof weak transverse correlations induced by direct hoppingbetween the chains. He showed that the one-dimensionalbehaviour (so called Lutlinger-liquid behaviour) is quiteunstable as one couples chains together, since any weakinterchain hopping generates very strong correlationsbetween the chains, and he was able to determine whichcorrelations are favoured.

Together with A. Gogolin and S. Scheidl, they havestarted a study of the transport properties of quantum wiresin presence of diluted scattering centres. Since it seemsexperimentally crucial, their model includes an unscreenedCoulomb repulsion between the electrons. Therefore I ) theyinvestigated how Coulomb repulsion changes the responseof a one-dimensional band to an impurity potential; 2) theywill consider how the presence of more one-dimensionalbands (as it is usually the case in experiments) modifies thisscenario.

A Gogolin's research has been concerned with the theoryof quantum wires. In collaboration with N. Prokof'ev(USA), he studied the persistent current phenomenon bothfor interacting and non-interacting electrons. In the lattercase, in presence of a disordered potential, they were able toderive a universal formula expressing the persistent currentin terms ol' the transmission coefficient at the Fermi energy.In presence of electron-electron interaction, they showedhow an unusual si/c dependence of the current amplitudearises from the interplay of disorder and interaction.

P. No/.ieres continued his work on the behaviour ofheavy particles coupled to a light Fermi sea. This problem isof fundamental importance for the physics of heavyfermions and of many correlated systems. In particular, heshowed under what conditions the edge singularity producedby a .w/i.if/r and fixed scattering centre, persists if this source

COLLEGE 2

of scattering is left free to recoil. For a n<ni-/<n'«li:i'i/particle, lie proved rigorously that the singularity survivesonly in one, hut not in higher, dimensions; a result whichraises serious doubts on many of the theories proposed forhigh T\. superconductivity. Besides, he has beeninvestigating other related models, like the resonant levelmodel he studied !;>M year together with C. Varnia, whereessentially effective spin 1/2 channels interact withscreening channels, giving rise to a whole series ofinteresting phenomena.

Much of J. Voit's research interest was devoted tospectral properties of Lutlinger liquids, pursuing a studyinitiated in 1992. His investigation aimed at showing whereand which of the peculiar properties of Luttinger liquidsshow up, how they сип be measured and how theyinterfere/separate in any given experiment. Such propertieshave been clearly observed in a wide series ofphotoemission experiments on Bechgaard salts, which havebeen analysed by Voit in comparison with the existingtheors of Luttinger liquids. The outcome of this analysis isthat, in order to account for the experimental data, one isobliged to assume for these materials a model hamiltonian.which includes a long range interaction term. He has alsoshown how other very interesting features of L.ullingcrliquids (like the so called "spin charge separation") might beobserved in experiments where two particle correlations areworked out, as, for example, in inelastic neutron scattering.

Another field of Voit's activity was concerned withelectron-libron coupling in polyaniline. In collaboration withD. Baranowski (Germany) he obtained two importantresults, both connected to failure of Peierls' "theorem": (i) inthe strong correlation limit of the half-filled band, theyfound several phases with regular lattice spacing. Thisimplies that beyond a critical interaction strength thedimeri/cd Peierls state becomes unstable towards e.g. anideal pararnagnet. (ii) In the weak correlation limit atquarter-filled band, phases with long periods arc lower inenergy than the period-four Peierls slate. They will haveimportant consequences for the interpretation ofexperiments.

Continuing a collaboration with Anna Painelli and GianPaolo Borghi (Italy) on a new exact numericaldiagonali/.ation method for interacting electrons couplednon-adiabatically to phonons, they developed a newalgorithm, which takes advantage of the adiabatic basis ofthe problem, in order to reduce the critical memoryrequirements. They found some interesting new results, e.g.that, contrary to earlier wisdom, there are cases ofantisquee/.ing. i.e. where quantum fluctuations reduce theposition uncertainty of the phonons increasing themomentum uncertainty.

M. Walker began a collaboration with Keith McEwen(UK) to try to understand the nature of an apparentlyquadrupolar ordered phase of UPd^ He also completed workon the identification of the ordered phase of heavy-fermion

metal URiiiSii which exists below I7.5K. In addition, hecontinued work with graduate students on theoretical modelsfor the phase diagram of betaine calcium chloride dihydratc.and for the low-temperature hexagonal phase of Суц.

Surface physics

P. No/ieres devoted much of his !993 activity to thissubject, since he gave a set of lectures at the Collège deFrance on "Crystal \nrf<iccx: silrwitiri'. lluctiuitioiib. xrtnr/liand suability". Among the varioui aspects of this problemtackled in his lectures, some have led to new developments.In particular, he carried on research concerning: (i) themobility of a vicinal surface in connection with the recentexperiments on capillarity oscillations; (ii) Grinfeldinstability of a faceted or vicinal surface.

C'. Misbah investigated some problems connected tovicinal surfaces. He analysed the steady-state cellularstructure that may arise during step flow growth (growthfrom a super-saturated vapour, or by molecular beamepilaxi).

In connection with the problem of the competitionbetween noise and determinism in step flow growth, heextended the Burton-Cabrera-Frank theory to includefluctuations. He derived the non-linear stochastic equationcontrolling the behaviour of a single step, and thus he coulddetermine the range of parameters where fluctuationscompete with detcn;,inistic dynamics.

He also studied the behaviour ol linear fluctuations of atrain of steps. He derived the shape of the excitationspectrum of an asynchroni/ed train of steps. Asynchroni/.edfluctuations lead to qualitatively new effects. In particularthe time needed to form a bump on « step scales as/ (/ = interslep distance), while it scales like / "' fora synchrom/.cd train.

M. Fabri/io, in collaboration with E. Tosatli andG. Santoro (Italy), has studied a solid on solid model lor Ice(110) surfaces which can describe, depending on the valueof the parameters, rough, disordered and reconstructed (2x1)and ( I x I ) surfaces. They studied this model by mapping itonto a quantum spin-1/2 chain of Heisenberg type. Such amodel was then analysed both by numerical diagonali/.alion,as well as by analytical techniques. This allowed them toobtain a complete characterization of the phase diagramof the model.

Liquid crystals, lamellar eutectics, polymerizedmembranes and lipid vesicles

C. Misbah studied extensively the problem of growth oflamellar cutectics and liquid crystals. He discovered a newbroken parity-state, where, in contrast to the slate where bothlamellae are tilted in the same direction, each lamella has atendency to choose an opposite tilt angle to that of itsneighbours. He suggested new experiments to observe thisstate.

C O L L E GE 2

In connection with liquid crystals, ho tackled the problemol the coupling between the nematic-isotropic growing frontand the elasticity of the nenuitie phase, and he analysed it ina special geometry. He showed that weak growth speedcorresponds to weak coupling between those two effects,and the contrary for high speed. A part of this work wasdone with his student A. Valance, who obtained his Doctoraldegree on November 29th 1993 with a thesis entitled:"Contribution à la théorie dynamique de croissance descristaux liquides et des eutecliques lamellaires".

B. Fourcade has mainly worked on the behaviour of lipidvesicles. Phospholipid vesicles of high lopological genushave been observed in laboratory experiments. Thesesystems e.\hibit strong thermal fluctuations, and they differfrom the usual thermal undulations of the membranes. Theycan be described as positional fluctuations of necksconnecting to concentric membranes. Together with thegroup of Bensimon in Paris, he has introduced a modelbased on an electrostatic analogy. Such a model has beentested numerically and analytically and it shows that theholes or necks can move almost freely on these membranes.He is also investigating two component membranes (with aD.E.A-.studenl. T. Charitat), as well as budding problems(with another D.E.A.-sludent, G. Rudine).

During 1993, J. Palmeri began investigating anuncontrolled, but perhaps effective saddle point expansionmethod for going beyond the non-perturbative variationaltreatment that he developed with E. Quitter to studycrumpling transitions for self-avoiding polymeri/.edmembranes. Moreover, he attempted to develop a non-perturhative method that avoids the replica trick for studyingproblems with quenched disorder. He applied such amethod, which makes use of the so-called "principle ofminimum sensitivity", to the problem of directed polymersand manifolds in random media.

Other condensed-matter topics

M. Fabri/io, together with P. Carra (ESRF), investigated(theoretically), the possibility of using X-ray resonantinelastic scattering (XRIS) as a probe of charge andmagnetic correlations in transition metals and rare earths.Their analysis of the scattering cross-section relics on theapplication of sum rules, recently derived for X-rayabsorption and diehroism; it shows that XRIS might providea powerful new tool for obtaining new information onmagnetic and anisotropic materials.

P. Quemerais studied the growth of intermetalliccompounds with strong chemical order. He proposed asimple one-dimensional model of growth, based on anelectronic process, which is quite helpful for understandingthe selection and the propagation of a periodic orquasipcriodic chemical order during the growth process.This mechanism has been proposed as one of the importantphysical features for the comprehension of quasi-crystalgrowth.

Secretary: Michèle Fabri/.io

Elementary excitations in liquid 4He Films

B. E. Clements and H. J. Lauter

The structure, excitations, and growth of liquid 4Hefilms, adsorbed on a graphite substrate, are ofconsiderable experimental and theoretical interest. It isan intriguing goal to uncover the underlying mechanismsthat drive an apparently simple system to display acomplicated growth scenario [1,2], a multitude ofthermodynamic phases [3| , transient superl'luidbehaviour [4], and so forth. To understand thesephenomena one should first have a good understandingof the film's eljmentary excitations.

Neutron scattering experiments carried oui by Lauter,Godfrin, Frank and Lcidercr [5], done on lowtemperature films and for a broad range of surfacecoverages, reveal spectra that are rich with structure.In Fig. I, the experimental dynamic structure function,S(</, w) is shown for a 4He film adsorbed on a graphitesubstrate. It is well known that adsorbed helium filmsgrow initially by the formation of well-defined liquidlayers. Fig. I corresponds to a triple-layer liquid film.

"~.'ч

'•>'..

V "•» ».'«****, **•»*' »*-х*/****•*•*.•*•»•.«.».. Ir

fW£ — . . - — . . . ^

'^>чГ^!Ги"-*м'^СТ* •« * i t .

-::r.:-:-,:. ^-...»Г • •

_ -* ** ч . ••»» •^~**~"^'-"~~.*~--„ ,~«.4h«.. . *.„•»„.•"•-•"•.,..•.•.—-""П •"«. '* •

1.5 1.0 0.5fico (meV)

Fig. 1: The experimental S(q,w) for a triple-layer film(crosses). T/ге surface coverage is 0.239 A . The lowestand highest curves correspond toq~ 0.25 A'1 and q ~ 2.0 A'1

respectively. Also shown are the phonan-maxan-roton mode(:,olid curve), the surface mode (long-dashes) and a layer-plionon mode (dots) that level-crosses with the surface mode.

COLLEGE 2

The experiment was performed at the time-of-flighlspectrometer IN6. The scattering sample consisted ofHe adsorbed on graphite (Papex). which was kept al a

temperature of 0.65 K. The basal planes of the graphiteare in the scattering plane. Each experimental curve (thecrosses) corresponds to a different wave vector q. Thewave vectors range between 0.25 A and 2.0 A"1 andoccur at approximately equal intervals. The largest >vavevector corresponds to the position of the roton minimumin bulk helium. The S(</, w) have been verticallydisplaced for each ц to provide a clear representation ofthe excitations.

In the figure, additional curves have been drawn toindicate the positions of the various excitations. It isclear from the figure that, already for three layers, thereis a rather strong signal coming from a moiie that willevolve into the bulk pltonon-muxon-roton spectrum. InFig. 1 this mode is the highest-energy dispersion curve.The low-energy surface excitation (ripplon) is equallyclear from this figure. This mode is absent when thescattering is performed on a full cell. This provides proofthat this mode is indeed related to the liquid-gasinterface. There are two more important observations.First, between the phonon-roton excitation and thesurface mode there is i. plateau in the strength of S(q, w).The plateau is most obvious for the larger wave vectors.It appears that there is too much scattering to beexplained by the phonon-roton mode (whoseexperimentally determined maximum line width isobvious from the figure), the surface mode, and themultiphonon contributions. The latter, which are highlytemperature dependent, can probably be ruled out as apossible cause for the large plateau by looking atenergies above the phonon-roton mode. There it is seenthat multiphonon excitations produce very littlescattering at this temperature. Second, there is alow-energy, high wave vector mode with substantialstrength located below the roton minimum.

An explanation for the plateau and the extra mode isprovided by theoretical calculations. In closecollaboration with Eckhard Krolsclieck ofTexas A&M University, and Mikko Saarela of theUniversity of Oulu, a generalized Feynman theory ofexcitations has been developed and applied to thesesystems |6]. In Fig. 2, our theoretical S(</, w) is shownfor a triple layer 4He film on a graphite substrate. Theintensity of the mode is measured by the shade of thegrayscale. To keep the figure as clear as possible, wehave chosen to omit multiphonon effects here. FromFig. 2, it is clear that the theory predicts several modes.At short wave vectors the surface mode is thelowest-energy mode present. The theory shows that, forwave vectors below 1.5 A , this mode propagates on thesurface of the film and has a strong component of the

Fig. -: Мщ1 ofthe theoretical dynamic structure function.Vfc/.irj in h'eynman approximation for a triple-layer filmwith a surface covcmue iij'0.17 A'~. The dotted parabolic lineis the boundary, which separates discrete from continuumstales, in the Feynman theory. The darkness of the greysculeindicates /lie bcatterina intensity.

particle's motion that is out of the plane of the film.At high energies (15 - 20 K) a strongly coveragedependent mode has formed that will eventually becomethe bulk phonon-maxon-roton dispersion curve. Severalintermediate energy modes are also apparent. The theoryshows that these modes are "layer-phonons", i.e..longitudinal phonons that propagate within a given liquidlayer. Layer-phonons begin having significant strength atwave vectors around 1.0 À .

We have proposed that these layer-phonon modes areresponsible for the effects mentioned above.The possibility of seeing at least one of theselayer-phonon modes in the experimental data is evidentfrom Fig. I. A rather clear mode has been indicated bythe dotted curve in that figure. Similar to the theoreticallowest energy layer phonon, the experimental mode has adispersion curve that runs quite close to the surface mode- for intermediate wave numbers (cj ~ 1.2 A"1 ' it gives theexperimental surface mode a bimodal appearance.Interestingly, this mode appears to level-cross with thesurface mode at ц = 1.5 A , and for </ near the rotonminimum, where it has emerged out of the continuum,the full strength of the mode is shown. It is also veryconvincing that the sharp kink seen in the lowest-energymode, in Fig. 1 is very similar to the sharp kink observedin the theoretical values where level-crossings occur(</ = 1.5 A"'). In both the experimental and theoreticalS(q, w) the surface mode is no longer the lowest-energymode for wave vectors above the level-crossing. For theexperimental case, this is evident by studying the linewidth of the surface excitation through the level-crossing

С О i L Е С Е 2

region: below and above the level-crossing there is aclearly defined "shoulder" in S((/, »v) which is the surfacemode. In the theoretical analysis, we arrive at thisconclusion by studying the particle current below andabove the level-crossing. At wave vectors below (above)the level-crossing the lowest-energy excitation is asurface mode (layer-phonon). It is also clear from Fig. 2that there is the possibility of multiple (layer-phononwith layer-phonon) and (layer-phonon with surfaceexcitation) level-crossings. Finally, in the full-cell bulklimit, both experiment and theory show that thelayer-phonon mode has non-negligible strength andretains an energy lower than the bulk colon! The theoryshows that the luyer-phonon propagates in the first layerof the liquid-solid interface.

References

[ 11 M.J. McKenna, T.B. Brosius, and J.D. Maynard,

Phys. Rev. Lett. 69, 3346 (1992).

| 2 | B.E. Clements, E. Krotscheck, and H.-J. Lauter,Phys. Rev. Lett. 70, 1287 (1993).

(3| O.S. Greywall and P.A. Busch. Phys. Rev.

Lett. 67, 3535(1991).

|4] P.A. Crowell and J.D. Reppy, Phys. Rev.Lett. 70, 3291 (1993).

[51 H. J. Lauter, H. Godfrin, V. L. P. Frankand P. Leiderer, Phys. Rev. Lett. 68, 2484 (1992).

[6] B.-E. Clements, E. Krotscheck, H.-J. Lauter,and M. Saarela, in "Condensed Matter Theories",edited by J.W. Clark, A. Sadiq, and K.-A. Shoaib(Nova Science Publishers, Commack, NY, 1994),Vol.~9.

COLLEGE 3

Nuclear and FundamentalPhysics

Members of the Collège

P. AgeronH G. BornerW. Dre\elH.R. FaustG. FioniP. Geltenhort

External Members

K. Gobi-edit (ILL)V. Nesvi/he\sk> (PNPI)R. Oliver (ILL)"

Guests

Y. Chibano ( L'ni\. Sussex )D. Dubbers (I'niv. Heidelberg)R. Georgii (TU Mimchen)K. Green (RAL)P. lauljievdNRNE Sofia)P. Liaud (Univ. ChamberylY.Otake (Osaka Univ.)

A. Jungclaus.1. LastLI. MayerhoferM. PendleburyF. SchorrA. Williams

N. Ramsey (Harvard Unis.)S. Schiinert (TU Miinchen)К. Schreckenbach(TU Miinchen)К. Smith (Univ. Sussex)N. Vatin-Perignon(Inst. Dolomidu)

SummaryAs the only experiment at the ILL which took data

during the reactor shutdown the magnetic electronspectrometer from BILL continued to be used lor a precisionmeasurement of the ' 7 7Lu p-speclrum. BILL had beenmoved to the old PF1 site the year before. Another,different, heavy neutrino rearch experiment was performedin a collaboration with the University of Heidelberg.

Before coming to the ILL .1. Last had been involved inthe design of an electron pair spectrometer APEX (ArgonnePositron Experiment) to measure positron lines in "very-heavy-ion" collisions below the coulomb barrier. APEX wascompleted this year and started to take data. J. Last'scontribution to the experiment was the development of aposition sensitive Nal(TI) array for the APEX triggerdetector [ 11.

At the UCN facility PF2 work on the neutron ElectricDip.ne Moment (EDM/ experiment has continued.V. Nesvi/.hevsky from Gachina spent several months at theILL to study the systematic errors in neutron bottle life timeexperiments with the special emphasis on the MAMBO IIset-up.

The PN I upgrade was completed during 1943 withsuccessful testing of the ion optics of the new electro-magnet system with an re source. Current activities includefeasibility studies on the PIAFE project in which it isproposed to place a thermal fission source at an in-pileposition using the H9 beam tube.

The spectrometer (JAMS 2/3. after upgrading, has beenreinstalled al the C'-le\el of the reactor. The prototypeinterferometer GAMS 5T (Munich-ILL-collaboralion) hasbeen assembled and is currentU being tested. The newGAMS 5 spectrometer, which will replace GAMS I hasbeen designed. Its assembly will start in 1944.

During 1993 A. Williams and U. Mayerhofer weredetached to the ESRF with the latter rejoining College 3 atthe beginning of December. G. Fioni temporarily left theILL in July to work at the ISN on the PIAFE project. He willreturn to the ILL al (he end of January 1994. Therestructuring of the ILL also brought three new members toCollege 3: W. Dre.xel and P. Gellenbort who will beresponsible for PF2 and P. Ageron who is interested inexperiments with slow neutrons.

In memory of W. Mampe College 3 held a one daycolloquium on 29th January. 1993. His family, friends andphysicists met at this occasion to listen to talks whichcovered the broad range of Walter's scientific interests(See also the article by M. Pendlebury al the end of theCollege 3 chapter).

Scientific Highlights in 1993At the Cold Polarized Neutron BeamFacility PF1

Scientific activity al PFI in 1993 was almost entirelydevoted to two heavy neutrino searches. One of (hemcontinued to use the BILL magnetic spectrometer while theother one was done with a sealed down version of thesuccessful PERKEO neutron decay spectrometer.

The ILL collaboration with the Technical UniversityMunich continued to search for a heavy neutrinocontribution to nuclear [i-decay. First restricting limits forthe mass region up to 30 keV were established.Subsequently a new and improved detector system has beendeveloped and installed al the BILL magnet by S. Schonertfrom the TUM, It should now be possible to extend thesensitivity for heavy neutrino admixtures for up to masses ofseveral 100 keV.

In collaboration with the University of Heidelberg thePER КI NO (sic!) magnet was set up to measure the(i-spectrum of °S with silicon detectors using a virtuallyloss-free method originally developed for free neutrondecay. Our aim was to study the systematic effects whichelection backscaltering could have on the spectral shape inthe region around (he energy end point. The principle of theexperimental setup is shown in Fig.I. Various coincidenceconditions and energy cuts can be imposed on the data. Il isthus possible to extract the spectrum of electrons which arebaekscatlered from a silicon detector surface. These spectraperfectly agree with results from complicated Monte-Carlocalculations using the EGS4 program library (see Fig.2).As a result of the experiment we were able to set stringentlimits on the amplitude of heavy neutrino admixtures in the

COLLEGE 3

substrate layer200 A carbon foil

100 300 700channels

deposited electron energy in detector I

500 700channels

deposited electron energy in detector II

100 300 500 700channels

added energy signals from both defectors

/•V4f. / : The ['fini //>/<• <>t / rm-/nv /i-s/'<'< Inni'iifn: i'li'i'li'fni\ l'inilli'tlh\ //ic ( (nt\'t'r\ii>n l'Ii'citïtn \tfiiri с an' li'uftpcil />с/и ccn /ич> мН<'«пih'li'i'li>r\ h\ lin- iiiiifinctif liflil ami «ni. nr/ i al'lcr malli/ilchtl(°k\l'(lltCrilH!, !<>\f l'Hl'l'V\ <>lll\ Ifl llll' llch'l 1(1>Л. \\'lll'll ///(' \in^l('

\/'ci /ni ini/ilil/cl ni'f \iiinmcil c/c( ii'i>ni<4ill\' l/if hi/i (vui/i'i' tail

ili\ii/4><'ar\ tl'iiitiuni.

чинк- system which so Гаг hail produced the most signifiai!!!heavy neulrino signals (l'ig..1). We toiiiul llinl the energyspeclruni of electrons scattered from solid mailer couldcreate a heavy neutrino kink when superposed to the original(j-spectrum (l-ig.4). The results uere published in |2 | .

At the Ultra-Cold Neutron Facility PF2

Work on the current neutron HDM projecl using UC'Nat II.I. by the Sussex-K/M.-IU,-Washinglon-PNPIcollaboration has continued. The mercury magnetometerunder development has jus! recently reached the stage whereit has the required signal-to-noise ratio. The next step is tostudy its response lo high electric fields.

backscatteredspectrum

a) measurements

backscatteredspectrum

al Monte Carlo simulations1 ,

40 60 80 100 120 140 160 E (KeV)

l'ii;. -.' al McaMiri'ini'iil\ и/ I/it' initial ami llic Iwrkwillcrcilflfi /гни \/4'firinn; hi Moult1 Cai'/n \innilalioii o/'llic initialmill tin1 hat'k \( iiiit'ifii I'li't'irini \fn'i'trunr.

COLLEGE 3

l-'or the Mambo II project an intensive study lias been

carried out b\ I I . I . thesis student К Schorr and visiting

scientist V. Nes\i/he\sky to predict all the contributions I»

the measurement errors which vull arise when il is used in

future to measure the neutron lifetime.

This \ear saw the publication of the neutron lifetime

measurement Tn = 882.6 ± 2.7 s derived from the

KurchaUn Institute - ILL experiment carried out at the ILL

in I WO |3|. The experiment is shown in Kig. 5. It is the only

neutron lifetime experiment using UCN storage which has

used the detection of up scattered UCN at thermal energies

as \\ell as the direct detection of UCN. The storage vessel

hail \\alls of stainless steel coated with Fomblin o i l .

A reimnahle liner allotted the wall .surface area exposed to

the neutrons to he changed by a factor of about 2.5 where

this factor applied also approximately on a local basis over

all parts of the trap. lies i Jos changes of surface area,

measurements were made at room temperature and at -5.4 "C

where the l-'omhlin was fro/en. The delected neutron up

scattering rale compared with the number (if UC'N stored,

was used as a measure of the wall losses.

A number of talks on UCN were presented at the

Colloquium in Memory of Walter Mampe in January. One

of the most interesting problems discussed was that of the

much greater than expected wall losses for UCN in material

traps where steps have been taken to control surface

Imlrogen [4.51. Data for beryllium presented in the former

paper are shown in Fig. ft. Standard theory relûtes the losseson the trap walls to the total loss cross-sections and numberdensities of the wall atoms. These cross-sections can also bemeasured in other experiments using the transmission ofvery cold neutrons. Curves la. За and 4c show similar

increases with temperature which are consistent with what

can be expected for the inelastic up scattering of beryllium

and its increase with temperature. At the lowest temperatures

fit intervalfor polynomina

145 150 155E (KeVj

fit intervalfor polynomina

132 140E (KeV)

/•'l'v. 4: /\ppeann\cc <>/ a A/iiA in the sing/c tic/Mur spectrum dueto electrons huckscattcreil onto the délectai: and theoretical I'lloflieavv neutrino f.in( 1ч the </(//n / //.

Ht;. 3: Residuals <>l best fit of orihogimnli'ed polynomialsli> ^S fl-speclruni.

H)>. 5: Experimental layout. Il) Entrance gates of the guide for theiiltnicoltl lU'iili'iiiui: l2l iiii't'liiinixiii u'/i/c/i coiilrol\ the i>l<ile-\li4i>etlinlcl/ini/li'l tfdlc (> o/'llie Marnée vr.\xcl; (Jl i><itc oj'llie <letei-n>rnfiillrticiiltl nentnm.\: (4) the ilelectiir of the ultrueoUl neutrons;l.tf I/tin «I. I mini ti/iiitiiiii(iii diaphragm which \C[wnite\ the hif>li-vactium chamber of the storage vessel from the neutron guides;lf>) plate-xhiipedgntr; 17) \югаце vessel; IN) mixillian surface:14) outer vacuum jacket of apparatus; 1101 xcatterer \i-hich removes"siipcn rilical" iillracolii neutrons from the spectrum: III) coiledtithe for cooling the storage vessel; I /2) heater fur the storagevessel; 113) detectors of thermal neutrons which result fromineu/slic scalleriiig ofullrucold neutrons Itv Ihc .\tirfttce "/ thestorage ves \el: 114) cadmium shielding.

COLLEGE 3

100 200 300 400 500 600temperature (К)

/•lit. f>: > Itil AIIW'I/ lif: I Ли i/iiiiw'-WH.if/i'-rMiili'ivtl hen/Hum; 1 1 h I i/n'ruv'/nvi/ It'iiii't'riiliii'f i/i'/K'iii/i'iii'i1

о/ f/ii1 /n'nvYiiiiii li>\\ i iv>\\ wtinn f(T, + fT,,,J I'uli'ii/n/i'i/ in lilt'

(.?< I i/i'/Kumv/i \liihlrn ч! 11441. (/('.lidVM'j/P /I <i/ -.W O ;f.V) ((//-/)'<• №i/i. i/i'.ouM'i/fiS'/i (it MHI'Cl: (-/c) "\i>ln-ric<il"

shown, the dominant contribution to the loss cross-sectionshould he capture in béryllium. The value observed for curvela is consistent with the accepted value of Ч nib for thecapture cross-section. (The somewhat higher cross-sectionseen in transmission through the sintered beryllium sampleof cur\e ,ia is expected in view of the inhomogeneilvscattering). At Km temperatures, curse 4c from trappingexperiments shows a value which is approximately 100times greater than the capture cross-section. The absence ofup scattered neutrons suggests that the associated lossprocess in case 4с involves capture, at least at lowtemperatures. These enhanced losses amount to a probabilityof loss of 1-Й) ^ per wall collision.

M. Pendlebury visited Japan to see some projects onultra cold neutrons there. In particular the results ofexperiments on UCN production in liquid helium by downscattering of l> Л neutrons \\ere discussed [6|. The Yoshikifridge has been run on a cold guide at JAKKI. Up to now.UCN hu\e to pass out through the radiation shieldingwindows to room temperature regions before they can hedetected. As in the case of the fridge which has been run alILL. the passage through the windows seems to producelarger than expected losses. Measurements at ILL byphysicists from TU Munich. КЛ1. and HMI on up scatteredneutrons derived from UCN stored in the helium haveindicated that the number of UCN produced in the helium isclose to the number expected from theory. Now. Japanesephysicists are developing a scintillation detector for UCNwhich will work at 4 К with the aim of detecting the UCN

directly in the liquid helium. They are also starling to buildan instrument to measure the neutron LDM which will beconnected (a the frdge source and also operate at lowtemperature. A UCN fridge source operating on a cold guidelike 1153 at ILL should be able to accumulate UCN to adensity of about 2()()()cm •'.

At the PNI facility LOHENGRIN

Production rates of exotic isotopes alongthe ustrophysk'iil r-process path

Investigations based on data Iron) the Lohengrinspectrometer for far asymmetric fission of -'"'U (l:ig. 7) haveshown that a simple correlation can be established betweenthe yield and the reaction Q-value of the process. Thiscorrelation is exemplified in l-'ig. S and shows a linearcorrespondence if yields are displayed on a logarithmic axis:

The regression analysis gives а=О..Я44 and h=-45.X(>l.Here only ground stale masses are taken into account, theneutron binding energy from the thermal neutron capturereaction is omitted. The correlation coefficient for the datapoints between mass 70 and mass S7 is about 0.47. whichallows the calculation of yields to a factor of .4 if estimatesfor Q-v allies for exotic nuclei can he taken from tables.The strikins! feature is that the above relation holds over

/•ft;. 7: /wj|«/u'< milliiinl IIIM\ ili\lril>nlit>ii Inr itir ti\\'iiiiiiflric/mid» nl ' °{'In.II ll-i'iiin .1.1.. Sittn et ч!.. \i/cl I'ln v

j J.vV).

COLLEGE 3

almost 5 orders of magnitude in the yield, and (hut mostlythe estimate of exotic isotope production can he calculatedfrom an interpolation rather l inn un extrapolation in thegiven mass region.

From the above formula production rates of fragmentsfor the .standard PIAFK projects source (6..Ч kW thermalpower. 2.2-10 fissions-s ) (see chapter "Projects") havebeen calculated and compared to the expected productionrate for the planned Isospin Laboratory Project, based onspoliation induced by a I GeV, 100 |.iA proton beam in a1 Mol UC-larget (40 kW thermal power).

In Figs. Ч and 10 this comparison is shown for /.inc andgermanium. To correct for losses in the extraction andseparation stages Ihe production rales have been scaleddown to 4.5 ''<. The following features may be recogni/.edfrom the comparison: for very neutron rich species abovemass 70 and yields from fission are orders of magnitudeshigher than for spallation. and thus fission should be thepreferred reaction if a radioactive beam facility is to be built.The very reason for the higher yield in fission is, that i(proceeds cold, especially for far asymmetric fission. Thus,neutron evaporation is strongly suppressed, a feature whichis exemplified by the pronounced fine structure in the yieldcurves. In contrast, for spoliation it is known thai thisreaction is very efficient for producing neutrons byevaporation anil fragmentation, a fact which shifts the massdistribution curves to the neutron deficient side and washesoui any fine structure. The second advantage for fission is itsrather narrow mass distribution and the correspondinglyhigh yields for very neutron rich species between mass 70and 160. This strongly enhances the figure of merit whichputs the value of the usable intensity in the relation to theoverall waste created in any reaction. This ratio reachesabout 5 </< for the most abundant species in nuclear fission.

H. Faust spent 3 months at the Studsvik Labormory toestablish the principles for a standard PIAFE source whichcould be implemented in the H Ч beam tube. During his

3 -6<S> о

- -8=-10-12-14-16150 155 160 165

Q170 175 180

I-'tK. H: Correlation between the logarithm i>/ the yield far jarasymmetric jission to the mtclitm Q-vatue. The \lruixhl line is a fitto the data.

detachment to the ISN/Grenoble. O. Fioni was working oncalculations of the beam optics for the PlAFIf setupproposed at the ILL site.

At the PN3 facility GAMS

Levels above 2 MeV and the onset of chaos

In 1981. a detailed level scheme for 1(l8F.r. based onG A M S measurements was p u b l i s h e d | 7 |. The"completeness" features of this reaction led to a levelscheme that was complete for negative parity states upto about 2200 keV and for positive parity states to about2000 keV. It was thought prudent to halt the development ofthe l f i KEr level scheme at about these energies due to thedifficulties inherent in extending il into I he next energv

Ge-yield

76 78 80 82 84 86 88 90 92 94mass

Zn-yield

68 70 72 74 76 78 80 82 84 86mass

/•'/!>. V-K>: Rales for emtic ;inc ami germanium isotopes l'or иstandard PIAI-'K source compared to the IsoSpin laboratory (1SI.Iproject. In both cates tile production rates him1 been scaled downto 4.5 '/< li> account for the expected losses in the extraction andmass separation process.

COLLEGE 3

region aiul to the desire to preserve the completeness

property. These results formed the basis for ;i number of

sueee.ssful tests of the 1BA model and the completeness of

the scheme has made this nucleus a touchstone testing

ground for subsequent experimental and theoretical work.

Recently, the original 1481 data have been further analy/ed

and new dam were added in order to propose a considerable

extension of the level scheme along with rotational hand

assignments up to energies (well above the pairing gap) as

high a.s nearly 2800 keV |8|. These data were used to argue

that there is a distinction in intensity for final stales of low

and higher К |K=0,1 \s. K=2-5) and therefore to conclude

that К remains a good quantum number in the neutron

resonance energy regionwith an excitat ion energy

Нч ~ 7-8 MeV |9|. This conclusion, which is contrary to the

usual perception that this energy regime is chaotic at low

spin and that the neutron capture levels arc complex

compound nuclear states, has aroused considerable interest.

In order to further elucidate this situation we have carried

out extremely high statistics y - y coincidence data for l h N Kr

f o l l o w i n g thermal neutron capture on " ' 7 Hr. These

measurements were carried out at the I5NL-reactor. Our

results alter considerably the experimental and theoretical

work on l f l l S Kr cited above and affect the conclusions

concerning the quality of the К quantum number in the

neutron resonance region: The claims that К remains good

and thai this energy region is non-chaotic are shown to be

based in part on bund assignments that need to he seriously

re-examined.

Interpretation of GRID profiles

First principles Molecular Dynamics ( M D | simulation

were further developed to describe G R I D prof i les

(Rossendorf-ll.L. Helsinki-ll.L collaboration). The study of

Gamma Ray Induced Doppler broadening alow s to obtain

insight into the slowing down process of atoms in solids as

well as information about short lived nuclear lifetimes. The

new calculations (an example is shown in Kig. 11 ) show that

directional correlations in single crystals can provide

information about the site in which specific atoms are

located in the lattice. With these theoretical treatments

we expect to develop the basis for new GRID-measurements

to be carried out after the reactor restart.

Secretary: Jiirgen Last

References

11 ! N. Kaloskamis el al.. Nuel. instr. Melh. A330.

447-457(199.4).

|2| H. Ahele el al., Phys. Lett. B3I6. 26-3К 1993).

|3| W. Mampe el al., JETP Lett. 57. 82( 1993).

|4| V.P. Alfimenkov et al., JETP Lett. 55, 84 (1992).

|5| S.V. Zhukov el al.. JETP Lett. 57 (1993) 464.

|6| H. Yoshiki et al.. Phys. Rev. Lett. 68, 1323 (1992).

|7| W.K Davidson el al.. J. Phys. 67. 455 ( 1981 ).

|8| W.K. Davidson and W.R. Dixon. J. Phys. 617.

1683(1991).

|9| J. Reksiad et al.. Phys. Rev. C47. 2621 (1993).

сОи

-800 -400 400 800

!чц. II: l-.\4ini>lc\ /or l)ni>pli'r-hrtHitlciH'il linc\hii/>e\ tine In lilt1 \lin\iiif; iliwn />/ тч>Н\ in пнннк'П'МнШнг \ilicon. The Dtipiiler-hniiulened/i'iic\/w/>cs an' />mlh it'tl h\ Ml) \imul4tii»i\ fur ihe \i.;nul<in y-tlefin with I: ^ = 2.43 Me\' Jtilluwinx the mn-lnir rraclion •'s.SVfii.yr".SV./Vic \inn4nre in rile linr\hapv reflect** the dependence <>/ lite *,/imini; </тгн/>гнсс\\ i>/ the recoiling nuclei <m the recoil ilirectitm in the rrv.vfn/.With с/шикни; tilitinmi'iit* hriui'en tlir \i>fi'lri>iiit'ifr <ais anil l/ic ivvs/u/ urit'iiltilinm lilrimlctl in llu1 fiqiirel the liin:\h(t[>r changesHih\taiilitill\. Tin' iiin\i'r\iil /uilfnlidl Ininrkeil lin<.'\t unit the Mu/tei'c />i>leiilitil llhin liite^t recall in ili//erenl ///«'S/K//ICA which shmilil he('\[>crinicnt(ill\~ I'eMih'eahle. The ctilcitlcilitni^ \vere <lone h\ A'.//, tfcini^. Hi^^entlin't.

C O i LEG E 3

One Day Colloquium in Memoryof Walter Mampe

On the 24th of January. IW3 physicists and friends cametogether from all parts of the world to join in rememberingWalter Mainpe and discussing the field of study which hadinspired his research. They did this in the presence of hisimmediate family and bore witness to the immense regardthey had for Walter in both personal and scientific domains.In all. some 1 15 persons attended.

Walter being a most energetic and outgoing individual,had contributed significantly to very many collaborations,too many to present them all in a one day meeting. Theprogram was therefore concentrated on those topics whichthe organisers felt hud been closest to his personal interestsand which had stimulated his original contributions.

Peter Armhruster. who was recently a director of ii.i. andone of the organi/ers of the colloquium, opened thec o l l o q u i u m and i n t r o d u c e d the I'irsi s p e a k e r .Norman Ramsey who had worked regukirly with Wallet-over the last 18 years. Professor Ramsey gave his lively andmoving personal recollections of Walter as a colleague andparticularly as a friend, both at work and at leisure. He wenton to describe Walter's scientific career highlighting manyof the projects with which he had been concerned. Walter'swork began with measurements in nuclear physics madewith the beta spectrometer in Munich where his thesissupervisor was Till von Kgidy. Till gave the second talk inwhich he traced a path, from the time when Walter was hisstudent, to some of the most recent developments in nuclearphysics concerned with the question of when nuclear slatesare chaotic and when they are not chaotic and by whatcriteria this can be judged. The ideas have, been developedusing the data that have been accumulated by the wideranging efforts of nuclear physicists over the last fewdecades. The BILL electron spectrometer at ILL was anoutstanding machine making a notable contribution. Walterworked for three years on the development of BILL amiafter he had completed it in 1474. he became the first personresponsible for its regular operation for v isiling users. A yearlater, when BILL was well established, he handed over toKlaus Schreckenbaeh. Klaus described some of hisexperiences then. The spectrometer weighed 7 Ions andstood 3 m high with parts which extended deep into thereactor. It was a big responsibility, lie could not help hutremember the remark within some pages of operatinginstructions where Walter had written laconically. 'If youhear by any chance a loud bang from the 150 A. 200 Vpower supply, that is. unit 10, and you see а Пате comingout of it. you are sure that you have made a mistake'. Inspile of such dire warnings, ihe whole instrument workedextremely well with incomparable energy resolution formany years. Klaus recounted how. in addition to itsproductivity for nuclear physics, it had been the idealmachine for many experiments in fundamental physics, thefield to which Waller had then moved.

Walter's first project in this new area was a precisionmeasurement of the neutron magnetic moment. Il involvedworking closely with, among others. Harvard thesis student(ieoffrey Greene. At the successful conclusion of the projectwhich reached a precision of 2 parts in K)7. both werestimulated to pursue this kind of work. Geoff was present todescribe that first project and more recent fundamentalconstants experiments with neutrons which still involvethe ILL. As an outcome Waller became committed to slay atthe ILL lo become a Stall Scientist in fundamental physics.

Immediately he began to supervise his first thesis studentRoland Cahier and lo he involved with a series of beautifulexperiments in neutron optics described in talks by Ciahlerand Anton Xeilinger. Also at that lime ( 1477) ihe first ultracold neutron source came into operation introducing a fieldwhich immediately became Walter Mampe's principalresearch interest anil the theme of an ongoing collaborationwith ihe author, others, and in particular. Paul Ageron whotalked about all the UC'N developments at Ihe ILL. The I'irsicollaborations concerned (lie neutron electric dipolcmonie.nl. described by Ramsey and taken up again bvBoh (ioliib who spoke about UC'N production in superfhmlhelium ;.nd new ways in which liquid helium might be usedlo measure ihe electric dipole momeni with even higherprecision in the future.

Another of the very early UC'N projects was themagnetic storage ring for neutrons described in the talk byProfessor Wolfgang Paul. In its later version of 1ЧХ7 themagnetic storage ring was se', up at the new ILL UC'Nsource on level D which incorporated the use of the ILL coldsource with the turbine of Albert Steyerl. By this time thestorage ring hail been developed to the point of giving one ofthe best neutron lifetime measurements. When its largesuperconducting magnet was in operation, data was takenunder personal supervision both day and night andWalter Mampe's input was considerable. Besides his workwith UC'N. Walter also had responsibilities for experimentsvvilh cold neutrons such as those on the neutron decayangular correlation coefficients which were described byTom Bowles from Los Alamos National Laboratory whereWaller had been a visiting scientist. The results of thoseexperiments are combined with the neutron lifetime value togive the basic parameters of the weak interaction ol thenucléon al low energies.

In addition to greatly smoothing Ihe way for these manycollaborations. Walter had his own projects which started atthe first UC'N source where he studied the storage ofneutrons in traps with very clean surfaces so as tounderstand heller the loss processes. Later these projectslead naturally lo a program of experiments lo measure theneutron lifetime by storage in material (raps. Out of thisgrew a very fruitful friendship with Chris Bales who haddiscovered the high efficiency of Fomblin liquid «alls inremarkable experiments at the small reactor in Risley nearManchester. Driven vvilh much skill and determination byWalter, ibis program ol" experiments resulted by 14X4 in

С О L L Е С Е 3

\\luil was, al the lime, the mosi précise neutron lifetimemeasurement of SS7.d ± .vl) s. Two vcars lui or. Kussiancol leagues, for whom Waller hail a spécial regard, were ablelo make lifetime measurements wilh similar precision inRussia and these were in good agreement with those of ILL.Their program and iheir reiniiiiseenees of limes spent witii\\'alter were presented vividlv in ihe talks In AnalolvSerebrov. l.e\ Bondarenko and Vasiliv Moro/ov. Themeasurements al (iatehina described h\ Tolia had employeda verv cokl Irap \\ith beryllium or solid oxygen surfaees.Lifetime experiments with nialerial traps ha\e to hedesigned so thai llie extraneous wall losses can he correctedfor with high precision. The original aim of the Gatchinaexperiments had been to a\oid Ihe problem In reducingthese wall losses to below one tenlh ol one percent ol Ihehela decay rale. To iheir snrpri.se. ihev could nul hring ahoulsuch a largi' rcduclion. Thev achie\ed losses of 3 4.compared vviih 15 '< in ihc l-'omhlin traps, nevertheless,gnen the flexihlc nature of ihe Cialchina apparatus, a goodhleiitne measureineni has resulted. Why ihe losses remainahoul one hundred limes grealer ihan anticipated remainspu//le. in spite of considerable suliset|iienl thought andexperimentation. Vasiliv Moro/ov described separateexperiments al ihe Kurchalov Institut aimed al furtherelucidating loss mechanisms on clean surfaces. These ha\ealso re\ealed unexplained enhancements. In the earls years,large losses were found lo he linked to Ihe ubiquitouspresence of hydrogen. B\ now il is thought lhal (his isunderstood and under control through vacuum haking andcooling procedures. Perhaps ilie.ro is some other featurecausing surprises!

There is much lo learn vel in the physics of particles aswas emphasi/ed by Dirk Duhhers in his lalk which reviewedten fundamental questions thai neutron experiments cancontinue to help lo resolve. Thus the colloquium lookedforwards as well as backwards, and in his concludingremarks Ken Smith expressed the feeling of gratilude ol' allthose present for what Waller Vlampe had contributed in somam different ways to promote Ihe ongoing collectiveendeavour.

Mike Pendlehun

Scientific opportunities with the fundamental physicscold and ultra-cold neutron sources

Jiirgen Last and Mike Pendlebury

Already home of high intensity slow neutron beamsbefore 1991, the ILL will, after the reactor restart, offerto the fundamental physics community two uniquefacilities with the highest eold and ultra-cold neutronfluxes currently available. Both facilities, PF1 and PF2,are scheduled to begin their regular operation after aninitial test and commissioning phase towards the end of1994. In the following we will diseuss the lay-out andscientific perspectives of the eold neutron beam facilityPFI and the ultra-cold neutron source PF2 (TGV).

PF1: The new and enhanced cold neutron beamfacility

When in 1990 SN7, then still located at Ihe far end ofthe old neutron guide hall, was again given the status of ascheduled instrument, it was only to operate a few morereactor cycles under its newly regained name PN7. Untilthe reactor shutdown, after nearly 20 years of operation,this facility featured one of the most intense cold neutronbeams in the world with an equivalent capture flux of

ф=3-10 n-cm"~-s" and, after the installation of one ofO. Scharpf s super-mirror polarizers with polari/.ationstrengths regularly between P=0.96-0.98 at<j>jjol=5-108 n-cm"--s~', it had the highest figure of meritР~-фр0|. Experiments at PN7 also benefited from therelatively low background rates due to the 110 m long,slightly curved neutron guide.

In fundamental physics the use of cold neutrons isoften preferable to thermal neutrons. Al intensitiescomparable to those of thermal neutron beams, coldneutrons are typically 4 times slower and thus remainlonger in the measurement volume. For n-decayexperiments this immediately results in a 4 times highercount rate. In the energy range of cold neutrons thecapture cross-sections follow strictly the 1/v dependence.Thus slower neutrons have enhanced capture probabilityand avoid complicated resonance corrections inexperiments that require high precision beam calibration.Also a slower neutron beam can be polarized to morenearly 100% and the polari/ation vector more easilyturned into any direction by a simple magnetic guidefield.

All these advantages were reflected in the highdemand for beam time at PN7 which was usually three tofive times more than the available reactor time. There isa wide spectrum of scientific activities with a significantproportion of experiments on free neutron decay, wherewe count 4 lifetime and 3 correlation coefficientmeasurements. Another large group of experiments

С О LL Е G E 3

measures parity violating features in neutron nucleusinteractions. The latter included processes like nuclearfission and n-y reactions after polari/.ed neutron capture.

Over the years the PN7 beam quality becamedegraded due to the introduction of several interruptionsin the H14-2 guide and deterioration of the natural nickelcoated guide itself. To partly remedy this situation, it wasproposed in 1992 and subsequently decided to rebuildPN7, which meanwhile had become PF1 for EhysiqueFondamentale, at the end position of the H53b guideinside the newer guide hall ILL22. The same location atthe 5 8 Ni coated cold neutron guide which had beenformerly been used by the n n collaboration.

The primary H53b guide ends inside the "EVA"casemate. There it has a usable cross-section of 6 by12 cm", a fourfold increase over H14-2. It follows a 4 mlong s i iNi coated guide segment with the same cross-section which will guide the neutrons into the PFIcasemate and to the polarization set-up. Measurements ofthe n n collaboration established a capture flux ofH O 1 0 n-cm"2'S~' and we hope that this number can bepreserved. Thus one can expect at best a total fluxincrease of about one order of magnitude. Experimentalset-ups which cannot take advantage of the significantlyenlarged beam cross-section will only benefit from the3 times higher capture flux.

PFI will offer considerably more space to the user.The experimental area, now securely protected by a wallof concrete blocks is 4 m wide and 8 m long. This willsimplify TOP measurements. Adjacent to theexperimental zone, an area 4 by 4 m2 is available forexperiment preparation and testing so that an experimentcan be set up while there is still another experimenttaking data. This way we hope to reduce the loss ofvaluable beam time in the set-up phase.

In these years occupied by the ILL reactorrefurbishment, the fundamental physics community hastried to perform experiments which were originallyscheduled for PN7 at NIST, Gatchina or elsewhere.Others have used the time to design and build completelynew experiments. There are plans for at least 4 differentnew measurements of angular correlations in neutrondecay. These experiments alone will keep PFI busy fortwo or maybe three years. There are also proposals fornew experiments on parity violation in nuclear systems,that can now be carried out at higher count rates and withbetter statistics. Also crucial for the understanding of thestructure of the fundamental interactions are time-reversal invariance (TRI) measurements, and there arealready two new proposals in this class for PFI. Whetherthe neutron life-time will ever be measured again in a

beam experiment at PFI is an open question. It seems asif ultra-cold neutron techniques are more suitable forsuch measurements.

Last but not least we expect a number oftechnological developments to be made at PFI.A neutron focussing device which should give a factor 5flux increase on a 1 cm" "hot spot" is already underdevelopment. Also, the significant "contamination" ofthe НйЗЬ beam with very cold neutrons of wavelengthsgreater than 9 A could be extracted with a suitable beambender. Such neutrons can be used to feed a future supra-thermal source for ultra-cold neutrons or in neutroninterference experiments.

PF2: Ultra-cold neutron source TGVand experimental facility

The ultra-cold neutron (UCN) source assembly onlevel D comprising a vertical guide from the cold sourcefeeding the Steyerl turbine (TGV) was commissioned inthe autumn of 1985 and was in regular use early in 1986.The major input of finance and technical effort wasprovided by the TU Munich while much closecollaboration and technical work was also required fromthe ILL Reactor Division.

Until this year the source had the status of a specialinstrument for which the TU Munich was responsible.Recognizing the increasing demand for and interest inUCN, the ILL has decided to make this a scheduledfacility and has assigned the instrument name PF2.Accordingly a leasing agreement has been made withthe TU.

At the commissioning in 1985 the number density ofunpolarized UCN with speeds less than 6 m/s at theposition of the experiments, which is about 4 m from theturbine, was found to be 50 cm" 3. This was ahundredfold improvement compared with the earlier ILLSN5 thermal source for UCN, a change whichcompletely transformed the experimental possibilities. Itremains at present the world's strongest source of UCN.Another excellent feature of the source has been itsnearly constant UCN output level over the five years ofrunning since it was installed. In fact no serious troublewas encountered until a small leak in the vertical guideappeared just before the shutdown in 1991. The TGVguide also provides a beam of 100 Л neutrons with awavelength resolution of 20 %, which are being used forthe development of a long wavelength interferometer.The next strongest UCN source is that of the WWR-Mreactor at PNPI, Gatchina near St. Petersburg. After therenewal the PNPI source reaches about 1/3 of theintensity of the ILL source but its output tends todecrease in time so that the average has been 1/5.

С OLLEGE 3

Anticipating the arrival of the new UCN source theneutron lifetime experiment organized by W. Mampe,employing Fomblin liquid coated walls, was rebuilttaking account of the experience gained from apreliminary trial on SN5. The measurements werecompleted by the end of 1988 yielding a lifetime resultof 887.6±3.0 s, which at that time, was a threefoldimprovement in precision compared with any otherpublished result. By then, the systematic error was threetimes the statistical error; further progress would requirea more elaborate apparatus. A related lifetimemeasurement then took its place combining ideas fromILL and the Kurchatov Institute. This was completed in1990 with the result 882.6±2.7 s. The world average ofneutron lifetime results published since 1987 is886.211.6s.

The neutron electric dipole moment measurementwhich had reached a statistically limited error of 3-l()"2S

e-cm running on SN5 between 1982 and 1985 wasmodified slightly and transferred to the new UCN source1986 where it ran until 1989, reaching a statistical errorof 2-Й)"26 e-cm. It too had become limited by systematicerrors which were, by then, double the errors fromcounting statistics. Nevertheless, close to one order ofmagnitude improvement and another world minimumerror had been obtained. For the time being at least thehigh intensity UCN source had won, causing two largeexperiments to withdraw to adopt a more advanceddesign. In both cases new instruments have been builtand new measurements are planned at PF2 for the timewhen the neutrons return.

The high UCN intensity has also made it possible todevelop a versatile monochromator for UCN. Gravitywas used to select and control the energies and thedevice has been used to make the most precisemeasurement to date of stored UCN loss rates versusUCN energy. It has also confirmed a slight warming ofthe neutrons after long intervals of storage which hadalready been suspected from storage data from the liquidwalled trap. This may be explained by environmentalvibrations which must be shielded against for the nextlifetime experiment.

The feasibility of using UCN at PF2 to measure theelectron asymmetry in polarized neutron decay A is alsounder study. As part of this exercise there are plans totest whether a simple superconducting magnet fieldconfiguration can be used to generate essentially 100.0 %polarization in UCN and if so, to what extent this highdegree of polarization can be maintained during storagein a material trap. The signal counting rate for anasymmetry experiment will be less than in cold beamexperiments such as PERKEO II, but there may beadvantages in respect of background and polarization

measurement. The subject of anomalous losses of UCNdiscussed on an earlier page must be pursued with moredetailed experiments at higher flux. Applications to usePF2 have already been received.

Most of these experiments only need to be suppliedwith UCN for intervals of a few seconds with gaps of asmuch as thousand seconds in between. It is ideal forrunning experiments in parallel using a switchingsystem. An associated problem is working space. Theprincipal investment planned for adapting PF2 better toits future role is for extending the beam swi'ching systemand for extending the floor area available tt> experiments.

COLLEGE 4

Structural and MagneticExcitations

Internal members

T. lîaumbach

S. BramwellT. ChattopadhyayR. С шта1

Ch. DollH. DnrncrB. Farago

I-., Garcia Maires y Cortes.1. Kulda

F. .(mull members

M.AIha(CI-N(i).1. Uossy (CNRSl(J. Dolimxl'JF)C. l-'ilippini (CNRS;15. Fak(CLNG)

Introduction

H..I. LamerЛ. MagerlA.P. MuraniH. MulkaS. Ponyol(). Schaorpl'li. SchmidЛ. SeveringC.M.I-. /even

P. MoneeautCNRS)I .P. RegnaulilCHNCi)II. SchobcMCHNG)M. Vallade(l'JF)Ch.VeliierlF.SRF)

The scientific activities of College 4 went on throughanother year ol' the II.1. reactor shutdown without asignificant reduction of their scope. Despite the absence ofneutrons, college members pursued their research projects,combining theoretical work and data evaluation al ILL withneutron experiments at other reactor centers. LaboratoireI.eon Urillouin at Saclay and the Japan Atomic HnergyResearch Institute I.IAKRI} at Tokai. Japan, played aprominent role in providing beams of sufficient flux for I he-nine consuming inelastic scattering experiments. In the caseof JAKRI. a generous l-'oreign Scientist Invitation Programpermitted four college members lo bridge the large distancefrom I'urope to Japan and to carry out several weeks"experiments each. The preliminary results of three of themare mentioned in \\hal follows.

Scientific Trends and Highlights in 1993I'honon eigenvectors in silicon

A number of existing phenomenological models oflattice dynamics of silicon has been recently complementedby the potentially more exact results of «/> initia calculations111. Although most of the different approaches reproduce theobserved dispersion relations uilh comparable accuracy.significant differences exist between the piedicledeigenvectors, drawing attention to their direct experimentalobservation.

In a series o| experiments performed during !W2 and

on the TAS I spectrometer at the .IKK i leaetoi ol

JAI'.RI l.iapan Atomic Fnergy Research Institute. Tokai.

Japan) the problem of determining phonoii eigenvectors

from the observed intensities ol coherent inelastic scattering

was revisited | 2 | in preparation for luiure activities ol ibis

type on the TAS instruments at ILL Only scan geometries

fulfilling the conditions for good resolution have been

employed so that the observed peaks could be resolved from

the spurious ones. The inelastic structure factors were then

extracted from the complete set of integrated intensities,

observed at different Q and d> values, via a single scale

factor analogously lo the current practice in crystallography.

1-ig. la displays observed dispersion relations for the 1 |

acoustic anil optic branches along |l l()|. As a consequence

of an accidental degeneracy llieir polari/alion is elliplica1.

passing from purely longitudinal | I l()| at the Hrilloum /one

origin lo purely transverse |l)(ll | at the /one houndar_> lor the

acoustic branch and \ ice versa lor (he optic branch, l-'min llic

siruclure factors, l-'ig. I b. measured in ihfferenl Urillouin

/ones, the angle ф governing the proportion ol the two

polari/alion components of the acoustic branch was

determined. L'ig. le. together with the rotation sense - being

positive for the acoustic branch. For the optic one the

polari/alion angle is я/2-О and the rotation sense negative.

Once the polari/ation components are resolved, it is

straightforward - using the quantum-mechanical branch

crossing formalism - to extract the frequencies of the unper-

turbed LA and TOI branches, displayed by dolled lines in

l-'ig. la. as well as the off-diagonal interaction term Л.

l-'ig. Id. responsible for the coupling. In this way the 2x2

dynamical matrix providing complete description of the

dynamics of (he two branches is fully reconstructed from the

experimental data. Full lines in l-'ig. la-d represent results of

the (i/i initia quantum mechanical calculations of the latlice

dynamics of silicon which find in the present results -

comprising also frequencies and eigenvectors ii, the other

high symmetry directions - an excellent experimental

confirmation.

Measurement of phonon dispersion curves in Cr->O

The study of СгЛЬ, |.Ч|. having rhonihohedral symmetry,

was undertaken to follow up the investigation of the ionicily

and the polarisahilily of the oxygen ion. which was started

by measuring phonon dispersion curves up lo the highest

frequencies of about 40 Til/ in quail/ (SiO->) and in sapphire

(AI :O,). The crystal of Cr : O, with a volume of about 4 cnr

was examined on the PRISMA tinie-ol'-flighl spectrometer

at ISIS (with a limited success) and in March 1У93 on the

triple axis spectrometer TAS-1 at the JRR-3 reactor at

JAHRI.

D F(440)

О F|006)

О 0.2 0.4 0.6 0.8 1

l-'iif. I: l'honon ili\i>ertion relations loi' llie Xy brunches (ilimR11 III/ in \ilieon lti>: ineltislic \lrnetnre faetim for the iieon.\ticphonons observed in ihc 440 ami 'W> Hri/loiiin :<>ne.\ (h).IKiliiri-iiinin чнк/е in ilic 1110) i>/in/i' le) and the correspondinginteraction lerin of'lfie ilviitniiieii/ inufrh (ill. Tile solid г и т л arebused un results of the tib hiiliit ('(tlcnhilions.

The investigations were concentrated on thedirection. The thriv lowest modes out of each of the five"even longitudinal" ones and the five "odd longitudinal"ones were measured and identified, us well as the two lowestdouble degenerate "transverse" modes. Three more of the"transverse" modes were measured and could be identifiedby calculations of their frequencies and intensities fiom alattice dynamical model. The shell model calculations with9 parameters reproduce the data satisfactorily well. Studiesof other symmetry directions, requiring an extended energytransfer range, are waiting tor the IN I spectrometer after therestart of the ILL reactor.

Incommensurate and ferroelectric phase transitionsin .Sn2P,Sef,

The dynamical behaviour of the semiconductingcompounds SiiiPiSj, and SibPiSCf, has been recentlyinvestigated by optical spectroscopy. While the firstcompound exhibits a direct paraeleclric to ferroelectricsecond-order phase transition at 340 K. in the isonw.phousSe-based compound, the same type of structural changetakes place in two steps: a second-order transition fromparaelectrie to a long-wavelength dipolar-modulated phaseat Tj=220 K. followed by a first-order "lock-in" transitionto the homogeneous ferroelectric state, at Tc=193 K. Thesetwo compounds, as well as their solid solutionsSii2Pi(Se4S|_x)(r are used in non-linear ultrasonic devicesbecause of their strong pie/.oelectric properties.

From a more fundamental point of view, the x-T phasediagram of the mixed compounds exhibits a rather rare kindof high-order critical point, the so-called Lifshit/ point(X|=0.28; Tj =295 K). For x<xf, a direct paraelectric-Io-lerroelectric second order phase transition is observed, whilefor x>X| . as in SiiiPiSefi, the intermediate modulated phaseis stable over a finite temperature interval ДТ(х) = T,(x)-Tc(x).As x—>X|/*", both the stability range ДТ(х) of (he modulatedphase and the modulation wave vector for Tc(x) < Т < Tj(x)vanish continuously. The crit'cal behaviour associated withLifshil/ points has been studied so far in nemaliclerroelectric liquid crystals and in helimagnets such as MnP.

The first inelastic neutron scattering data | 4 | wereobtained with a I cm' single crystal of SiiiPiSe().The experiment was carried out on the TAS I thermal-beam3-axis spectrometer at the JRR-3 icactor at JACRI.Preliminary elastic measurements to determine the positionof the satellite reflections in the modulated state (TC<T<T,)confirmed previous X-ray data. The polarization of themodulated ionic displacements is found to be directed alongthe a-axis of the pseudo-orthorhombic cell (a = 9.652 A.b = 7.679 А, с = 6.810 A: (X = 90°, P = 91.4°. у = 90°). i.e.transverse to the modulation wave vector qs = 0.085c* and0.1 c* at 193 К and 214 K, respectively.

COLLEGE 4

Hence, in the paraelectrie phase, one expects to observethe mixing of a soft transverse polar optie mode (TO-mode).propagating along c* and polari/.ed along a, with an acoustic(ТА) branch of same polari/ation. Fig. 2 shows the inelasticresponse at (4.0.-Ç). Гог ъ = 0.2, 0.3 and 0.4. The upperfrequency peak (near 3.5 ineV l'or Ç = 0.3) corresponds tothe TA mode, while the low frequency tail (from 2 to 3 meVfor Ç = 0.3) was tentatively identified with the TO moderesponse. This tail gradually disappears on cooling, as seenin Fig. 3, until, below Te. = l°3 K, a normal (i.e.symmetrical) ТА response is recovered. This behavioursuggesls that the tail arises mostly from а ТА-ТОinterférence effect, as opposed to a true one-phononresponse. It is hoped that further mea.tinVmenls of thecoupled-mode response as a function of tempera I lire,in selected Brillouin /ones, will enable one to extractthe independent TA and TO mode-parameters.

Magnetic excitations in CsFeClj in a magnetic fieldperpendicular to the c-axis

In CsFeCI} the Fe~+-ion with effective spin one haslocally a singlet ground state (m = 0). The ferromagneticinteractions along the c-direction and the antiferromagneticinteractions perpendicular to it are loo weak as compared tothe anisotropy to introduce long-range order in the absenceof an external field. The excitation spectrum wasinvestigated at LLB by inelastic neutron scattering in anexternal magnetic field up to 6 T. applied perpendicularly tothe c-axis |5| . It was found that, with increasing magneticfield, the whole dispersion sheet is shifted towards higherfrequencies and a splitting appears. A local Hamiltonianwhich neglects exchange interactions between all neighbourscan give a qualitative explanation of the intensity of themagnetic excitations in dependence of the magnetic field.A more sophisticated theory. RPA-diagonalisation of the

/•"r.i;. 2: Mt\etl ТЛ-'IO line

„I Q = 14. (I. - c/

-4 -3 - 2 - 1 0 1energy transfer (meV)

re ill .1(111 К in .ViM/MVv,

сЁсо

сои

T=300K

• T=214K

- - - - T = 1 8 2 K

*«*-6 -5 -4 - 3 - 2 - 1 0 1 2

energy transfer (meV)

/•'/К. .>'.' Тснцч'пншч' (li'i>i'iitli'iiw iif iiii,\eil ТА-ТО п'.ч/in .V/b/4V<v, at Q = 14, 0. - tt.?/.

Heisenberg Humilloniun used to describe ihe magneticbehaviour of CsFeCI}, yields - apart from a mismatch for themodes at high energy transfers - a satisfactory descriptionof the magnetic excitations of CsFeCI^ in dependenceon the magnetic field as displayed in Fig. 4.

II) Hcisenberg antiferromagnets with half-integer spin -universal properties?

Inelastic neutron scattering at ILL in the ID phase on thespin -S'=3/2 Heisenberg chain AgCrPiSj, indicated a spin-wave velocity С ~ 4.6./, well in excess of the classical value2./.S' = 3./. This result emphasix.es the strong quantumcharacter of the 5=3/2 Heisenberg chain and the similaritywith the S=\'1 system that has a gapless excitation spectrumwith a spin-wave velocity С = nJ/2. '.e. я/2 times thecorresponding classical value. Universal properties areexpected for the half-integer systems, but il is notimmediately evident that the relevant quantum effects aremeasurable for spins larger than 1/2. The universalbehaviour could be checked via the relation between /егоtemperature susceptibilities and spin-wave velocities, it isexpected that #7=0) = 1/(2лО valid for spin .S'=l/2 holdsalso for oilier half-integer spins. Al present, for .V = 3/2. thisrelation can be examined only by extrapolation as depictedin the f:ig. 5 that displays the existing calculatedsusceptibilities together with the experimental points |6 | .While the /его temperature susceptibility cannot bemeasured (the weak 3D interaction induces order) and hasnot been calculated, the extrapolation of the temperaturedependence agrees with the value obtained using themeasured spin-wave velocity. This result is compatible withthe theoretical predictions that suggest universal criticalproperties for half-integer >pins.

C O i L EG E 4

Finite si/o effects in two-dimensional magnets

Whilst most crystals studied at ILL contain about l()-4

atoms, the statistical mechanics which is used to calculatetheir behaviour is only exact!}1 correct for a hypotheticalsystem containing an infinite number of particles. Usuallyone needs not worry about the fact that real systems arefinite, since N = K)-"1 is a \ery large number, and Imite-si/ecorrections to the statistical mechanics of the infinite systemare generally negligible. Theoretical work at ILL and theE.N.S. in Lyon |7 | , has stressed that for two-dimensionalsystems this is generally not true, and one must always takefinite-si/e effects into account. The essential reason for thisis that in two dimensions properties depend upon log(N)rather than N. Coupled to the obvious fact that macroscopictwo dimensional systems only contain some ( К)-4)-'-' = К)"'particles, one can see that log(N) cannot necessarily betreated as an almost-infinite number.

A spectacular example of the breakdown of theapplicability of the "Ihermodynamic limit" (i.e. theapproximation N = °°) is seen in the behaviour of magnetswhich approximate the two dimensional XY model: in otherwords layered magnets or ultra thin films with easy-planeanisotropy. In the case of layered magnets, it can be shownthat weak interlayer coupling determines an effective finitesi/e. which is smaller than the actual sample si/e.

Recent work | 7 | has re-examined inelastic neutronscattering data for the layered easy-plane ferromagnetRb2CrClj measured on 1NI2 in the 1980's [8]. This materialis expected to show a Kosterlit/-Thouless phase transition,where the impairing of defects in the ferromagnetic spinstructure causes a coll. pse. with increasing temperature, ofthe effective spin wave stiffness Кс(1. In the infinite systemthe collapse is sudden and is known as the "universal jump".

A theory which lakes into account finite si/e effects predictsthat the universal jump is severely rounded. The theory canbe rigorously tested because it predicts that KL.t| can bederived equivalenllv from neutron diffraction measurementsof the spontaneous magneti/ation (itself a finite-si/e effect),and from the weak-field bulk magneti/ation. as well as moredirectly from inelastic neutron scattering measurements ofthe spin wave frequencies.

S-D 0.1

_,«•-•-§-*._•~ ~ - -

Xo=l/(2*C)

reduced temperature, k T/J

/•7.4. 5: 77ic \usceptihility oj the </ii<i.\i-ll) aiili/rmiiniigiielЛцСгР-Sf, in reduced units %1/(1>\1ц)~. The open circles representthe i/iuinlttin Monte-Carlo simulation Jor ,V=.i'/? />vSuiuMk&Ktirkijtin'i (l'/i\'.s. Ki'v. H. IWI), while full circlesreproduce the measured temperature dependence scaled In theexchange constant ,1 Л/(= l(K> A', ami the ;ero temperature mineIX) is calculated using the measured spin-wave velocil\ С = 4M.

Ф 6 Т mode 1 jО 6 Т mode 2 -

0.7 0.8[4я/а]

0.4 0.6С [27Г/С]

/•7.1,'. 4: Magnetic excitations in C'sAcCVj at l.fi К for three different \\mmelr\ directions: the donhl\ degenerate mode at :ero field (.)and the imnle\ separated at a field oj f> Tesla perpendicular to the c-n\i\ fAVW/w/\ » anil Ql. The full Hne~, are calculated from a HeisenhergHuinillnnian in RI'A theory. The dashed line indicates the middle between the -его fieltl /re</iiencie\ and the upper mode at 6 Tesla.

COLLEGE 4

Fig. (1 compares l\,|| lor КгьСгС1!.) determined In thesethree techniques. Tlio temperature scale is norma'i/ed In atemperature Т ц; | which is I ho transition temperature of thehypothetical infinite system. The figure also plots the slopeol the curve calculated by ix'iuiniiali/alion group theory al aU1 mpcratuix- Т \ just above ï \ | which is a specialtemperature lor the I'inite system. Given the diversity oftechniques involved. Ihe agreement between the theoreticalprediction and the three experimental curves is impressive,clearly demonstrating the occurrence of a ilet'ecl-unpairingtransition in Rbi(.'r('l.|.

Influence of dilution on the static critical behaviourol'.M)-Heisenher;> reentrant compounds

l'iuler a random dilution of their magnetic atoms, someIrusiraled magnetic systems develop a peculiar behaviourknown as reentrance: when decreasing Ihe temperature fromthe paramagnetic stale, thev first undergo, at T r . a transitiontowards an ordered mag:.otic phase: then, al a lowertemperature, strong irreversihilities appear, characleri/ingthe onset of a spin glass like phase.

An experimental study of Ihe influence of dilution on thestatic critical behaviour has been performed at 1.1.H in theinsulating frustrated system C'dC'r-i, ].s,ln-«4S4, based on the31)-lleisenherg ferromagnci СЧЮ'т.Чд |9|. Unusually highvalues of the cr i t ica l exponents j and v (2 and I.respectively ) have been determined for the x=().()5 reentrantcompound by means of SANS measurements above T(-.Such behaviour is illustrated by Fig. 7 which presents theobserved correlation lengths. In ihc absence of frustration,such results arc theoretically expected in the limiting caseclose to the geometrical percolation threshold. Surprisingly,diffraction experiments done in the ferromagnetic phase ledto the ЗП-Heisenberg v alue for the critical exponent (5.

One of the effects of frustration thus appears to be anenhancement of the disorder introduced by dilution, 'eudiiigto the limiting values y=2 and v=l for a weak 5'/< dilution.

Although it has not been observed, the existence of anasymptotic pure behaviour for small positive reducedtemperatures is strongly suggested by the combined resultsobtained above and below T(-, Л highly interesting point isthe very probable absence of crossover in the ferromagneticphase, w hich means two different bcha\ jours on each side ofthe transition. This is aliribuled to the presence of a longrange order, inducing а поп /его local mean magnetic field.The expected influence of such a field is to reduce theeffect' of disorder, which appears to prevent the systemfrom developing a dilution induced static critical regime.

Secretary: Jiri Kulila

Rol'ci't'iK'cs

( 1 1 I'. Oianiuwi. S. (Jironcoli. P. l'avoue and S. Haroni.Plus. Rev. В 43. 72.} I ( I W l ): IX Sirauch. P. Pavone.private communication.

|2| .1. Kulda. I). Strauch. Y. Ishii. S. Kalano.to be published.Th. May. B, Dorncr. I I . Schober. 1). Strauch.U. Steigenherger anil Y. Morii, to he published.

R. C'urrat. Yu.M. Vysochanskii. and S. Kalano,to he published.

B. Schmid. B. Dorner. D. Pelitgrand. 1..P. Regnaultand M. Sleiner. /..Phys.B - Condensed Matter.submitted.

I I . Mulka. C". Payen and P. Molinié. Hurophys.

| 8 ||Ч |

S.T. Bramwcll and P.C.W. Holdsworlh..1. Appl. Phys.. in press.

M.T. Hutchings et al. J.M.M.M. 54-57. 673 (1980).S. Pouget. M. Alba and M. Nogues. Proceedingsof МММ'ЧЯ. to be published: S. Pouget. Thesis.INSA Toulouse and ILL.

0.00.8

theoreticalslope at T*

Rb2 CrCI4

TKT = 43.3 К

0.9 1.0ТЯ.„

1.1 1.2

/•/';'. ft: S/nu iriM>' \uttnc\i i>tinii>H'lci Kltliiifii\iiri'il h\ incla\tn

Ш'ппон w ullft'iiii; ti in /rsj. i nHijttin'tl In I In II tlcrirt'il Irtiiit

4><>iiiii>iroii\ »i4vnt4i:<iii<n} liln\lifil liiifi. hulk imi\incti;4lii»<

t \4iiurr\l. anil lilt' llii-di'cin til /tri'dii'limi.

100.01 0.1

I-it!. 7: Infhu'itn' <>/ dilution in CdCr->(} ^/»>VV^ on ih< criticalhchtivitmr of ilic < iuri'luiitw Iciigili. ahovc T(-. The ( riiictil сл/ïfw»'///v. nhfdincd (пил tlit' \l<tfjf of ihc \ir<tight ///J<'.s, /\ iiici'('tt,\ct/h\ (И\1>п/(Т Iгот 0.70 in l/ic pure ctisc ft> 1.0 forx = 0,05,

C O I i E G E 4

The y => a phase transition in Ce

Amir P. Murani

The y =» a phase transition in cerium metal lias beenthe subject of a large number of investigations. Thefee y-Ce stable at room temperature shows normalCurie-Weiss magnetic susceptibility. On application ofpressure ( > 6 knar) or on cooling (below 110 K), itsvolume contracts abruptly by ~ 14 % maintaining thesame fee structure 111. The transition to the new phase,called rx-Ce, is accompanied by a marked drop in themagnetic susceptibility which now shows enhanced Pauliparamagnelism |2.3] characteristic of non-magneticsystems which do not posses well defined localmoments.

The first theories of the y => О- transition associated itwith transfer of the locali/ed (magnetic) 4f electron tothe conduction bands. Certain experiments |4], however,showed that the valence did not alter significantly at thetransition, and triggered new ideas based on the Motttransition model (localized 4f electron in y-Ce =>delocalized 4f band in a-Ce) |5]. Other theories, basedon the Kondo-lattice |6 | and Anderson impurity models[7| have put forward the idea of the Kondo volumecollapse due to increased hybridization of the localisedf-electron with the conduction electrons in the a phase.

We have performed a neutron inelastic scatteringinvestigation of the temperature induced y => a phasetransition in Ce, which we believe could aid our choiceof the most appropriate model to describe the phasetransition. The measurements on the НЕТ time-of-flightspectrometer at ISIS were, in fact, performed on Cealloyed with 7 at. % Sc which stabilizes the fee phaseagainst (dhcp) p-Ce formation. Gschneidner et al. [ 11have reported that addition of about 7 at. % Scsuppresses formation of (3-Ce almost completely (< I %)and (unlike Th or other additives) addition of up to10 at. % Sc has negligible effect on the volume changeAV/V at the transition compared with that for pure Ce [ 1 ].

The y => a transition is of first order and showssignificant hysteresis. On cooling the transition occursat - 1 10 К while the reverse transition is observedat ~ 170 К on warming 11,2|. We have made use of thehysteresis to carry out measurements on the two phasesat the same température, (viz. 125 K), first performingmeasurements in the y-phase at 125 К then cooling thesample to 20 К (a-phase) and finally warming up againto 125 К (a-phase) where measurements were repeatedunder identical conditions. A one to one subtractionbetween the two data sets eliminates all possible non-magnetic contributions due to phonons, multiphonons aswell as traces of hydrogen. The difference in the phononspectra between the two phases is small compared with

the resolution. The resultant difference signal measuredwith neutrons of incident energy 2100 meV (the highestenergy currently practicable on the НЕТ) using twodifferent energy resolutions is shown in Fig. 1 where thepositive intensity structure is predominantly the y-phaseresponse while the extended "negative intensity" tail ismainly the a-phase signal. In the diagram the continuouscurve represents the higher statistical accuracy (poorerresolution) data corrected for the Ce''"1" form-factorvanation.

-0.2'-500 0 500 1000 1500 2000

energy transfer jmeV]

Fig. I: Spectral intensity difference between yaml a-Ce at125 К measured using neutrons of incident energy 2100 meVwith two different energy resolutions. The continuous curveshows lite low resolution (higher statistical accuracy} datacorrected for variation of intensity with 0} (hence Q) for fixedscattering angle <2в>, assuming the Ce** form factordependence.

If we assume the modified sum rule /S(Q,ci))dco «HQ- = n()~F"(Q)<nf> to be valid, where <ii|> is the 41"occupancy, then numerical integration of the form-factorcorrected data (shown in Fig. 1) up to 1500 meV yieldsthe change in the 4f occupancy at the transition Д<п(> of0.2 ±0.1. Furthermore, if we assume <iif> = 1 for y-Ce,we obtain <nr> = 0.8 + 0.1 for a-Ce, consistent withpositron annihilation |4] and Compton scattering [8| datawhich indicate close to fully trivalent state (occupancy ~l)even in the a-phase. The latter measurements, however,did not distinguish between localized and band-like 4fstates while, as discussed below, the present neutron datasuggest that ~ 0.8 electrons remain localized in a-Ce.

Low temperature (20 K) magnetic scattering in a-Ce(obtained taking La as the non-magnetic reference) usingneutrons of incident energy 600 meV is presented

COLLEGE 4

in Fig. 2 in the form x"(<»)/co, where the continuous andthe dashed curves show the best fits to the Lorent/.ianand the Kuramoto-Miiller Hartmann (KMH) spectralfunctions 19) yielding u)0 ~ 170 and 156 meV. respectively.The other parameter of the KMH fit a (= n<nf>/N), foundto be 0.43 ± 0.03, yields the occupancy <nr> = 0.83(assuming the degeneracy N=6), in good accord with theresult obtained from the integrated spectral intensity.

0 50 100 150 200 250 300 350400energy transfer (meV)

Fig. 2: Low temperature (20 K) dynamic susceptibilityresponse oftt-Ce represented as %"(0))/(Л The continuouscurve represents the LorenKian spectral fit anil the dashedcurve shows the fit to the Kuramoio-MUlter Hartmann function/9/. C r i + form-factor variation lias been included in the fits.

It is interesting that the Kondo temperature T0 (TK)for a-Ce obtained from our neutron data is fairly close tothat predicted from the linear specific heat coefficient yvia the Fermi liquid relation [10] y = П~Ьъ~<П(>/3<а„,where (00 = T 0 (T K ) . With co0 = 170 ± 10 meV and<nr> = 0.8 ±0.1 we obtain 7= 10.5 ± 1.5 mJ mole"1 K'2,in reasonable accord with 12.8 mJ mole Ю~, obtainedfrom specific heat measurements [3|, allowing for some(s, p, d) conduction electron contribution. A similarevaluation for the susceptibility from the relationX(o) = H2<n f>/3co0, yields x(o) = (3.1 ± 0.4) x10"4 emu mole"'. This is slightly smaller than the bulkvalue of 5.32 x 10"4 emu mole"1 at 50 К but thediscrepancy, we believe, can be understood.

The у minus a difference signals measured with450 and 2100 meV neutrons have been analyzedassuming a narrow quasi-elastic response for y-Ce. orbroadened crystal Field states, Г7 and Г8, giving rise to aquasi-elastic and an inelastic component. For the a phasewe have assumed a broad inelastic Lorentzian spectralresponse (c.f. Fig. 2). We have also included form-factor

variation of intensity with energy transfer со (and henceQ) with the fitted functions. For y-Ce the singlecomponent quasi-clastic fit yields a width of7.5 + 0.5 meV while the two component crystal field fityields a quasi-elastic width of 5.5 ± 0.5 meV (at 125 K).In Fig. 3 the thick continuous curve (and the short dashedcurve) represents the overall best fit to the 450 meV data.The residue in the region of ~ 260 meV represents thespin-orbit excitation. This is shown in the inset togetherwith the curve (dashed) which parametrix.es thespin-orbit excitation (width 40 ± 5 meV, position260 ± 10 meV) taking into account the S-O excitationin a-Ce (see below) and the appropriate form factor forthe "Fiyi => ~F-i/2 transition [ 11J.

-100 0 100 200 300energy transfer (meV)

Fig. J: Two component leust-sauares fit to the y—tt differencesignal (E; = 450meV). The continuous and short dashedcurves represent the Ce' + form- factor corrected overall jit.The residue is plotted on an expanded vertical scale in the insetwhere the Ions dashed cunv parametrici'es the S-O excitation,taking into account the "Ay; =* ~F^ structure factor 111 ]as well as the S-O excitation in a-Ce.

The data for E| = 2100 meV presented above in Fig. 1are reproduced in Fig, 4 together with the resulting fits.The continuous curve represents the overall fit obtainedfor the same parameters as for the 450 meV data.Only the vertical scale is adjusted by 12 % between thetwo data sets which can be accounted for by possiblesystematic errors in the vanadium calibration anduncertainty in the scattering angle (± 0.5 at 4.5 ).The dashed and dash-dotted curves represent the ground(2F5/2) state components for the y- and oc-phases. Theresidual intensity is shown on an expanded vertical scalein the inset together with the curve obtained for the same

COLLEGE 4

parameters (components are shown dashed) as used to fitthe S-O region in the lower energy data, Fig. 3.We believe the peak at - 450 meV represents the S-Oexcitation in the a-phase, although its relatively highenergy as well as broad width (- 100 meV) may appearrather unusual. It is emphasized that the S-O excitationevidenced in a-Ce is not an artifact of the fit or the fittedspectral forms, although its exact position, shape andwidth may depend on the spectral functions (Lorentzianor KMH) chosen to represent the ground state response.In fact, the S-O excitation is clearly observable in the asmeasured difference signal in Fig. 1. particularly in theform factor corrected data (continuous curve). Itsrelatively small intensity compared with the mainresponse is in good quantitative accord with theory,taking into account the respective form factors [II].

These results together with the observed magnitudesof the characteristic (Kondo) energies of a-Ce(TK ~ 2000 K) and y-Ce (TK ~ 100 K) provide strongsupport to the "Kondo volume collapse" theories of they=> a transition [12|.

Acknowledgements

It is a pleasure to acknowledge the collaboration andassistance of Z.A. Bowden, A.D. Taylor, R. Osborn andW.G. Marshall, as well as many other members of staffat ISIS. Helpful discussions with B.R. Coles, B. Coqblin,S.W. Lovesey, C. Lacroix, M. Lavagna, К. Matho, andD. Nunez-Regueiro are also acknowledged. Thanks arealso due to R. Raphcl and B. Gorges for their assistancewith the sample preparation work carried out atthe C.N.R.S.. Laboratoire Louis Néel, Grenoble.

•500 0 500 1000 1500 2000energy transfer (meV)

Fig. 4: Model fit u> the y — a difference intensity forE, = 2100 meV (for the same parameters as the 450 meV data,see text). The two components of the fit are shown by thedashed ly-Ce) and the dash-dotted (a-Ce) curves. The residueis shown on an expanded vertical scale in the inset, togetherwith a fit assuming S-O excitations in both phases,shown b\ the dashed curves.

In conclusion, we have identified a single ion spectralresponse in a-Ce, well described by the KMH spectralfunction (TK ~ 1800 K) or an inelastic Lorentzian(TK - 2000 K). Numerical integration of the differencesignal between y and a-Ce measured with high energyneutrons at the same temperature and over the sameQ-range thus suggests that the 4f electron remainslocalized in a-Ce to the extent of around 8 parts in 10.Further evidence for localized 4f states in ot-Ce isprovided by the observation of broad yet well definedhigher-lying spin-orbit excitation at finite Q ' s .

References

[ 1 ] K.A. Gschneidner Jr., R.O. Elliottand R.R. McDonald, J. Phys. Chem. Solids 23,

1191 (1962).

[2| J.M. Lawrence and R.D. Parks, J. Physique 37,

C4 249 (1976).

[31 D.C. Koskimaki and K.A. Gschneider Jr.,Phys. Rev. В 11,4463(1975).

[4] D.R. Gustafson, J.D. McNutt and L.O. Roelling,Phys. Rev. 183,435(1969).

[5] B. Johansson, Phil. Mag. 30, 469 (1974).

[6j M. Lavagna, C. Lacroix and M. Cyrot, Phys.Lett. 90 A, 210 (1982): and J. Phys. F. 13,

1007(1983).

[7] J.W. Allen and R.M. Martin,Phys. Rev. Lett. 49, 1106(1982).

[8] U. Kornstadt, R. Laser and B. Lengeler,Phys. Rev. В 21, 1898(1980).

|9] Y. Kuramoto and E. Millier-Hartmann,J. Magn. Magn. Mater. 52. 122 (1985).

|IO| T.V. Ramakrishnan and K. Sur.Phys. Rev. В 26, 1798(1982).

111 ] E. Balcar, and S.W. Lovesey, J. Phys. С 19,4605(1986).

[12] A.P. Murani, Z.A. Bowden, A.D. Taylor,R. Osborn and W.G. Marshall, Phys. Rev. В 48.13981(1993).

COLLEGE 5

Crystal and MagneticStructures

Members of the college

Internal Members

T. Baumhach

S. BramwellP.J. BrownT. ChaitopadhvayP. Convert.I.A. DeCarvalhoPaixàoЛ. FilholE. Garcia-Maires v Cortes

B. llainclinA.\V. Hew atK. Hinrichs

(). Isliard

.1. KuldaG. LauiensclilagerM.S. LehmannA. MagerlS.A. Mason

External Members

M. Anne (CNRS)R. Arons(CENG)M. Bacmann(CNRS).1. BarucheKKSRF)E.F. BL-riaui(CNRS)M. Bonnet (CHNCi)J.X. Boucherie (CENG)C. Cohen-Aildad (IBS)A. Filch (ESRF)13. Frucliari (CNRS)I). Gi\oixl(CNRS)C. Janol (ШЕ)

Introduction

Ci.J. MclnlvreA.P. MuraniH. Murphy'/.. MursieM. Nuileyli. Ouladdiaf.1. Panne/tierM. ReehuisC. KillerV. Rodrigue/.1. Rodrigue/-Carvajal(). ScharpfF. TassetP. TimminsT. VogtC. WilsonC. /even

A. Kviek(ESRF)M. Mare/io(CNRS)J.C. Mamieggi(CNRS)E. Pebav-Peyroiila(IBS)M. Schlenker(CNRS)J.Schwei/erlCENG)J.L. Soubeyroux(CNRS)E. Ressouche(CFNG)C. Ricke! (ESRF)C. Veltier(ESRF)C. Wilkinson (EMBL)G. XaccaillBS)

Life in College 5. already disrupted by the reactorrefurbishment, was further perturbed by the reorgani/alionof the ILL in 1993. .Several of our members now occupymore managerial positions: Jane Brown is now Head of theScientific Computing Group. Alan Hewat is Manager of theDiffraction Group, and Claude /eyen is Head of theInstrument Development Branch. Most members of theDiffraction Group also spent several weeks shilling to ILL4.This move puts most members of College 5 in much closerproximity than before which should be beneficial toicientific activity in the long term.

In spite of these changes, scientific activity within theCollege has continued apace both at home and abroad. ThreeCollege members continued detachments to other neutronscattering facilities in 1993: Manfred Reehuis to the Hahn-

Meilner Insiimi to help to bring on-line (he four-circledil'fraclomeler and to introduce ihe Berliners to the 1)15position-sensitise detector on loan during the shutdown.Juan Rodriguc/-Car\ajal to Laboratoire Léon Brillouin. inpart lii he responsible for the I) IЛ powder diffractomeleralso on loan, and Thomas Vogt to Brookhaven NationalLaboraiorv to help construct a new powder diffractometerand develop novel monochromators of sandwichedgermanium. Closer to home Jean Pannetier spent the majorpart of the vear doing industrial research in the Groupelincstigalions Slruclurale at I he Centre de Recherche deVoreppeof the Pechmcv company.

In similar \ein several College members look theopportunity of (he shutdown to make shorter extended visitsto other facilities: Sieve Braimvell to TRIl'MF in Vancouverwhere he was involved in |.|SR experiments ami intheoretical studies of frustrated magnets: .lane Broun i<>Coimbra. Portugal, as Visiting Giilbenkian Prol'essoi in thePhysics Department and (hen on 10 Brookhaven NationalLaboratory to work wilh Gen Sliiranc on magnetic inelasticscaltering from ferromagnetic compounds showingquadrupolar interactions: Garry Melntyre ID Lucas Heightsin Australia lo assist in the experimental program on theГонг-circle dilTraclomclers and to demonstrate the benefits ofposition-sensitive deiectors: Claude /even lo the ISSP toadvise in the construction of the Ihree-axis spin-echospectrometer PONTA and to JAHRI to use the three-axisspectrometer TAS-1 and the precise neutron optics machinePNO. Most College members have also done experiments atvarious neutron and x-ray centres in Europe and furtherafield, and have always been warmly welcomed. These \ isiboften reveal elegant solutions to experimental problemsabout which we. with ihe luxurv of 'high flux', have milworried. Being the reversal of the usual scientific tourismthey also establish new and different contacts and fostergoodwill for the future experimental program at the ILL.

The past year has also seen the departure of most of dieremaining thesis students: José De Carvalho Paixào. KlausHinrichs. Olivier Isnard. Gerd Lautenschlager. HelenMurphy and /.опт Mursic. Mark Nutley will finish at theend of 1993. leaving only Claire Wilson who is due to departjust as the next batch of students arrives in the autumn of1994. Many of these students have been forced by thereactor shutdown to perform all of their experimental workelsewhere, and to spend the resl of the time at the ILL inrelative isolation compared to their peers at the homeuniversities. Rather than demorali/c. as might be expected,this preniaiure introduction lo 'suitcase" science has butstrengthened their ability lo work independently and to adaptquickly lo new experimental situations. Not that this is ascenario that we would recommend for future students!

In addition to the contributions both to ihe organi/alionand to the content of the Workshop on Magnetism and theIAEA Materials-Research Workshop described in detailbelow, several College members assisted in planning thescientific programs of microsymposia of the 16th lUCr

COLLEGE 5

congress in Uciiing ,iml associated satellite meetings held inAugust and September of I'W.v As in previous vcars severalmembers ol ilic College helped organi/c or Iccuncd .И theanimal HI-.K(4 I.I-.S (Higher huropean Research Course loil'scrs ol Large Lxpenmcnlal Sv stems i course lor voungscientists held in thé spnng-lime. Л fine three-volume soi ollecture noies, edited bv .1. Baruehel. J.I.. Iloilcau. M.S.l.ehinann. .l.R. Reynard and С. Schlenker. has rccenllv beenpublished In Les l-.ditions de Plnsk|iic ami Springer-Ycrlag.

\\'ilh a lillle help from oilier niemhers of [he College.Alain l-ilhol has produced .in Lnglish \ersion of "Video II.I.Interactive". Macintosh sol и\ иге \\hich presents thescientific activities ol the II.I. in the form ol interactiveanimation and simulation ol various tvpicul experimentsThe original l-'rench version was produced lor thetechnology exposition held annuallv in (irenoblc. и here Hhas alvvavs been vcrv well received In scientists and lavmcnalike, and the new Lnglish version was similarly verv muchappreciated In participant-, m ihe IAI-.A \\orkshop. Thistvpe of puhlicitv has immediate visual impact, and uiihfurther support should be made more vvulelv available.

Amidst much globetrotting in search ol beam-lime andconference interaction, scienlilic aclivnv at ihe II.1. has oftenconceniraled on analvsis ol ihe remaining (.lifficull problemsof experiments done the \ears helr-e ihe sbuldown. \\hatthe scientific hiiihlighls ol IW.} lack in numbers tbev morethan compensate in depth and diversiu '

Scientific Highlights in 1993

Crystallography

The parai'lfdric and iVrnii'lvctric phasesoi'hetaint' phosphite

During ihe last decade orienlational glasses haveattracted considerable attention. These compounds exhibil atransition Iront a crvslalline high-lemperature phase to aglassv low-temperature state, which is characleri/ed In acolleclive tree/ing ol reonenling moments in anorientation.ill\ disoideied phase 'I'he besi-know n examples arealkali liai tile - .11 kali cvamdc mi Mures, such as I KHri| v ( K ( ' \ l v .and solid solutions of l'bll :P()4 and I Nil ,)II :P(),.

RecentK new svsienis ol this i\pe have been discovered.namcK. mixed crvslals ol ferroelectric betaine phosphaie.(CIl i l jNCMiCOO.HïPO, (HP), and ferroelectric bêlantearseiiale. (Cl l ; I ,N'CH :C()().H (As()4 I li A I. and mixedcrvslals of HP. ami antilerroelectric belaine phosphite.((TI-JiNCH.COO.IhPO. i l iPl i . both ol which, accordingto dielectric ami specilic-heal measurements, exhibit аIruslralcd polar stale over a wide concentration range Thesecompounds adopt hulrogen-honded structures, where (heIndrogen bonds ordet along linear chains while the weakinteractions across the chains determine whether the orderedslate is ferroelectric or aiililerroeleclric. Onh limitedstructural information is available, even lor Ihe purecompounds.

\l ihe instigation ol phvsicisis at the I'mveisiiv olDurnisiadi. a program ol investigation ol the structuralproperties nl these glasses was begun |iist bel ore the icaclorshutdow i. beginning with determination ol the siiucluie olpure Ki'l in its d i l le ienl phases l-rom ilieleclricmeasurements n is known to undeigo a transition to alerroeleclric -luk1 at 2Id K. and possiblv another transition al177 K. In Ihe lirsl expenment the structure ol HPI wastherefore investigaied at 245 K. 140 К and III К In smgle-crvsi.il dillraction on Did 11.2|

I he sinicture determined in llns expeiiinenl loi theparaeleclric phase is shown in I'ig. I. This phase ol BPIbelongs to space group P2|/c w nh two hall-occupied sitesrelated bv inversion (.entres lor both I l i l ' i and IIM5iI I'ig. 21. ( )rdering ol one or both ol these protons In remov alol the inversion centre will give a lerroeleclric structure wilhthe same unit cell as al room temperature bin with the lowersvnimelrv ol P2|. In going Iront P2|/c to P2| the relleclioneoiulitioii. hdl. I = 2n, is removed bin the additionalreflections inav be verv weak il ihe 5(1 remaining atoms inthe new asvmmclric unit are sti l l verv nearlvcentrosv innieli icallv related. Tins was indeed Ihe case, but

/ /',' / ///( <m тип n ft nun ol hcltiuit f>lio\[>hiit <// -l^ A

in llir/IIIKH In nit />liii\i ln~.il.llh n \;ii>ii\ iit-tir III /2i iiiiil Hi I4i

in hrluiiK />liii\iili(iii iiiii/hflniiK (ii \fiinli

I IV -' \lhl-llllllll illllHIIH! Ill llll1 I llllllllllV III l/ll' /Ч-llllllf Illlll

'ili i'I tin pinncli< lin />lni\r n/ htiniiH' nliii\i>hiir

COLLEGE 5

the hOI. I * Un. reflections were clearlv visible at ho I h IVOK;nul H)K. The' siruelure refinements showed ordering ol bol hIII l.i) ami 11(15) ni both temperatures, in the chemicallymore plausible arrangement ol' two icrvstallographicallyindependent) H-.PO; groups rallier than one HP()( group anilone H ; PO ; group.

Ordering of Ihe hydrogens alone did not howeverentirely explain the diffraction iniensilies in Ihe ferroelectricphase: as expected from the observed ferroclecineitv the res!of the s i r i i c l u r e a l so h e c o m e s ' s i g n i f i c a n t l y 'noncentrosymmelnc. with the atoms of Ihe phosphite groupshowing the largest degree of noncentrosy mmetry al boththe lower temperatures, Furthermore the bridging hydrogenatoms appear to he fully ordered at 140 K. yet the markedaverage increase in intensity of the h 0 I. I # 2n. reflectionsin going from 14(1 К lo К) К strongly suggests (hat (lieordering I in the sense of a phase transition) is only partial at140 K. If true this strongly contrasts with the otherwiseseemingly similar KlbPO.; family where Ihe hydrogenordering and the distortion of the heav у-atom lattice gohand-in-hand.

Thus far no evidence has been found for a structuraltransition m BPI between 140 К and 10 K. although themost recent investigation al Laboratoire I.eon Brillouinof the temperature dependence of the additional reflectionsof the ferroelectric phase has suggested ill'1 formation of anintermediate phase around 210 K. Perhaps this is wheregradual ordering of the bridging hydrogens occurs?

At all temperatures it was clear that in BPI there is just asingle Hi 12) site near O(2). in contrast to B|> where twohalf-occupied sites between O(2) and O(.i) are preferred.The tola! transfer of Il( 12) to the helaine /witterion. asopposed to the partial transfer in BP and the total retentionir. the H;AsO4 group in ВЛ (inset to l-'ig. 1). is consistentwith the increase in acidity in going from Hy\s()4 to H-,P()jtoH,PO,.

Л lot of work lies ahead before u e can hope lounderstand fully the pure end members let alone thefrustrated phases of llie mixed crystals. The largeasymmetric units, particularly in the lower temperaturephases, demand extensive and precise diffraction data and

/•/i,'. 4 llu' niiili't utiir ^irin'liti'c\ i>l Ли' Mt> hi\lininlt>ltil/MiK.VIlHnyC/l'-CtlMfHl'Mfiil.h 11M, и I'M,',.( Mini i:l l'lt( 'si 'I'/, I /.

СП9)

СП81

у. .'ï. Muli't iiltir \lrncltiri' nj the Nh ht'ii:\'iic ci>mph'\

M'srRN

M = Ti, Zr, Hf M' = V, Nb, To M" = Cr, Mo, W

I- it;. .': l\o/(il>iil s/XT/V.s ч/ \>гчир •/. .ifwK\ i \ tin iniiifii чти/).

» 5 anil group f> nu'liil\.

careful analysis lo extract physical characteristics of thedifferent phases and phase transitions. This is particularly soin the frustrated mixed phases where additional occupationaland positional disorder occurs in the salt groups|vi/. ()|5)/HM4) in BP-BPI. and P/As in BP-BA. see theinset to Fig. 11. Deuteralion would alleviate the experimentalproblem of absorption, but can also change the nature of thephase transition. Indeed, deuteruted BA has anantiferroelectrie. rather than ferroelectric, low-temperaturephase and mixed crystals ol hydrogenous BA and deuteraledBA also form a frustrated polar phase: but that is a story fora later annual report!

COLLEGE 5

Half-sand» ich niobium iniido and molybdenumliiKiimido) complexes: mctallocene analogues

lient group 4 meialloccne derivatives (('pAîCN- whereM=Ti or / r . and C'p = cvclopentadiein I ) arc оГ currentinterest as precursors ю /legler-N.itla pol\ meri/ationealalvxtv Feilske-llall molecular-orbital calculations carriedinil on group 5 half-sandwich iniido and group d hislimido)fragments show that lhe\ nias be considered to be isolobal(Fig. .Ъ and electronicalh iso\ aient with the group 4ineiallocenes. The frontier orhilals available for thecoordinalion of further ligands ha\e been calculated to lie ina plane perpendicular to thai defined by the metal, the imidonitrogen and the cenlroid of the cyclopentadienyl ligand torgroup 5 complexes, and to the plane of the two imidonitrogens and the metal for group о compounds. Thestructures of three of these compounds - two Mo bislimido)complexes (Fig. 4.1 |.i|. and a rare example of a Nh ben/ynecomplex (F'ig. 5) |4| - ha\e been determined by single-er\ still \-ra\ diffraction. These structures were found to heconsistent with the predicted geometry around the metal.The structures of a number of other Mo bis( imido) and Nhhall-sandwich imido complexes have also been determined.(Collaboration with Durham I'niversitv ).

penetrate centimetres rather than microns of material and

thus unequivocally provide information about the bulk state

of internal stress.

Specimens were prestrained to 1.5, 4.5 and 8 CA

compressive strain, prior to reverse (tensile) straining. The

development of internal stress was monitored by intermittent

unloading and diffraction peak measurement (the strain

being calculated from the shift of the centre of a Gaussian

peak). The results are shown in Fig. 6 plotted against

cumulative strain (S|t'|) It can clearly be seen thai internal

matrix strains build up in similar sense (but of opposite sign)

under forward straining in both tension and compression.

The load is transferred from the matrix to the elastically

deforming particles, but plastic relaxation, local to the

particles, limits the rate of increase of load transfer and after

a few percent plastic strain the rale of increase of matrix

strain tcilIs considerably.

Neutron diffraction studv of the Biuischinger effectin a high carbon steel

The Bauschinger effect was noted as early as I.SK6 byJ. Bauschinger as "by loading in tension or compressionabove the elastic limit, the elastic limit for compression ortension respectively is lowered significantly, the more so.the greater is the initial loading above the limit". Despiteextensive research in the intervening years however, thiseffect, which is common to all inhoniogeneous materialsremains poorly understood. This is largely because the rolesof mismatched stresses between the phases and ofdislocation-based work hardening, as the load is reversed,have not been conclusively identified. To date tlv.; onlyattempt to distinguish between these two effects has been theX-ray work of Wilson and Bate |5|. In this respect. Braggdiffraction is a very useful tool enabling one to ireasure thestrains in individual phases via peak shifts, while thedislocation density is related to th peak width. A study ofthe Bauschinger effect has now been made by neutrondiffraction.

As in the early work on the Bauschinger effect, this studywas undertaken on a I.I r/< carbon steel heat-treated to give~17 '/i of spheroidal cementite particles. The neutronexperiments were carried out at the reactor of NPI Re/, nearPrag on a dedicated three-axis spectrometer equipped withelastic-ally bent silicon monochromator and analyser crystals.Thanks to a combination of real and reciprocal spacefocusing, it permits profile analysis at resolution conditionsapproaching those offered by X-ray equipment |6]. Neutronshave, however, the distinct advantage over X-rays that they

1000с

I 500u'E

—•-- compressiontension - 0%tension - 1.5%tension - 4.5%tension - 8%

'-5 0 5 10 15 20 25

cumulative plastic strain [%]

/•7,4. f>: The deve'opment of matrix strain as a functionofcumultilin' plastic straining for different annpressive pre.ilrains.The monotonie loading cun'ex are shown in hold lines.

While the load transfer increases the yield stress in theforward direction, it decreases it upon reverse straining,giving rise to the Bauschinger effect. This is because, uponunloading, the load transfer leaves residual stresses in thematrix, acting in a sense opposite to the forwarddeformation. Menée upon load reversal the residual stressesfacilitate a rapid reversal of the internal matrix strain, whichis fully achieved when the plastic strain approximatelyequals the prcstruin. The variation in diffraction peakwidth (FWHM) with forward and reverse straining is

COLLEGE 5

-о®0.12CN

.£ 0. 1 1

50.10-

0.09--30 -20 -10 0 10 20

Net plastic strain [%]30

/•V,i>. 7: Tin1 variation in diffrai 'tion peak width «л a function of MI(tensile) strain for different compressive prestrains. The monotonieloading curves tire sliinvii in hold lines. Symlxilx tin i» I'ig. f>.

displayed in Fig. 7. Again, there appears to he littledifférence between evolutions due to forward loading intension and compression. Immediately "upon load reversalthe width decreases abruptly - reflecting relaxation ofresidual matrix strains, also responsible for peak positionshifts. After a transient period the width becomes related tothe net strain rather than to the cumulative strain, reflectingthe evolution of the dislocation substructure under newconditions.

Crystallography and MagnetismMagnetic ordering and excitations in electron-dopedsuperconducting materials

The magnetic properties of high temperature-superconductors and related materials have beeninvestigated in great detail following the suggestion thatthese might play an important role in the superconductingmechanism. The Cu ions in these materials carry an unpairedspin and therefore it is possible that the magneticfluctuations are responsible for the Cooper pairing. Indeed,fluctuating two-dimensional antiferromagnetic spincorrelations in CuOi planes have been reported to exist up tovery high temperatures in these compounds and persist evenin the samples which are doped to become superconductorsand in which no magnetic transition occurs. The magneticproperties of the hole-doped superconductors La2.xSi\CuC>4and RBaiCu^O^ (R = rare-earth element) have beeninvestigated quite extensively. Superconductivity has alsobeen discovered in the class of materials Ri.xMsCuO4(R = Pr. Nd. Sm and Eu: M = Ce. Th) for which electrons,rather than holes, are the charge carriers. Systematicinvestigation of the magnetic properties of the electron-doped superconductors could further elucidate the possiblerelationship between magnetism and superconductivity.

The magnetic ordering of the parent imdoped materialsRiCuOj has been investigated for a number of rare-earthions. The Cu magnetic moments in RiCuOj order attemperatures in the range 250 - 285 K. The rare-earthmoments, when they are non-/ero. order at much lowertemperatures (1-6 K). Systematic neutron-scatteringinvestigations on RiCuO4 (R = Pr. Nd. Ku and Gd) wereperformed initially at the ILL. After the unfortunate shutdown of the ILL reactor several ILL scientists continuedthese investigations at other neutron scattering centres.

GdiQiO4 behaves differently to the rest of the R;>CuO4

family Although Gd-.CuO4 is as easily doped with Ce or '\\ias the other members of the family, it does not. as they do.become superconducting. Several explanations have beensuggested for the absence of superconductivity in thiscompound, hul they are not convincing. GdiC'uX^ alsoshows weak ferromagnetism below the copper orderingtemperature. The magnetic ordering of GdiCiiOj wasstudied at low temperatures by neutron diffraction at ILL |7|and it was found that below Т = 6.4 К the gadoliniummoments order antilerromagnetically with the wave vectork = (().(),()). Ferromagnetic Gd layers parallel to the a-b plane

f'ig. ti: Magnetic structure ofGd2Ct<Oj below T^Gdt- '>.4 K.Note that the spin directions of the Си tind Gd xiihlanicex чгеil/ right angles. The structure model assumes a xiitgle-i. orderingof the Си Mihlattice. Л doiible-k non-collinear spin arrangementis also possible.

COL I E G E 5

are antiferromagnelicallv stacked along [0011. The magneticordering of ihe copper sublatlice has also been investigatedbv neuiron diffraction al PSI |S|. The C4r+ ions in (id-,('n()4

order al T\- = 2S5 К lo a l.uiNiOj-lype antiferromagneticstruciure with the propagation veelor k = ( 1/2.1/2.0). l-'ig. Sshows (he inagnelic structure ol'CkUCuOj below 6.4 K. Theintensily of the 1/2 1/2 I magnetic reflection increaseseoniinuonslv v, iih decreasing temperature to 45 K. Belowthis temperature n starts to decrease and shows a minimumat about 20 К (Fig. 9). There is a further sharp anomalyat about 7 К at which the intensity of the reflection becomespractically /его. A search for magnetic reflections atQ = (1/2.1/2.0). (1/2.1/2.2) and (1/2.1/2.3) and otherincommensurate positions at 7 К did not reveal anymagnetic intensity |4|. This result indicates that at thistemperature three-dimensional ordering of the coppersublaltice disappears. The disappearance of three-dimensional magnetic ordering of the C'u suhlaltice justabove the ordering temperature of the (id sublattice isintimate!) connected with the weak ferromagnelismobserved in GdiCu()4 |l()|. Чп.се weak ferromagnetism isforbidden both for non-/e.o propagation vectors and in thetetragonal space group 14/mmm of GdiC'iiO.^ somestructural distortion which changes the periodicity andlowers the symmetry must be present. A model in which theoxygen atoms are displaced perpendicular to the ideal C"ii-O-('ubond direction in accordance with the X-ray measurementswas proposed [l()|. Of the two possible displacementpatterns the more likely is the one for which there is a realantisymmetric exchange interaction of the D/valoshinski-Moriya type between the nearest neighbours within theCuO;. planes. i| has been assumed that these displacementsare perfect!) correlated in each C'uOi plane, but there existsno correlation of displacements from plane to plane.This model provides a possible explanation for the natureof the transformations of the magnetic structure which occurat temperatures below 50 K.

The magnetic ordering of the Cu ions in a single crvstalof HibCuOj has been determined at MIST | I I |. Magneticreflections corresponding to the wave vector k = ( 1/2.1/2.0)develop below the Neel temperature T N = 265(5) K.showing a long-range antiferromagnetic ordering of the Cumoments in ЬдиСиОд. The low-temperature saturatedmoment was determined to be 0.4(0.1) |Дц. with the spindirections restricted to the a-b plane. Magnetic field-dependent studies show no hysterelic behaviour atintermediate temperatures, which strongly suggests that theantiferromagnetic spin structure is of the non-collineardouhlo-k type previously observed in SiibCuOj as well asNdjCuOj al intermediate temperatures.

The dispersion of the singlet-doublet magnetic excitonsof the Pr + ions in the singlct-ground-siale system Рг-ХЧЮдwas measured by inelastic neutron scattering at NIST |I2|.The excitons exhibit significant dispersion both within thebasal plane as well as along the c-axis direction, directly

demonstrating the Pr-Pr exchange interactions. Theseexchange interactions must be mediated through the CiiOihivers involved in Ihe formation ol the superconducting state.

The magnetic ordering of NdiC'uO4 al ini l l iKelvintemperatures has also been investigated bv neutrondiffraction al H MI 113|. At about Т = 400 mK the 1/2 1/2 0reflection which is forbidden for the magnetic structuredetermined at higher temperatures starts increasingin intensity and shows no indication of being saturated downto 33 mK. the lowest temperature attained during Iheexperiment. Other allowed reflections like 1/2 1/2 1. 1/2 1/2 2.1/2 1/2 3. etc. also show anomalous increases in intensitybelow 400 mK. These results strongly suggest inducednuclear magnetic ordering in Nd->C'u()_| below 400 mK.

The Surface Supercdiuluclinn Region in Lead

Above ihe crit ical applied f ield. l l c . for a bulksuperconducting stale of a type-l superconductorsuperconductivity persists within a narrow surface layer ofthe m a t e r i a l , a phenomenon k n o w n as surfacesuperconductivity and predicted within (lin/burg-l.andautheorv. The magnetic flux profiles within the surfacesuperconducting region of lead films has been measured bypolari/ed-neulron refleciometry on CRISP at ISIS and thevalidity of the Ciin/burg-Landau equations examined 114|.

10 20 30 40

Temperature (K)

I-/Х. Ч: Генцн'пинге YHIÏIIIIHII "I I/K' iiiififmiril inlcmitva/ /In1 1/2 1/1 I iiuixni'tir irllecliiin in the ifiiipeniliiri' ганцеIKH/I /.^ in 4? A' \lni\\ hit; и /'/чип! minimum ui cihuiil 20 К

i/iu/ ii /nrr/it'i' \IHIIÏ> minimum ul i/himi 7 A'. The /ir\l timaiitilvn ii\\ni-i4iftl\vitli I/if uctik li-rrtHiMwiiMii. ir/imvn the wmidtiniimt//\ !•, /тсг/т'ич.' lo hi' tine I» the ili\ni>i>ctiniiH4'a/ ;//c ilim'-ilinicmitHwl onlvrinn of the Си mti.viiflU тчтспн.ï'\\ ii-ilinii'iniiiiKil imiftiH'tic unlmnx in the CuO-, />luiw mini \;;7/cv/Ч/ ilnc In the \lriniv Cii-O-Cu SH/WWIC/KHI.IJC inlcnieliini.

COLLEGE 5

In these s tudies , the t rans i t ion I'nun the bulksuperconducting stale to the surface superconducting staleand the subsequent entire destruction of superconductivitywithin the material as и function of the applied field hasbeen directly observed (fig 10). Analysis of the measuredflipping ratio profiles has shown tha' in both the bulksuperconducting region and the surface superconductingregion, at applied fields away from the upper critical field.Hcv Gin/burg-Landau theory is valid and provides anaccurate model of the magnetic induction profiles within thematerial. At higher applied fields, close !<> Hci the fielddependence of the magnetic induction profiles may bemodelled by assuming that the characteristic Gin/burg-Landau parameter к. increases rapidly with an increasingapplied field.

l'hast Transition in I'chTiln

Recent measurements of the bulk susceptibility andresistivity of PdiTiln indicated a phase transition at 110 K.A broad peak in the susceptibility occurs around 1 К) Кsuggesting an ordered magnetic ground state. Above 110 Кthe susceptibility follows a Curie-Weiss law. This result wassurprising since none of the constituent elements is itselfmagnetic. In order to try to establish the nature of the groundstate, a powder neutron-diffraction experiment wasperformed using DN5 at Siloé.

Between 300 К and 92 К the neutron diffraction patternsare consistent with a single phase L2j structure with a spacegroup Fm 3 m ( o^ )• Below 92 К the patterns arecharacteristic of a crystallographic distortion from a cubicfee structure to a body-centred tetragonal one with spacegroup I4/mmm ( Dh7 ). The cell parameters of the cubic andtetragonal structures are related by a, = <i, / V2 and i; = at.The thermal variation of the laltice parameters and the unitcell volume determined from the neutron diffractionexperiment are shown in figures (II) and (12) respectively.At 92 К there is a huge discontinuity in the latticeparameters, consistent with a first order transition. The aparameter is seen to increase abruptly. Да/а = 0.35 r!<. whilethe с parameter decreases. Дс/е = 0.68 9r. In contrast thevolume shows no anomaly at 92 K.

Nor. in contrast to the static susceptibility data, did theneutron diffraction pattern show any evidence of long-rangeantiferromagnetic order, i.e. there were no additionalmagnetic peaks. Due to the extinction conditions associatedwith the body centered structure (h+k+l = 2n) the 001. 100,I I 1 and 102 reflections arc systematically absent. Theabsence of these peaks leads to the following conclusions:either there is no long-range untiferromagneiic order with asignificant moment, or there is only a ferromagnetic orferrimagnetic coupling of magnetic moments on twocrystallographically different sites, i.e. between Pd and Tiatoms. This would give a small contribution to the intensityof the nuclear Bragg reflections which would not easily bedetected in a powder experiment.

| 2 . 0V)

I 1 - 5

"5S50.5с

" c•ч— bulk supeiconducting— * .

region т * - surface-*т "superconductingI region

t ** "„ 'ï 1

ï0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

applied field (105 A m'1}

/•/.if. /".' '/'//c inlcfiriil nj the />oltiri~<ilioii over iiiiniiei.liiiii inui\/i'i'/'lulled iifiainsl llu1 d/>/>/icil field, Jor a le«<lJilri ч I.UK, II,is llie critical field Jor the Inilk sniicrcoiidiicliiifi stale mid II, (

ix the critical Jh'ld Jor the surface superconducting ..line.

'^6.380D

6.3206.300

0 50 100 150 200 250 300temperature (К)

/•'/,(,'. //.' The tliemuil variation of the lattice parameters a/ PdiTiln.

The results are consistent with an instability of the localmoment which would give rise to the structural phasetransition | I 5 | . More detailed analysis of the magneticmeasurements suggest that (he ground state is probablyferrimagnetically ordered, which would produce only asmall magnetic contribution to the intense nuclear Braggpeaks. In order to solve this problem, polari/.ed neutrondiffraction measurements on a single crystal are required.

The magnetic structure of UCo2P2

While UFeiP2 and UNbPi crystalli/.e with the body

centered tetragonal ThCriSii structure (I4/mmm).has a structure, which can be derived from that of ThCr->Si->

С О IL Е С Е 5

•2S 262.5

257.050 100 150 200

femperature (К)

250 300

/•V,i;. /.?.• ïïie variation of unit cell volume их a functionо/ lem/H'mtnre tifl'tl-iTHii.

The symmetry of the underlying magnetic structures inphases AF3 and AF2 is identical. It is incommensurate withthe crystallographic hitlice and can be described by apropagation vector k = (-0.214. 1/2. 0.457). In AF3 themagnetic moments are semi-ordered. The componentparallel to the a-c plane is sinusoidally modulated inamplitude, whereas the component perpendicular to the a-cplane, i.e. parallel to the |() 1 0] direction, is disordered.The phase transition from AF3 to AF2 on cooling involvesan additional oidering o: die component of the magneticmoments in the (0 I 0| direction, leading to an ellipticalspiral structure in AF2. The basal plane of the ellipticalspiral is spanned by the b-axis and the direction of themagnetic moments in AF3, the so-called easy direction.In phase AFI the magnetic .structure is commensurate withthe crystallographic structure, being described by apropagation vector k = (± 1/4, 1/2, 1/2), i.e. wild a magneticunit cell 4a, 2b, 2c. The magnetic moments are collinear andparallel to the easy direction in the a-c plane, forming anangle of 37° to the a axis, like the ordered part of themagnetic moments in AF3.

by an interchange of half of the Cr and Si positions.The resulting CaBeiGci-type structure has the space groupP4/nmm (fig. 13). In UCo-pPi the Co(l) and the P( 1 ) atomsare at 2a and 2b respectively, and the U, Co(2) and P(2)atoms are at positions 2c each with different /. values.

Both the uranium and the cobalt atoms of UCo2P2 carrymagnetic moments. Their order was investigated forpolycrystalline samples with a SQUID magnetometer and byneutron diffraction on D20 just before the shutdown |16].The magnetic cell (Fig. 13) is doubled along the с axis|k = (0, 0, 1/2)]. The magnetic moments of the uraniumatoms are aligned antiferromagnetically and parallel to theс axis with ц с ч р = 1.58(5) Ц|5 and a stacking sequence+ + --, + + --. Of the two cobalt sites only one shows orderwith the magnetic moments p^p = 1.14(7) Цц again alignedparallel to с and therefore parallel to the adjacent uraniummoments. In going to higher temperatures the order of theuranium moments disappears at 170 K, while the cobaltmoments still show considerable (antiferromagnetic) order.The field dependent susceptibility measurements in theSQUID magnetometer indicate that the magnetic order ofthe cobalt moments can be changed to be ferromagnetic byapplying a magnetic field.

The magnetic H-T phase diagram of MnWO4

Previous resu'ts, which were obtained by neutrondiffraction experiments on powders and single crystals,revealed that MnWO4 undergoes several magnetic phasetransitions below 13.5 К in /его magnetic field [I7|. Themagnetic phases are labelled AF3 (12.3 К < Т < 13.5 К),AF2(8.0K<T< 12.3 К) and AFI (1.2 К < T < 8.0 К).

/•"(#. /.?: Crystal anil magnetic .structure of UCo iP-,. The momentsof tht C<>(2) atoms which lie between two antiferrmmagneticatlvcoup/et! uranium layers, are disordered.

COLLEGE 5

Susceptibility anil magneti/ation measurements revealedthai there is at least OIK- further first-order phase transition.when a magnetic t'iekl is applied parallel to the easv axis.The transition field is II = 2.1 T. The I'iekl induced magneticphase uas characleri/eJ in more detail h\ a neutroiidiffraction experiment, which was performed on the normal-beam dil'fraclometer DN3 at the Siloc reactor of the (TINGrenoble. The field and temperature ranges investigatedwere 0 - 5 Т and 1.5 - Id К respective!;.. The magnetic fieldwas applied parallel to the easy axis.

It was found iluii the field-induced magnetic phase isidentical with phase AF2. B\ monitoring systematically thecount rate in the maximum of reflections corresponding tothe magnetic superstructures of the three magnetic phases asa function of temperature and magnetic field, all phaseboundaries in the given field and temperature range weredetermined. The phase diagram obtained from thisexperiment is shown in Hg. 14. It appears that phase Л1;2occupies the largest part of the magnetic II -T phasediagram, including a field-depeiuleni ferromagneticcomponent, which is 0.26 j.t|j at 11 = 3.8 T and T = 1.5 K.

Special care had to be taken in order to delect thetransition from AF3 to Al;2. because the satellite positionsof both magnetic phases are exactly identical. At thetransition from the paramagnetic stale to AF3 cm cooling welooked at a magnetic satellite which is strong when theordered magnetic moments are restricted to the a-c plane,i.e.. in phase A1-3. As the main difference between the phasesAF2 and AF3 is the existence of an ordered component ofthe magnetic moments parallel to the b axis in phase AF2. atthe transition AF3 - AF2 a magnetic satellite was selected,which gains considerable intensity only in phase AF2, i.e.one which is very sensitive to the presence of thiscomponent. This is visuali/ed in Fig. 15, where thebehaviour at /его field of two such reflections is shown oncooling from the paramagnetic state.

k=(-0.214, 0.5, 0.457)

AFlk=(0.25, 0.5, O.Sfi

• GIB

0 8 12

temperature (K)16 20

_ 3 2 5

-1.2140.5-0.5^-0.786 0.5 0.5^

Ц- Ч12 13

. i.^ — . i_

13 .,13

д Aл

* '.U 15 16 »

* * л , . - .** * * ** i

, ^ _ ^ i -._., , i .._, , i . — _ i _ . ,_^ i . ._^_

/•;'.!,'. 14: Magnetic H-Tphase diagram o/'MnW()j,when the applied external magnetic /icl</ it along the easy direction.

temperature (K)

/•'/ц. 15; Гетрсгапт dependence <i/ l/ie count rule in lite maximumi>/lite retlcclitiint- 1.214. 1/2. • OJ-UtatuH- U.7K(>. I/2.0.543),>liMit\\'()j. /У/с tmeiMiy of n-flwtioin- 1.214. 1/2, -0.541)A 'tinull hi'iwt'i'ii /.viS' A' (//;</nhinit 12 A'; // A sifinijtcdiiilyincmiwl til iihuiii 12 A', i.e. ui the phase transition Л1-2-Л/•'.<.whereat the reflet lion (-1). 7N6. 1/2. <).:>43) gaiitt intensity alreadytit a/null /.i..V Л'. /.c. at llie transition In phase AI'J on coiiling/гот lite paranitiKiit'iic stale.

The observed transitions result from a competitionbetween isoiropic exchange interactions and the weakanisotropy (L = 0 for Mn~+) of the crystal field. Consideringthe entropy contribution, which was determined by aspecific heat measurement, as well as the dipole-dipoleinteraction, the differences in exchange and anisotropyenergy at the phase transition AF1 - AF2 (E(AFI ) - E(AF2))can be determined by the use of mean-field equations.We find ДЕСЧ= 2.89 J/mol and ДЕ.ш1 = - 4.75 J/mol.

Secretaries: Garry J. Mclntyre (5a)BachirOuladdiaf(5b)

References

111 I. Fehsl. M. Paasch. S.L. Million. M. Braune.R. Bohner. A. Loidl. M. Dorffel. T. Nar/,S. Haussiihl and G.J. Melntyre, Ferroelectries 138

(1993) I - 10.

|2 | G.J. Melntyre. M. Paasch and A. Loidl.

(in preparation).| 3 | P.W. Dyer. V.C. Gibson. J.A.K. Howard and C.

Wilson. J. Organomet. Chem. 462 ( 1993) CI5-C17.|4 | J.K. Coekcroft, V.C. Gibson. J.A.K. Howard.

A.D. Poolc. U. Siemeling and C. Wilson.

J. Chem. Soc. Chem. Connu. (1992) 1668 - 1670.

| 5 | D.V. Wilson and P.S. Bate. Acta Mctall. 34

(1986)1107.

[6| J. Kulda. P. Mikula. P. Lukas and M. Koesis.Physiea В 180&181 (1992) 1041-1043.

CO U EG E 5

|7 | T. CliaUopailhyuy, P.J. Brown, A.A. Stepanov.P. Wyclcr, J. Voiron, A.l. Zvyagin, S.N. Barilo,D.I. Zhigunov and I. Zohkalo, Pliys. Rev. B44(1991)448(1.

|S| T. Chatlopadhyay. P.J. Brown, B.R. Kroner,N.K. Zayer a,\à K.R.A. Zieheck, J.Mag.Mag.Mat.127(1993)47.

|9 | T. Challopadhyay. P.J. Brown and B. Rossli.J. Appl. Phys. (in press).

11()| A.A. Stepanov, P. Wyder, T. Challopadhyay,P.J. Brown, G. Filliou, I.M. Vitehsky. A. Deville,B. Gaillard, S.N. Barilo and D.I. Zhigunov, Phys.Rev. 848(1993) 12979-.

1111 T. Chattopadhyay, J.W. Lynn, N. Rosov,Т.Е. Giïgeiïet. S.N. Baril» and D.I. Zhigunov.Phys. Rev. B (in press).

112| I.W. Summcrlin. J.W. Lynn. T. Chattopadhyay,S.N. Barilo and D.I. Zhigunov, Physica С (in press).

113] Т Chattopadhyay and K. Siemensmeyer,(in preparation).

114) M.P. Nutley. AT. Boothroyd, J.F. Gregg,D.McK. Paul, and J. Penfold (in preparation).

| \5\ B. Ouladdiaf, K.U. Neumann, J. Crangle, N.K. Zayer,K.R.A. Ziebeek and E. Ressouche,J. Phys.: Condens. Mat. (in press).

116] M. Rcehuis. T. Vomhot'and W. Jeitschko,J. Phys. Chem. Solids (in press).

117] G. Lautenschliiger. H. Weitzel, T. Vogt, R. Hock,M. Bonnet, A. Bohm. and H. Fuess, Phys. Rev. B48,(1993)6087-6098.

The Use of Neutrons and X-raysin the Study of MagnetismI.L.L., 21-23 January 1993

It is now more than 40 years since Clilï Shull and ErnieWollan carried out the first neutron experiments onmagnetism, studying polycrystalline MnO. In theintervening years, neutron scattering has revolutionised ourmicroscopic understanding of magnetism. The pre-eminentposition of neutron scattering as a microscopic probe ofmagnetism is now being challenged by an increasing numberof x-ray techniques, employing synchrotron radiation.Although the interaction of electromagnetic radiation withmagnetic electrons is much weaker than the neutronmagnetic moment-electron spin interaction, this iscompensated to a considerable extent by the enormousphoton flux and high brightness of recent (and future)synchrotron sources. X-ray magnetic scattering has mademany significant contributions to our knowledge ofmagnetism over the last few years. The high wavevectorresolution, well-defined polarisation and wavelengthtunability provided by synchrotron radiation have led to animpioved understanding of the magnetic structure of rare-earth metals (the "spin-slip" model), to the discovery ofresonant-exchange enhancement at absorption edges, and toa vast body of spin-dependent absorption phenomena

studied using both linear and circular polarisationtechniques. But neutron scattering has not stood still, withadvances in both techniques and applications.

What is interesting is that (here is not a confrontationalspirit between the proponents of neutrons and x-rays inmagnetism. Rather a spirit of educated compromise isemerging as it is realised that the two techniques usedtogether can add significantly to our comprehension. Thiscomplementarity is attested to by (he Workshop held atI.L.L. in January 1993, organi/.ed by W.G. Stirling (Keele).G.H. Lander (Karlsruhe). C. Veltier (ESRF). J.L. Marline/(ILL/Madrid) and P.J. Brown (ILL). Over 100 scientistsparticipated in a series of 23 invited talks. In addition 62posters were presented and a wide-ranging panel discussiontook place. The meeting united members of the neutron andx-ray communities who discussed topics as varied asmagnetic x-ray dichroism and flux-line lattices in high-temperature superconductors. The invited talks have beenpublished as a special edition of Physica В | 11; theseproceedings are a most valuable indication of currentadvances in the study of magnetism. The organisers aregrateful to the I.L.L. and the E.S.R.F. lev financial supportand to Diana Dijoux and Serge Clais.se for their enthusiastichelp with the organisation.

We dedicate this workshop to the memory of our friendand colleague Jean Rossat-Mignod, whose untimely death inAugust 1993 brought short a most productive scientificcareer. We shall all miss his scientific drive and originality,but. more importantly, his friendship and humour.

Bill G. Stirling and Gerry Lander

Reference \ I ] Physica В 192. I & 2 ( 1993)

IAEA Materials-Research WorkshopCollege 5 members were responsible for organi/ing an

Interregional Training Course on Nuclear Methods inMaterials Research under the aegis of the InternationalAtomic Energy Agency,Vienna. Eighteen students fromwider Europe and the developing countries spent two weeksat the ILL in May in both lectures and practical exercises.The four IAEA-invited lecturers, from Portugal. France,Britain and Australia, taught the systematics of powderdiffraction and small-angle scattering for the study ofmaterials, while ten local lecturers, mainly from ILL andESRF, highlighted and broadened the course with first-handaccounts of X-ray and neutron topography, kineticmeasurements by diffractometry, polymers, hightemperature superconductors, phase transitions by powderdiffractometry. neutron spectroscopy, multilayer andmonochromator production and testing, etc. Exercises andprogram exchanges on personal computers, and visits tolocal reactors and the ESRF were much appreciated by thecourse participants.

Sax A. Mason

C O L I E GE 5

Empirical and calculated thermal-diffusc-scatteringcorrections for single-crystal diffraction data

Garry J. Mclntyre

Introduction

For monochromatic X-rays or neutrons the elasticBragg reflections are observed superimposed onincoherent scattering and inelastic phonon scattering.The incoherent scattering is essentially removed by thebackground subtraction, but the inelastic phononscattering, also called thermal diffuse scattering (TDS),peaks at the same positions as the Bragg reflections, andgenerally can be removed only by calculation based onthe elastic constants.

Unfortunately, for many compounds the clasticconstants are not known, and corrections to the observeddata for TDS are not made, the principal consequencebeing a reduction in the apparent thermal displacementparameters. Given the differences amongst scangeometries used by different experimenters on differentdiffractometers, it is little wonder that there is often pooragreement amongst thermal displacement parametersfrom different experiments on the same compound! Herewe shall see that with minor modification of theexperimental technique, particularly in measurementswith a 2-D position-sensitive detector (PSD), a purelyempirical correction can be made.

A little background to TDS

For X-rays the ratio of the one-phonon TDS intensityto the integrated Bragg intensity is [ 1 ],

where the integration is over the reciprocal spacevolume swept out in the scan, and

= (l/q2)£jlh.ej(q)]2/lpVj(q)J (2)

is the one-phonon scattering at q from the reciprocal-lattice point h, where kB is Boltzmann's constant, Т isthe temperature, p is the crystal density, vc is the unit cellvolume, Vj(q) is the velocity of the acoustic lattice wavewith vector q, and the ej(q) (j =1,2,3) are unit vectors inthe direction of polarisation of the lattice wave.

Jj(q) can be calculated from the elastic constants

Hjmn 12],

where Ay = I m , n c i j m n q m q n and the hj and q, are thedirection cosines of h and q respectively.

If the finite resolution of the diffractometer can beignored the 1/q2 dependence of J|(q) permits reductionof the 3-D integral over the volume of the scan to a 2-Dintegral over the surface S of the scan volume, which, aswell as allowing the singularity at the origin to beavoided, considerably reduces the calculation time [3].The expression for a.\ then reduces to

oC|=(kBT/vc)/sJ|(g)g</AcosC (4)

where g is the vector to the surface element d\ onthe surface S and Ç is the angle between g and the normalto il A.

For neutrons, the calculation of J|(q) is a little morecomplicated since equ. U) is strictly valid only for thescattering of neutrons that are faster than the velocity ofsound in the crystal, from a crystal with clastic isotropy.Calculation of a valid correction tor slower-lhan-soundneutrons or for neutrons scattering from crystals withsignificant anisotropy is complicated [4]. A reasonableapproximation is to accept in the summation of equ. (2)just those lattice waves with velocity less than theneutron velocity (5|. Fortunately most crystallographicstructural studies at reactor sources are made at neutronwavelengths for which equ. (2) does apply.

Even less background to PSD's

The recent introduction of 2-D PSD's has broughtabout a minor revolution in single-crystal diffractometry16]. One important advantage is that of optimaldelineation of peak and background in the 3-D array ofcounts observed around each reflection (Fig. 1 ). This isparticularly important for weak peaks on a highbackground. For weak peaks the envelope that minimizesthe relative error due to counting statistics lies in factwithin the instrumental resolution volume [7| - hardly acondition that satisfies the derivation of the TDScorrection in equ. (4)!

With minor modification though, equ. (4) can beapplied both to weak and to strong peaks, and correctionfor TDS is easier for 2-D PSD data than for conventionaldetector data lo the extent that a purely empiricalcorrection can be made.

Correction of PSD data for TDS

a) The idealised situation

A very important implication of equ. (4> is that if thefinite instrumental resolution can be ignored the amountof TDS included in a pyramid whose apex is at thereciprocal lattice point (relp) is directly proportional tothe height of the pyramid, i.e., to the distance from therelp to the integration boundary. Consequently, forintegration envelopes of the same shape but different

COLLEGE 5

size, the amount of TDS included in the integrationvolume is directly proportional to the average radius ofthe volume, whereas the amount of incoherent (flat)background is proportional to the cube of the radius.Similarly the contribution of two-phonon TDS isproportional to the square of the radius (Fig. 1 ).

By sampling each reflection in 3-D, as is donein scans with a 2-D PSD. we could correct empiricallyfor TDS, and even deduce the elastic constants.The precision in such an empirical method would bepoor for weak reflections, especially if sitting on a high'flat' background, but, because of the slow globalvariation of TDS with the scattering vector, thecorrections for these reflections can be estimated fromthose of nearby strong reflections.

Alternatively, if the elastic constants are already wellknown, the TDS correction to the peak and background

Fig. 1: The 3-D distribution of counts observed aroundthe 261 reciprocal lattice row ofmonoclinic NiSOj.ftHiOin a single scan on DI9, The iso-intensity contour shownis 10% of the maximum count observed in this scan,and for the strongest reflections corresponds very closelyto the size of the reflection integration envelope.

integration volumes can be calculated by evaluating equ.(4) for a series of pyramids that f'l! the integrationvolume, in the same manner as in existing algorithms forsingle-detector data.

A convenient division is In terms of the polarcoordinates 6 and ф. Often an ellipsoidal integrationenvelope is assumed, since it is a good approximation tothe instrumental resolution volume. If the integrationellipsoid is described by,

e x V +ey-y2 + e /

2 7 2 = I

and 6 and ф are with respect to the principal axesof the ellipsoid then

g = (exsitr9cos +Cy"siir0sin0 +e /cos0)"-(5)

and in equ. (3) gc/AcosC = gunQclQdty

b) The real situation

Unfortunately, if full advantage of the PSD is takento minimize the counting statistics of backgroundsubtraction by using integration envelopes similar to orsmaller than the resolution volume, v/e are far from theideal situation. A correction for finite resolution must beincluded.

=* J|(q) in equ. (4), is replaced by iR(q') J|(q -q')i/3q'

If we consider just one pyramid, i.e. just one directionin reciprocal space from the relp, the convolutionbecomes one of R(q') with g. For convenience theconvolution is broken into two parts:

fig. 2: The relative contributions of Bragg intensity. TDS andbackground to the total intensity within integration volumesof the same shape but different size in the idealized situationof an infinitely small resolution function. I is the integratedBragg intensity, T/ the one-phonon TDS, T2 the two-phononTDS, and В other (uniform) background.

COLLEGE 5

a) Fraction of the resolution volume insidethe integration volume

We can assume tiiat the integration volume has thesame shape as the iso-probability contour of theresolution ellipsoid. If in our example of an ellipsoidalresolution function we choose as integration variables,x' = ex~x. y' = ev"y. z' = e7"z, and shift the ideal g outsidethe integral, then R = R(r') = R((x'2 + y'2 -t- z'2)' / 2) andthe integration over R is within a sphere of unit radius.The direction of the pyramid axis is no longer 0,фin these coordinates but since x', y' and z \ an identicalranges, the integral itself is independent of 6 and ф.With the help of Fig. 3, we can deduce that theconvolution of the resolution function with the distanceto the integration boundary is,

g j R(x'2+y'2+/'2) - x'2 - y'2) - •/.'] (6a)

where the integral is over just those points for whichx'2 + y'" + /'- < I.

b) Fraction of the resolution volume outsidethe integration volume

The integrand is now the distance through theintegration volume, parallel to (sin0cos0,sin6sin<|>.cose)weighted by the resolution function. Similarly this can betransformed to integration outside a unit sphere, with gof the ideal situation as a prefactor,

resolution ellipsoidsmaller than

integration ellipsoid

transformedto a sphere

rotated to beparallel to z

resolution ellipsoidlarger than

integration ellipsoid

transformedto a sphere

rotated to beparallel to z

Fig. 3: Reduction of the resolution convolution to integrationwithin a unit sphere. The dashed ellipse or circle is theboundary of the integration envelope; the heavy ellipse orcircle is one iso-probability contour of the resolution function,all in reciprocal space. The arrows are the vectors for one pairof polar angles from selected points within the resolutionfunction to the integration envelope.

gjR(x'2+y'2+/-'2)V(l -x'2-y'2)</xV/yVz' (6b)

where the integral is over just those points for which."> , "> , "> ^ « i . т ', т ^ ,

x -f у +/ - a 1 and x - -ну - < I,

The total resolution factor is the sum of (6a) and (6b),and can be evaluated numerically for the range of ratiosof integration-envelope radius to resolution functionFWKH expected in an experiment (Fig. 4). Theresolution factor is the same for all 'integration'pyramids of one reflection.

The background is estimated from the counts in anouter shell that is not necessarily contiguous to the peakenvelope, but with inner and outer boundaries that wouldnormally be chosen to have the same shape us the peakintegration envelope. The contribution of one-phononTDS lo this background 'measurement' is simplyproportional to the difference between the inner andouter radii multiplied by (different) resolution factorsgiven by equ. (6a).

The resolution factor for two-phonon TDS is derivedin a similar manner, and is,

g | R(x'2+y'2+z'2) [V( 1-х'2 - y'2) - г']2 dïdy'd? (7a)

+ gJR(x'2+y'2+z'2)l7.'h/(l -x'2-y'2)</x'</yV/z' (7b)

Within the usual assumptions of TDS theory, anexact correction for TDS can thus be made, even withfinite instrumental resolution. The sampling afforded bythe present 2-D PSD's, especially in X-ray diffraction,will ultimately limit the precision of this correction andits use as a method to estimate elastic constants. The veryfine sampling offered by newer detectors based oncharge-coupled devices might be used to advantage inthis regard. With continously variable apertures it would

010203040.5060.70809101.1 I 21 31.41 5161.71 81920FWHH of resolution function/radius of integration ellipsoid

Fig. 4: Kesohttion factors for one-and two-phonon TDSfora 3-D Gaussian resolution function versus the ratio of theresolution function FWHH lo the radius of the integrationenvelope. The integration envelope is assumed to he aniso-prohahility contour of the resolution function. The totalresolution corrections for one- and two-phonon TDS areR/' + R/"andR2' +• KI" respectively.

COLLEGE 5

even be possible to make an empirical correction with asingle detector, but with much poorer precision than witha 2-D PSD.

Conclusions

The differences in the dependence of thecontributions to observed Bragg reflections, from one-phonon TDS, from two-phonon TDS, and frombackground, on the size of the integration volume can beexploited to correct for TDS and to estimate the elastic-constants empirically, provided each reflection issampled in three dimensions, as in scans made with a2-D PSD. Finite resolution introduces additionalgeometric factors which can be calculated exactly if theintegration volumes are iso-probability contours of the3-D resolution function. These are strong reasons, inaddition to that of minimum relative error due tocounting statistics, for making 'routine' single-crystaldiffraction measurements with a 2-D PSD.

References

11 ] W. Cochran, Acta Cryst. A25 (1969) 95-101.

[2J W. A. Wooster, Diffuse X-ray Reflectionsfrom Crystals, Oxford University Press, Oxford,(1962) pp 59-67.

[3] C. B. Walker and D. R. Chipman,Acta Cryst. A26 (1970) 447-455.

|4] B. T. M. Willis, Acta Cryst. A26 (1970) 396-401.

[5] M. Merisalo and J. Kurittu, J. Appl. Cryst. 11

(1978) 179-183.

[61 G. J. Mclntyre, Neutron News, 3 (1992) 15-19.

[7] C. Wilkinson, H. W. Khamis, R. F. D. Stansiicldand G. J. Mclntyre, J. Appl. Cryst. 21 ( 1988)471-478.

Spherical Neutron Polarimetryand Magnetic Diffraction

Francis TASSET

Introduction

In the neutron-scattering cross-section, the basicmagnetic scattering amplitudes are vector quantities, themagnetic interaction vectors Q(k). These are projectionson the plane perpendicular to the scattering vector kof the magnetic structure factors M(k), those vectorsbeing in fact the various Fourier components of theperiodic magnetic density M(r). For complex magneticstructures, in particular non-collinear ones, it has beenshown 11, 2| that the measurement of the magneticintensity alone may not be sensitive enough to determinea unique solution. Neutron Polarimetry, which measuresin addition changes in the neutron polarization, can givemore direct information on the directions of the magneticinteraction vectors. Therefore neutron polarimetry is animportant method for distinguishing amongst "differentmagnetic orders which may have the same or verysimilar magnetic cross-sections" [3|.

There are actually two forms of neutron polarimetrywhich we shall now briefly describe:

- Uniaxial Polarization Analysis (UPA), is theanalysis of the initial and final polarization componentparallel to an applied magnetic field. It was firstintroduced in 1968 at Oak Ridge by Moon, Riste andKoehler [4]. In magnetism, it has contributed to the studyof paramagnetic scattering 15], can detect non collinearcomponents in ferri-magnetic arrangements [6|, and helpto separate magnon and phonon peaks in caseof ambiguity.

- Spherical Neutron Polarimetry (SNP), which betterexploits magnetic scattering, requires a measurementwhereby all three components in both the incident andthe scattered polarization are set and measuredindependently.

Presently, with our polarimeter CRYOPAD(Cryogenic Polarization Analysis Device) [7], we areable to accomplish such measurements in zero appliedfield. In section 2 we shall explain why UPA is the onlysimple technique compatible with an applied magneticfield or a magnetised sample. In section 3 we shallrestate the theoretical formula which gives the changeof the neutron polarization vector in the microscopicmagnetic interaction. This complicated formula isnecessary to interpret SNP, and we show thatit comprises the spectroscopic subset, introduced withUPA. In Section 4 we present a single generic figure forthe possible changes in the neutron polarisation vectorinduced by magnetic structures containing centre

C O L L E G E 5

of symmetry and magnetic/nuclear interference terms.The depolarization effect due to the presence of 180°magnetic domains is incorporated, it illustrates theimportance of SNP being able to distinguish a truerotation from a simple depolarization effect.

Spherical Polarimetry

Basic principle

The principle of the measurement is very simple asillustrated in Fig.l. The polarization vector of theincident beam is set in the desired direction, then thecorresponding cross section and the direction andstrength of the scattered beam polarization vector isdetermined for a given Bragg reflection.

Zero-field implementation, the CRYOPAD

Although it looks simple, such a completemeasurement of the scattered neutron polarisation is noteasy. If, as usual, we use a magnetic field to guide thepolarization at the sample position, it plays an adverserole. The transverse component of polarization createdby our sample (see sections 3 and 4) starts Larmorprecession at high speed; due to field inhomogeneitiesand dispersion in speed, it relaxes and is lost veryquickly.

To handle a proper measurement of this componentits precession from the sample axis to the analyzingsystem must be controlled precisely. Spin Echotechniques could be developed in that direction, but withCRYOPAD we attack the problem in a different way: thesample is kept in zero field, low enough to suppress"parasitic precession" and to isolate the true effectof scattering and measure it, as in figure 1.

Using Magnetic Meissner Shields

The polarizer and the analyzer system used on (N20are based on saturated magnetic crystals and they requirehigh magnetic fields (2000 Oe) which unfortunately givesubstantial stray fields. Knowing that even the earth fieldmust be eliminated, we have to provide magnetic shieldsaround the sample chamber. Superconducting Meissnermagnetic shields are the ideal solution to this problem.With Niobium being transparent to neutrons and to theirpolarization we have designed an almost closedcylindrical sample chamber. The exit point for thescattered beam being far enough from the entry point, weought to apply two different guide fields of arbitrarydirections in order to transport adiabatically thepolarization to and from the sample chamber. But thisideal scheme is not directly applicable due to theboundary condition at the superconducting surface.Because all magnetic fields are necessarily tangent to

sample

nuclear

MMmagnetic

riser to analyser

/•'/д. /: The Polarimetric neutron diffraction experiment:tin1 polarisation vector of the incident ht'tiin P is net in thedesired direction. Neutrons scattered at momentum transferhk/2jt experience the corresponding Fourier componentof the nuclear potential N = N(k) and of the effective magneticinteraction vector Q = Q(k). The direction and strengthof the final polarisation Ps are kepi in zero field untilthey lire measured downstream (see text).

such surfaces (Bn=0, parallel flux flow condition) it isnecessary, in order to analyse an arbitrary, non transversedirection to proceed in two steps and use two successivescreen/field combinations [7|. First, we use a calibratedtransverse field to make the spins process untilthe polarization becomes transverse. Then it enters intoa strong nutation guide field which can be orientedin the transverse plane. Using these two magneticfields, precession and nutation angles are preciselydetermined by using algorithms based on the detectionof zero final polarization values [8]. The finalpolarization is measured with the classical analyzingsystem available on 1N20 comprising a DC neutron spinflipper, a polarizing Heusler crystal and a neutrondetector. A similar, reversed arrangement is providedto control the incident polarization direction. Moredetailed explanations on CRYOPAD can be foundin references [3, 7, 8].

The microscopic theory for neutron polarimetry

The vectorial formalism

The change in neutron polarization for a mixedmagnetic nuclear scattering process has been worked outin its present form by Blume[9]. With k beingthe scattering vector, N= N(k) the nuclear structurefactor and M=M(k) the magnetic structure factor,we have to introduce the magnetic interaction vectorQ = Q(k) which is the projection of M on a planeorthogonal to k

Q(k) = kA (M(k)A k) (1)

COLLEGE 5

Then we have the following expressions for Ihescattered neutron intensity I and the scatteredpolarization vector Ps where P is the polarization beforescattering:

I = NN* + N P.Q* + N*P.Q* + Q.Q* + iP.(Q*AQ)(2)

Psl = PNN* + QN* + Q*N - i (PAQN*-PAQ*N)+ Q (P.Q*) + Q* (P.Q) - P (Q.Q*) - i(Q*AQ) (3)

N and Q have to be expressed in the same units usingthe following scale factor:

1цв = 0.2695 КГ12 cm (4)

The four scattering cross sections in UP A

When introducing the UFA method. Moon, Riste andKoehler [4| did not use Blume's vectorial theory forneutron polarization rotation. Instead they derived amore spectroscopic set of four partial scatteringamplitudes connecting the two initial and final neutronspin states. With our notations the correspondingexpressions for the partial cross sections are:

O - - = | N - Q

theory predicts the true change (rotation and length) ofthe polari/.ation vector while Moon, Riste and Koehlerpartial cross sections can only tell us the ratio of thescattered to initial polarizations in a single, yet arbitrary,/. direction. We conclude that these partial cross sectioncan be used safely when applying a magnetic field atthe scattering centre as long as the incident polarizationhas been strictly driven (or has relaxed) to this fielddirection (i.e. no transverse component should exist atthe scattering axis which might be re-injected into thescattered longitudinal polarization). We note also that theanalyzer must measure only the longitudinal componentin the scattered beam, but this is a built-in property in theferromagnetic analyzer crystal generally used.

The outcome uf vectorial polarimetry

Let us suppose that we have been able to grow asingle crystal which is a random alloy of the two existingisomorphous phases a FeiO^ and СгтО^. Like thepristine phases, the unit cell is rhombohedral with fourtransition metal atoms in two centrosymmetric pairs onthe 3-fold axis. These two phases normally have differentperiodic magnetic arrangements in the unit cell, which issymbolized by a and p in Fig. 2. At low enoughtemperature, both are collinear arrangements withthe spins aligned on the unique axis, but they differ in anessential way: spins in a. obey the centre of symmetry,spins in P do not. Therefore magnetic structure factors

If we assume that we know the initial polarizationvector P is in the z direction used in their formulae(n+ and n" being the number of parallel and antiparallelneutron spins in the incident beam), these spin-flip andnon spin-flip cross sections can be substituted into thefollowing appropriate definitions in order to determinethe predicted scattered polarization P," .

P = PÏ; P = - ^ r ;

n*+n;n++n~

Using now the value for PS.I from Blume's equation(3) we find that the UFA scattered polarization PS" canbe expressed simply as:

P Ppu _ * s - r

4 ~ P(11)

This means that the UFA final polarization P" is onecomponent of the rotated final polarization Ps thecomponent which is collinear with the initial P. There isno contradiction between the two theories: Blume's

domain population

/ 2 phase

magneticarrangements

FIR. 2: Neutron Polarimetry on centric antifenomagneticarrangements: the measurement of the scattered polarisationvector Pjfrom mixed magnetic nuclear reflections givesinformation on the ratios Q/N, including the phase,and on the magnetic domain populations (see text). The fourbasic arrangements shown in the box produce pure rotationsand the corresponding final polarisation tips are indexedon the sphere. Only lite incoherent superposition of domainscan produce a reduced polarisation Ps.

С О I I F. G f: 5

in a arc in phase with nuclear ones, in (3 they are inquadrature. In addition each structure has two 180°domains which we have shown as Rand JÎ .

Blume's Formula (3) is difficult to handle in itsgenerality [10] but il is made easier to understand bystudying its geometrical concequences in a particularcase. Suppose that we have the initial polarizationvertical, that we have put the 3-fold magnetic axis in thehorizontal plane and that we are looking at a Braggreflection in the same horizontal plane with CRYOPAD.From the scattered polari/ation vector Ps. SNP canextract three pieces of information.

1) The4 length of the magnetic interaction vector inunits of the nuclear amplitude is given by the residual /vertical component of polarixation.

2) The phase of the magnetic interaction vectorrelative to the nuclear phase is given by the directionof the horizontal component. If it is in the direction ofthe scattering vector k, it indicates phase quadrature(ex: N is real Q is imaginary); if it is orthogonal to k(as Q is) then they are in phase.

3) Having a 180° domain simply reverses thedirection of Q. Therefore the corresponding points a, aand P, P corresponding to pairs of domains have thesame z component and П phases. For single domainscattering we expect no change in the initial polarization(assumed to be 100%), therefore the points lie on the unitsphere of final polarization vectors.

The existence of several domains in the sample willgive an "incoherent" superposition of such scatteringcontributions. The z component of polarization, being thesame for each domain, remains constant. On the otherhand the horizontal components of the polarizationvectors are not collinear, so that their weighted sum isreduced in length and the polarization tip moves towardthe 7. axis. This true depolarization effect which affectsonly the horizontal components tells us about theproportion of 1 80° domains.

Using the UFA arrangement, only the z verticalcomponent of polarization could have been collected,information 2) and 3) would be lost. SNP is thus thesuperior method.

CRYOPAD we could remedy this situation in the caseof non magnetized samples in a strictly zero field. Thisallowed us to solve several difficult antiferromagnetiestructures and to show the potential of the method.The measurement is of a superior nature because it givesthe transverse components of the final polarisation whichdistinguish a true depolarisation from a simple rotation.But the zero field condition is central to the techniqueused and cannot be overcome easily. Thereforemeasurements on magnetized samples and thoserequiring an applied magnetic field will still rely on theclassical Uniaxial Polarisation Analysis techniquedespite its other limitations.

Acknowledgments

The work described in this paper has beenaccomplished in collaboration with P. J. Brown,.1. B. Forsyth and V. Nunez. For technical assistance weare greatly indebted to S. Pujol who built the CRYOPADand J. Allibon who wrote the acquisition software.

References

11 ] P.J. Brown, et al., J. Phys.: Condens. Mat.,

3(1991)4281.

[2] M. Aïn, et al., J. Phys.: Condens. Mat,

4(1992)5327.

[3] P.J. Brown, Physica B. 192 (1993) 14.

[4] R.M. Moon, T. Riste and W. Koehler,Phys. Rev. 181(1969)920.

[5) K.R.A. Ziebeck and PJ. Brown, J. Phys. F.

10(1980)2015.

(6| F. Tasset, Physica B. 174 ( 1991 ) 506.

[7] F. Tasset, Physica B. 156-157 (1989) 627.[8] P.J. Brown, J.B. Forsyth and F. Tasset,

Proc. R. Soc. Lond. A. 442 (1993) 147.

|9] M. Blume, Phys. Rev. 130 (1963) 1670.

[10] V. Nunez, et al., Physica В, 180&181 (1992)903.

Conclusion

The theory of Spherical Neutron Polarimetry hasbeen given 30 years ago but, because of seriousexperimental difficulties, it has only been exploitedlately in systematic neutron diffraction measurements.Therefore, magnetic neutron scattering was not exploitedto its full potential, in particular for the determinationof magnetic structures. By building the instrument

* This is a short, adapted version of:"Magnetic structures and neutron polarimetry "presented at the Symposium in Memory ofRemy Lemaire"Magnetism of Rare Earth Intermetallic Alloys"Grenoble, Lab Louis Neel, 2 July 1993.© Journal of Magnetism and Magnetic MaterialsVol. 129 (1994).

COLLEGE 6

Liquids, Disordered Materialsand Metal Physics

Members of the College at ILL

I. AndersonT. BaumbaehM. BoudardP. ChicuxJ.C. CookA.J. DianouxC. DollD. DuhosB. FaragoB. FrickF. GiithoffЛ. HeidemannC. Janot

Kxternal members

M. Anne (CNRS)J.-P. Beaufilsi ENS Lyon)P. Becker (CNRS)M. Bée(UJF)M. Benmouna (UJF)F. BleylINPG)A. Bourre! (CENG)J. Bouvaist (Pechiney)Y. Bréchet (INPG)A. Chamberod(CENG)B. Chenal (Pechiney)A. Cohen-Addad(UJF)F. Cyrol (CNRS)P. Desre(INPG)J. Dupuy (Univ. Lyon)B. Fak(CENG)P. Guyot (INPG)

G.J. KearleyC. Larligue(CNRS)H.J. LauterJ. F. LegrandP .indnerA lagerlH lulkaR. Oeser0. RandlC. Ritter(). SchiirpfJ.-B Suck.1. Wutlke

A.-M. Hecht(UJF)J. Hilluirel (CENG)J.F. Jal (Univ. Lyon)F. Li vet (INPG)Y. Maréchal (CENG)1. Morfin (UJF)J.P. Morlevat (CENG)M. Pineri (CENG)C. Poinsignon (UJF)D. Quenard(CSTB)G. M. Raynaud (Pechiney)F. Rieutord(CENG)M. Rinaudo(UJF)G. Robert (CENG)P. Saintbrt (Pechiney)F. Volino (CENG)A. Yavari(INPG)

Although I993 represents another year without neutronsat ILL the strong support from colleagues at other neutronscattering centres and institutes has enabled collegescientists to continue and diversify their respective lines ofresearch as witnessed by the interesting range of resultshighlighted below. Towards the end of the year theexcitement of the approaching reactor start-up began to hefelt as preparations continued to prepare the instruments.We look forward to a successful 1994.

Low frequency excitations in glasses

The origin of the Boson peak, which appears inamorphous systems as an inelastic excess intensity (around0.1-5 meVi over the calculated Debye contribution, is notwell understood theoretically. Attempts at elucidating itsorigin have been made by comparing the Boson peak asmeasured on polymer glasses with different microstrucUirewhich differ b> the mobility of their melt. The Boson peak is

shown in F'ig.l at temperatures far belou T,, for se\eralamorphous polymers and is compared to trans-1.4-polv butadiene, a highly crystalline polymer, which does notshow the excess intensifs.

The interesting aspect of this comparison is the fact thatthe Boson peak position shifts towards lower frequencies,when passing from sterically hindered polymers,like poly(isohutyiene). toward1- very flexible polymers, likepolyfdimethvlsiloxanel or polyl\inylchloride). The peakposition is plotted in Fig 2 as a function of the monomericfriction coefficient (deduced from shear \iscosiiy) andshows a clear correlation between a diffusional properlyaho\e T,, and a \ihrational properly below T,,. As a reminderwe note that neutron spin echo experiments on very differentglass formers had clearly shown that the observedmicroscopic relaxation aho\e T,, follows the sametemperature dependence as the friction coefficient, whichhas been deduced from the macroscopically measured shear\iscosiiy. The Boson peak is attributed to vibrational orlirmitional modes in the disordered system and inconsequence it is proposed that the mobility of molecularunits abo\e T,, determines how the system is fro/en or

.OxlO3

+ pid3_140_5x pep_140_5x pbhtr_140_5a pib 140_5Opbh_140_5о pdms_140_5n• pid8_140_5

0 2 4 6

energy (meV)

/•'/.i;. /: Bd.Miii />i'i/k o/ .spvcra/ polymer .if/tmcv mih differentmobility metiMired on li\'f>. The cryMiilline polymerlmn\~fJ(il\'hiil(uficnc (lut'\ ntil s/jmr ihi\ c.M'ititlion.

COLLEGE 6

-aiофо.о1Лоса

-8 -7.5 -7 -6,5 -6 -5.5 -5 -4.5 -4log (@T + 100 К; dyn s/cm)

l-'ig. 2: Kncrgv lor the lio.son i>en(, nia.\ii/iiiin <vs <t function oj theinoiioiiiericJriciion coefficient a! Tv = 101) A'. Obviously ч higher/riciiiin cnejficient is related to a higher energy for the peak

measurements on poly (isobuiylenel (-(СТЬ-ОСН^ьИ. Theyattributed the observed excess intensity to tunnelling andfound tin inelastic form factor which reaches a maximumjust at the limit of the experimental Q-range. The aim ofexperiments on polyisohutyleiie carried out at the thermaltriple axis instrument BT4 at NIST | l | . was to extend theQ-range above (i A . where for the proposed parametersa maximum of the inelastic form factor and a furtherminimum should be observed. Several temperatures and twodifferent sample thicknesses gave the result that the inelasticintensity can well be explained by vibralional propertiesonly The inelastic intensity, corrected for Bose occupationfactor and the Dehye Waller factor deduced from the elasticscattering, follows nicely a Q--dependence for alltemperatures as shown in Hi». 3 and thus contradicts theproposed tunnelling model as origin.

(Jlass transition dynamics

.1. Wutlke and W. Petry continued their investigationsinto the glass transition dynamics of simple organic liquidsin collaboration with К l-'ujara and l-l. Sillescu (Unix1. Main/).As a model case which is intermediate between fragilemolecular systems and strong network glass formers.

trapped within the metastable states of the complex energylandscape of the glass. Another known experimental result,namely the fact that network glasses exhibit the Boson peakat even higher energies fits nicely into this picture.

Recently it has been proposed that phonon assistedtunnelling should be the origin of the Boson peak. Kanyaand co-workers have compared model calculations fortunnelling within an asymmetric two level potential with

0.80.7

5f 0.5

I °-4

£ 0.2(Л

inelastic scatteringat E = 2.8 meV;corrected fot DWF

270 К :

Fig. .•?: Inelastic form factor of the lioson peak for i>ot\isobiil\le»ecorrected for the !)el>ye-Wnller file/or a* deduced from /he elasticscattering. The solid line shows a Q~-dependent In ' " ' '" ' data asexpected for vibrations.

(о/2тс (GHz)

/•'/#. 4: SUM eplibilhy %^"Kal = (OS (t/wl ofneiiti'iin xcaiifiiiif;.divided by <i /iiclor /i:\;(t/> in order lo shim' the li/.toht'tu'lorirtilioii/>n>/>ert\ «I both t/ie Kmon pent, mid /he inierniedinle p-reltiMiiionregion. Light scattering fcontinuous lines! shows esseniinll\ l/icMine dynamic regime*, even iftlierc tire some obvious tiiuintiltilivedifference*.

С О L L Е G E 6

the associated liquid glycerol was studied by twocomplementary techniques, incoherent neutron scatteringand depolari/.ed light scattering. Neutron scatteringexperiments on C^IIslOD)? were performed with(i. Codtlens at the Mihcmol tinie-of-flight speclronieter atSacluy: light scattering in normal glycerol was measuredwith J. Hernande/. Ci. Li, and H. Cummins at the CityCollege of New York.

In the susceptibilities XNilP"1! = <"SN,L(q(l>)- I w i ) maximacan be aitrihuted to structural relaxation (d-peak) and toexcess phonon scattering (boson-peak). Both presentcharacteristics that are known from many other glassforming materials. In addition, there is a smooth, non-trivialcontribution filling the gap between both peaks whichresembles the anharmonic locali/ed motion (last (i-proccss)observed previously in fragile liquids and described by modecoupling theory (MCT). In this region (as well as for theharmonic excitations in the Boson peak) the spectral shapeof the neutron scattering susceptibility XN!<"> = XN(q<u|/hiv(q)is independent ol c| (Fig. 4).

This property makes it possible to compare XN(">!d i rect ly to the suscept ib i l i ty xi>>) = X Ï W n . o flight scattering measured at a much smaller q (4. КГ1 А"1'.Over the full range, both methods probe the same dynamics.Even in the q-dependent oc-rclaxation regime the curves

coincide, indicating that depolari/ed (2nd order) lightscattering couples to particle motion on a molecular lengthscale. Further experiments are needed to decide whetherquantitative differences between both data sets are physical.

In the temperature range 270-413 K. scaling behaviour isfound over three decades in frequency around the minima ofX<co) (Fig. 5). The master curve, however, does not followthe predictions of MCT (the asymptotic slope of the highfrequency wing should be smaller than 1/2, and it should besmaller than the negative slope of the low frequency limit).The scaling of MCT, if at all, holds in a considerably smallerfrequency window where scaling extends down to 243 K.The deviations at low frequencies suggest that the influenceof vibrational motion and possibly of bond-breakingprocesses is much stronger in network glass-formers than infragile materials.

Collective dynamics in mixtures of liquid Kbiind molten KhBr

Mixtures of simple liquid metals and their molten saltsare a very interesting class of liquids also from the point ofview of their atomic dynamics, as the interplay of optic andacoustic modes in the salt rich mixtures should lead to anextinction of acoustic modes in a well defined region ofmomentum transfers. In addition they offer the possibility tochange the interatomic interaction from a predominantlymetallic one on the metal rich side of the phase diagramto dominating ionic interaction at medium and high saltconcentrations. Measurements of the partial static structurefactors indicate that this transition from nearly free electronbehaviour to first influences from charge ordering startsto be observable already al a salt concentrationof 20 mole%, i.e. a concentration of only 10 mole'ft ofthe non-metallic ions.

The collective atomic dynamics in a mixture of 80% Rband 2()'7i RhBr was therefore studied at two differenttemperatures well above the liquidas of the mixture usingthe cold neutron TOP spectrometer IN6 with an energyof the incident neutrons of 4.7 meV |2|. In contrast to liquidRb. where collective excitations arc observed as maxima andshoulders in the dynamic structure factor S(Q,co), no suchstructure is evident in S(Q.<u) of the mixture at bothtemperatures, in complete agreement with earlierinvestigations of ionic melts. However, from the maxima ofthe longitudinal current-current correlation function J](Q,co)

/•"/.V. ."<: Reseated susceptibilities X"<taf(l)mm^Ximn- neutnm <i"l>)anil lii>lu Ihiniiiml scaltci'iiix diilti arc separated verticallytor clarity. Then1 is n wide scaling regime fur températuresfrom 270 In 413 K, extending over three decades.If lower temperatures (2J.1-263 КI are included, the scalingloses accuracy. e.\cept in a narrinr range of not morethan one décatie where i: can he filled with the matter junctiono/'MCT 1^ = 0.72).

C O L I E G

dispersions were obtained. In Fig. 6 the dispersion of liquidRb measured at 776K and obtained in (he same manner iscompared with the dispersions of the mixture measured at%6Ktmd lldOK.

The eolleetive dynamics of the atoms in a mixture of80 mole'/f liquid Rb with 20 moler/< molten RbBr as far asreflected in the maxima of the longitudinal currentcorrelation function lead to dispersion O)j(Q) with twominima in the region of momentum transfers investigated( 10 < Q < 30 nm"'). The position of the first at Q m m can besimply related to the principal peak al Qp in the staticstructure factor and even partly reflects its extension inQ-space. Tiie second minimum can be related to the secondmaximum in SMX(Q). It could therefore reflect the influenceof a change in the interatomic potential due to a change inthe screening mechanism after adding 20 mole'/< salt to theliquid metal. At the higher Q-values covered here, the freeparticle dispersion starts dominating the dispersion curve.

Local order in polyatomic and complex systems

Disordered systems of increasing complexity might stillpresent clearly identifiable local atomic arrangements.Although isotopic marking of a reference atom is a veryattractive and efficient method to access the local structurein such systems, many other approaches have beensuccessfully tried, giving insight into the loeal and mediumrange ordering. Combination of neutron and X-rayscattering, isomorphous, chemical and isotopic substitution,concentration dependence and temperature variation (liquid,undercooled liquid, glass) are used in the following studieswhich are characteristic examples of recent developments inthis field. Of course, this is also an area where furtherprogress is expected from the use of simulation to testvarious models of local and medium range order.

The total structure factor S(Q) of liquid LiNbO^ has beenobtained in a temperature range I623K > Т > 1490 К whichincludes undercooling |3j. From an analysis of the total paircorrelation function G(r) compared with the results of anX-ray scattering experiment as well as with the crystallinestructure, it has been possible to extract with precision thenearest neighbour distances г^ь-о ro-O- rl.i-O a n c ' t n e

corresponding coordination numbers. The Nb atoms remainoctahedrally coordinated up to one hundred degrees abovethe melting point. Interconnection of these octahedra bycorner-sharing and tightening of their arrangement via Liatoms with a small coordination number (nt j . o ~ 3). is alsoshown. At this local order level, no clear explanation isfound of the large density difference observed betweenliquid and solid LiNbO^.

A systematic investigation of liquid aluminium-transitionmetal alloys AIX()M->(). via isomorphous substitution, hasallowed us to find some indications of local icosahedralorder in the number-number structure factor S N N ofquasicrystal forming liquids, which were absent in otherliquids such as Al8()Ni2o- These indications are the existence

Rb80(RbBr)20 П 6 0 К

Rb80 (RbBr)20 966 К

0 5 10 15 20 25 30 35

Q[l/nm]

/•Vj?. ft: Dispersion relation (OjlQl tis obtained from lite m«.\iin</ inthe longitudinal current correlation functionJl(Q.co) = (irS(Q.O)l/Q2 for KbfdtlKblirh,, measured ut llfitlKlal.96(>K (hi and Kh measured tit 77ЛК Id, Compared with Kb oneclearly M'es the influence of the change in the interaction potentialt harder ami 2nd minimum tit 22 nm'1 > ami of the broader staticstructure factor on the dispersion curves of lite mixtures.

of a sharp first peak, the shape of the second peak, whichtends to form a double component peak at positions 1.7 Q|and 2 Q| (Q| being the first peak position) and the heightratio between the two first peaks close to the value of0.49 given by a Landau description of icosahedral order.The construction of Voronoï polyhedra in quasicrystalforming Alxolvh() liquids simulated by molecular dynamicshas confirmed this point of view, but the percentage of atoms

COLLEGE 6

with complete icosahedral symmetry is limited to a fewpercent. A siudv of the quasicrvstal forming liquid alloyAl7iPd|,|M|0 with M = Mnx(l;e( r)|. x was undertaken usingthe isomorphous substitution between Mn atoms and thea-FeCr mixture to confirm these results. The three partialsof a psetido-binarv representation of this system (AI and Pdbeing nearly equivalent) were obtained. The SN N itself wasdirectly measured for the ease y = 0.254. and itsuperimposes very well in reduced Q/QI coordinates on theSNN; of liquid AIX()Mib|) in which icosahedral order had beenseen b\ molecular dynamics |4 | (Fig. 7).

Numerous studies on vitreous solid electrolytes haveshown thai it is possible to increase significantly the ionicconductivity of these glasses by addition of a doping agent(e.g. AgXi in a weak ionic conductor (e.g. AgPO,). Severalmodels have been proposed lo describe ihe role of the addedhalidcs in the conductiv itv mechanism, but microscopicinvestigations were lacking. Since it is impossible lo extractthe full set of partial structure factors in such quaternaryatomic systems, an extensive set of determinations of Ihetotal structure factor have instead been undertaken, varyingthe nature of the halide (CI. Br. I). Ihe AgX concentrationand the C'l isotopic concentrai ion lor an AgC! mixture ( 'Ч.М.! S-Yl. "4M. !7(M). In all cases, the AgPO, structure isunaffected by the addition of AgX and the system can heconsidered as biphased. This is so true, thai the fraction ofAgPO, structure could be subtracted from the total structurefactor, giving access to the remaining AgX pattern.Moreover, the low О range of the structure (0.2 ' Q < 2 A"11is very sensitive to the nature of the X nucleus, its isolopieenrichment and lo the As;X concentration. A detailed sludv

0.00.5 1.0 1.5 2.0 2.5 3.0 3.5

Q/Q1IÀ-1)

114. 7: 'luiii/ \irnt Inn- lilt lor Slijl l/ir liquid Л1-; [I'd щ

/Mn,, ^jll i'1'ri,, -jrJ/uli'iiiiliiiHiHH iiin'd anil S^^lQi /iiiii-liiin JITfit/itul Al^,\ln^tl (hrnkcn ( iirvc) d\ it jiinclrtiii i>f (J/Q j .

done for five Agi concentrations shows that the prepeakobserved between I and 0.5 A has a position whichdecreases linearly versus the increasing volumic fractionin Agi suggesting a structure witi. nanoaggregales of Agiof increasing si/c embedded in a AgPO; matrix | 5 | .

As mode coupling theory of Ihe glass transition whichpredicts dynamical anomalies close to a critical temperatureT c located above Т„. is expecled to work better the more"fragile" the gl:-ss former. OTP (orlholerphenyl I wasconsidered lo be a proper model sy.siem vvilh relalivelysymmetrical and rigid molecules. This has led lo a series ofexperiments anil lo the proof of the existence of Tc at about2°0 К in this system. However, nothing was known aboutthe structure of OTP. although the structure factor S(Q) is ofthe utmost importance for ihe interpretation ol the dynamicalbehaviour as it is assumed that SlO) varies smoothly in Ihetemperature range where dynamical anomalies are observed.Studying Ihe temperature dependence of the static stuclurefactor of OTP we find that in contrast lo whai is known fromsimple liquids, the main peak of S(Q) is split into twomaxima which behave quite differently. Supercooling thesystem down lo T,,. the maximum at Q = 1.4 A'1 is not muchaffected, while the one at 1.9 A is significantly enhanced.This effect cannot be related lo a change of intramolecularconfigurations (the intramolecular .structure playing a role atlarger Q values and being apparently unaffected bytemperature variation) but is due lo the intermolccularsiriciiire. However, it varies smoothly, with no discontinuityaround T c . The physical origin of this temperaturedependence of S(Q) and its effect on the Q dependenceof the dynamics around Tc are being investigated |6 | .

The investigations into the structure and dynamics ofquasicryslals has continued with experiments using X-raysand neutrons (see Blue Box). In particular the anomalousX-ray diffraction close to the Pd K-edge has enabled thedetermination of the Pd partial structure factor. The resultscontradict the idea that atomic surfaces in the 6-dimensionalimages should be sharply faceted polyhedral objects. Recent(k oretical results suggest that the atomic surfaces mightnave fractal!) shaped borders.

Collective Kxcitations in 4He

The dynamic structure fuclor S(Q.co) in the collectiveexcitation regime of liquid 4He has been measured over awide range of temperature and wave-vector on IN6 | 7 | .The results summarised in l-'ig. cS show the variation of thescattering function with temperature at waveveclors of().4A"'(phonon). 1.2A"1 (maxon) and I.9A"1 (niton). Notethat for clarity the data used lo produce these figures havebeen smoothed so ihey provide only a qualitative illustrationof the t e m p e r a t u r e var ia t ion of the s c a t t e r i n g .The temperakii'c dependence in Ihe low Q region appearssimple. The scattering consists of a single, sharp peak whichbroadens with temperature: the mulliphonon component

C O L i E С Е 6

is relatively weak und well separated IVoin I he singleexcitation peak. The rate of broadening of the onc-phononpeak appears lo eliange at or near to the lambda transitiontemperature. 1\. but a well defined peak remains visible inthe normal fluid phase. At the maxon waveveetor. the lowtemperature scattering function is seen to consist of a sharppeak superimposed on a broad multiplionon background,which changes little with temperature. The sharp peakhowever, is seen to disappear at T^, suggesting that it is insome way a "signature" of the superfhiid phase, connectedwith the existence of the Bose condensale. The situation issimilar at the roton wavevcctor. Here the sharp peak is alsoseen to disappear at 'l\ and the scattering in the normal

Q = 1.9 A1

HK- "•' /•/£'"'<' I. Three dimensional representation of the

lenipenitiire dependence o/'S(Q,(i>)for 4Hc tit Q=0.4 A'1. 1.2 A'

ami I.<JA~'.

phase is peaked at an energy (of the order of 0.5 meV) lowerthan that of the sharp peak characteristic of the superHuid(0.74 meV at T=l.3 K). At all wavevectors the high-energytail of S(Q,co) is observed to change very little withtemperature. In general the variation of S(Q,(0)with temperature is very marked in the superfluid phase butalmost non-existent in the normal fluid, particularly at highQ. The overall wavevector dependent température variationof the excitation spectrum provides support for ivcenltheories in which the linear dispersion part of the spectrum isseen as consisting mainly of а /его sound mode, similar tothat observed in Fermi liquids, while the maxon and rotonexcitations arise from the excitation of a single c|iiasiparlicle.The single particle excitations are coupled to the densityfluctuations by the presence of a non-/ero Bose condensate.They thus establish the connection between the Bose brokensymmetry and the sharp one-phonon excitations seen in thesuperfluid phase.

The surface dynamics has also been measured fromliquid 4Hc films adsorbed onto graphite (see Blue Boxcollege 2). The data show evidence of layer plumons thatpropagate within the liquid layer in good agreement withtheory.

Investigation (if rough interlaces in multilayersby specular and non-specular X-ray reflection

Interface and surface roughness is of crucial importancein thin layer physics and is a decisive factor for theirtechnological applicability. It strongly influences thephysical properties of multilayers such as the quantumefficiency of semiconductor superlattices and the magneticcoupling in magnetic multilayers.

X-ray scattering methods are non destructive and allow astatistical description of interlaces. The point properties ofthe interfaces (r.m.s. roughness) can be investigated byspecular X-ray reflection (SXR). Using non-specular X-rayreflection (NSXR) the in-plane correlation (lateralcorrelation length, fractal dimension of the interlace) can bedetermined.

Both X-ray methods have recently been usedsuccessfully to study single surfaces. Yet NSXR has rarelybeen applied to multilayers, as important features present inthe experimental data obtained from multilayers could not beexplained theoretically. The previous theoretical descriptiononly included the effect of specular surface reflectionwithout laking into account the specular reflection at theinterfaces.

Describing the specular interface reflection within thefull dynamical theory, a formalism based on aDistorled-Wavc-Born-Approxiinalion (DWBA) wasdeveloped, which overcomes the problems of previous work[8]. Considering now the specular reflection from the surface

COLLEGE 6

as well us from Ihe interfaces we are able to simulatethe coherent and incoherent cross sections of diffusescattering from multilayers with rough interfaces including:

1) the interaction between specular interface reflectionand diffuse scattering (generating Bragg-like peaks in theNon-Specular X-Ray Reflection).

2) the effect of resonant diffuse scattering (RDS) in\enical partial correlated superlattices. (Thus we candistinguish between vertical non-correlated and cot jlatedinterface roughness),

3) the contribution of diffuse scattering in transmissiongeometry, observable above the surface only due toUmweganregung caused by specular interface reflection.

We demonstrate the effect of partially vertical correlatedinterface roughness for the example of a GaAs/AIAs-superlalticein h'ig. У showing (lie calculated reciprocal space mappingof the primary diffuse scattering in tlie kinemalicalapproximation (Fig. 9a) and in a DWBA, consideringthe reflection at Ihe surface and the refraction withinthe layers (Fig. % ) .

In the kinematical approach the diffuse scatteredintensity of partial vertical correlated interfaces isconcentrated in strips of resonant diffuse scattering (RDS),

being parallel to the sample surface and going throughthe lattice points of the one dimensional reciprocal latticeof (he multilayer. Limited hy the geomelrical hori/on of thesample the measured intensity would be restricted betweenthe Ewald spheres f| and fi which mark where the incidentor exit angles become /его.

Considering simultaneous specular reflecting fromthe sample surface and the refraction of X-rays in the layersin the calculation gives rise to:

I ) a bending of the RDS sheets due to the X-ray refraction,

2) an enhancement of intensity at the critical angleof total external reflection for the incident or scattered beam,creating the so called Yoneda wings.

The specular interface reflection causes additional .sharpresonances in the distribution of diffusely scattered intensity.if the incident or the scattered beam fulfills the Braggcondition of the superlattice (Bragg-like peaks). Theirpositions in the reciprocal space are marked by crosses inFig. %. The occurrence of Ihe Bragg-like peaks i.s a puredynamical effect of multiple scattering and can beunderstood by the concept of Umweganregung |9|. They aredescribed within an extended DWBA as can be seenin Fig. 10 which shows the experimental and the fittedNSXR rocking scans of a GaAs/AIAs superlattice.

0.05 -

" * N * ^ \ " " ~ ^ .»'"* Ï"

N V v ^

11 ' • * ' it

^Лл-.'Л".Т1::^х:Л^ w

-0.002 0.000Q/QlfA-1]

0.00| (b)i i i i i i

-0.002 0.000 0.002

/•'/#. 4: Non-specular intensity dislrilnilion in the reci/irocei/ /itaite for lite case of vertical partial correlated Interface ти.ц/техл:a) calculation within the first Horn approximation without X-ray refractionh) calculation within a DWHA taking into account the specular X-ray reflection fioin the surface mid refraction in the layers.The iloltetl line s represent the Ewalel i ircles f / ?. The NSXR intensity in the inacct"<sihle regions is denoted hy dashed lines. Crosses denotethe positions of the Нгацх-like peaks, neglected in this approximation hut < onsiaeml in Fig. Id

COLLEGE 6

The bro;nl central hump arises from resonant i l i l ïuscscattering (I\1)S) anil gives evidence of the existence ofvertical correlation hclueen the rough iiiicrl'accs. In addition.l\\o Yoneda \sings ma) he seen on each siile of the centralpeak \ \ i lh several Uragg-like peaks between them, welldescribed h\ the theorv.

002 -0.001 0.000 +0.001 0.002

1чц. /II: ч) м «/is (/loi'ii/sj iiif4\iin;l tiltnix l/ir /rii/'rrlor/cs .voi'n.i;t/iiimt;/! lilt1 jnl t/itif till «/it/ I/if 4lh Нгчкк /><'<Ж * l/i»'' 14».Line (4 1 h \liillftl n/>Hunl\ In- ii /iiflni- />/' 10. '/'lie /lilt", </n' llir />r.slllici4'fiii;il /Us /пап niir f\'i'ntlftl 1)\\'НЛ. \\-liit h ,lf\rril>r\ (i/so

-0.01 0.01

energy (meV)

/•'1.4. 11: Qiittui'luMH iii'iilriin scd/lc/v'ii.i,1 s/)c( ira /ni'ii Ni-^ ^irvsM/ in uni' s/xn'/iV ( iy\itil nriciiliiliiiii ni Q I'd/lies o/ till0.41 Л I tiinl ihi I.N2 Л '. У= N0(1 С.

The theoretical Irealiiient also allows the description of

specular and non-specular rellection of neutrons hy rough

multilayers.

Self-diffusion in intcrmctullits

The Ni diffusion mechanism in the inlernielallic alloysNi.S h ami Ni;.Sb has hcen elucidated by QNS iiieasuremenlson single crystals, performed on INK). In the BS phase NiSbthe Ni atoms perform jumps between the regular Ni sites(octahedral interstices of the hep lattice made up hy the Sbatomsi and the double tetrahedral interstices (DTI), whichare very scarcely populated. The experiments on the DO)phase Ni tSh |l()| necessitated a more sophisticated sampleeiniromnenl. as the alloy studied is stable above 5M1" Сonly. Therefore, the single crystals had to he grown in aspecial iibsilu growth furnace, oriented on INX and thentransported to INK) without cooling down the furnace. Dueto the shutdovsn of the I L L reactor, these results arc-preliminary, hut the data seem to agree with a very simplejump model: nearest-neighbour jumps of the Ni atomsbetween the two Ni suhlaitices. The same mechanism hadbeen found to he operative in the DO, phase Fe^Si byMossbauer speciroscopy. The Ni dilfusivity in Ni^Sh is veryhigh, leading to very pronounced quasieiaslic broadeninge\en at moderate temperatures (Fig. I I )and facilitating theseparation of the QNS signal into two Lorent/ians.

The systems Ni^Sb and l-'e^Si have also been investigated by

neutron diffraction on DMC at the PS I 11 11 as a function of

the alloy concentration and temperature. It has been shown

that deviations from stoichiomelry are compensated in very

different ways in the two alloys of the same structure:

whereas in F'e^Si antistructure atoms of Fe on Si si'e'- are

formed. Ni^Sh compensates the excess of Sh by vacancies

on the Ni sublatlices.

The phonon dispersion of h'e^Si alloys (F'ig. 12) has been

studied on I-T at LLH [ I 2 | in order to decide if the fast Fe

diffusion in these alloys is related to soft modes. Although

there are low-energetic modes and a very distinct softening

of the lattice at high temperatures, there is almost no

dependence of the phonon energy on the alloy concentration.

Mosshauer studies have indicated that the Ke difl'usivily in

F'e^Si is strongly dependent on the alloy concentration, thus

the observed fast diffusion cannot be explained by lattice

dynamical effects alone.

High temperature lattice dynamics and diffusion

in niobium

Recently a close relation was established betweenparticular low energy phonons and high diffusioncoefficients in cubic metals. Due to the temperature (T)dependence of phonons in metals the diffusion barriers are

Coi iEGE 6

no longer constants, but sensitively depend on T.For instance in hcc-/r phonons stitïen with increasing Т andconsequently the migration barrier for vacancy diffusionincreases with T. Cr shows the opposite behaviour. Heremigration barriers are high at low T and no anomalously lowphonons are found, whereas migration barrier and phononsare low at high T. The d-electron density is supposed to bethe control parameter. Nb with 3d electrons lies between Zrand Cr and therefore should show an intermediate behaviour.

To prove this the phonon dispersion has been measuredat 293K. 77.Ж. I773K and 222.Ж (measurements at IN3ILL, IT Saclay. DNI Siloe. HB1 Petten) [ I3|. Fig. 13 showsa summary of till dispersion measurements which arerepresented by the results of Born-von-Karman fits.A detailed inspection of this figure shows that(except 1.0.5(1 10)) Brillouin /one boundary phononsdecrease continuously with T. Two important exceptions

0.5 0 1.0 0.5

reduced wavevector

o>ФсФ

reduced wavevector

/•'«,'. 12: Л i/elt/il i>f the phiinim dispersion* «/'/•

tind l-'CffifSi^/i

/•'/,<,'. 13: Kiim-viHi-KiiriiKiii /ï/.v i>J plionuii ilibpenwn in Nhai - 2WK. - - - 7 7 Ж, --- 1 77 Ж ami --- 222 J К.

from this normal decrease have to be mentioned: theL2/3(l 1 1) phonon increases from 293 К to 773K. stays at aplateau up to 1773 К and decreases above I773K. The shearconstant C' qualitatively shows the same T dependence.

Due to the dominant role of these low energy phononsin the calculation of the migration barrier

H M = i thG°=Mo)2

(where G() is the static lattice Green's function, а аgeometrical factor, a the lattice parameter, Z(co) the density ofstates and M the mass) H shows a similar variation with T.

We conclude with the following picture of the diffusionanomalies in the group 4 to 6 metals: from bcc-Zr throughNb to Cr the d-electron density increases, the motionof 11111 nearest neighbour rows in these metals is more andmore hindered and consequently diffusivities decrease. Thiseffect i.s particularly pronounced at low T, whereas close tothe melting point diffusivities normalise to a common value.

Hydrogen in Metals

The rare-earth dihydrides p-RH-,+x form an fee structurein which, ideally for x=(), the hydrogen occupies all ofthe tetrahedral (t) sites. In the superstoichiometric region.0 < x < xm.M. the excess hydrogen occupies the octahedral(o) sites. Further addition of hydrogen above xm a x leads tothe precipitation of the hexagonal y-RH, phase. In thedihydride phase the excess hydrogen gives rise toconcentration dependent changes in the electronic structurewhich manifest themselves in metal-semiconductortransitions related to ordering of the octahedral H sublattiee.

COLLEGE 6

In particular р-ТЪЬЬ+х has been shown lo possessseveral x-dependenl magnetic ordering phases below ~4() K.At higher temperatures (150-200 K), neutron diffractionstudies on T b D 2 + x (0 < x < 0.25) have shown that theoctahedral H orders for x > 0.1 into a Ni^Mo structure inwhich 3 vacant (420) planes are followed by an occupiedplane, a structure which is stoichiometric at TbD215 114).

The concentration and temperature dependence of theordering phenomena have been followed using neutrondiffraction and inelastic neutron scattering at NIST and PSI.Figure 14 shows the concentration dependence of the localmode due to octahedral site H in TbH2+x measured at NISTusing a Be/PG filter spectrometer. It is easy to distiguish thevibrational spectrum arising from H occupying I and о sitesin these systems since the former occurs in the region near120 meV while the latter is observed near 80 mcV. At lowconcentration and low temperature a single relatively sharpvibration feature is observed centred at 80.5 meV due toisolated H in a cubic environment. As the concentration is

Huang scattering from YD 0.05

"S= >8с0

э0)с

• &Î6

г „S

; и• » Q

- ч 9

г ? |« *о 5

1 1| $ „ о

- , , , , , , , , , , , !

3.75 3.8 3.85 3.9 3.95 4 4.05 4.14.15

/•'/Я. /5: Comparison of thé Huunx scatlerinx in thé (ПО) (Ш)1)plane of Yl)fi/tf(o) Mid pure Y( + ). The scans were taken in the j -£,—<!;, 4+^1 direction about the (004) reflenion.

70 80 90energy loss (mev)

Fig. 14: The vihrational density of states due to H on octahedralsites in /i-TbHz+xfor different values ofx. The continuous linesare guides to the eye.

increased the vibrational spectrum splits giving rise,at x=0.25, to a clearly bimodal structure with a higherenergy peak at 83.1 meV having twice the intensity of thelower energy peak centred at 76.7 meV. A similar transitionis seen as a function of temperature and can be clearlyrelated to the ordering of octahedral H. In the fully orderedNi^Mo structure, each о site H is an intersecting member ofidentical chains (-H-Tb-)n in the |100| and [001] directionsand a (-H-Tb-v-Tb-)n chain in the [010] direction where vrepresents a vacancy in the H sublattice. Thus the doublydegenerate high energy mode corresponds lo vibrations inthe [I00| and |0()1] directions whereas the low energysinglet is due to vibrations in the |010] direction. The resultsshow the importance of the H-H interactions in thesesystems which extend to at least second nearest neighbourdistances 115|.

In a complementary study on the hexagonal a-R(H/D)x

systems the neutron Huang scattering due to isolated Datoms has been measured in YD^os in collaboration with K.Ai/awa at JAERI 116). The results shown in Fig. 15 indicatestrongly asymmetric Huang scattering in particulardirections which will enable the distortion field surroundingan isolated D atom to be determined and compared withongoing nSR measurements on these systems.

Secretary: Ian Anderson

References

11 ] B.Frick, D.Richter, S.Trevino, Physica A 201 (1993) 88-94.

|2] P. Chieux, J. Dupuy-Philon, J-F. Fal, C. Morkeland J-B. Suck, J. Phy.s.: Condensed Matler6 (1994) 1.

|3] P. Andonov, P. Chieux and S. Kimura,J. Phys.: Condens. Matter 5 (1993) 4865.

С О /. 1 Е С Е 6

Н| M. Muret. J.M. Dubois. P. Chieux. .1. Non-Crvsl.Solids 156-158(149.1)418.

| ? | C. Rousseloi, R. Mercier, J.P. Malugani. M. Tache/and P. Chieux. .1. Plnsique IV, Colloque 2 ( 1942) 214:C. Rousselot. M. Tache/, J.P. Malugani. R. Mercierand P. Chieux. ,1. Plnsique IV. Colloque 2 ( 1992) 2l I.

|61 K. Barisch. H. Bertugnolli. P. Chieux, A. Davidand H. Silleseu. Chem, Phys. 169 ( 1993) 373.

|7 | K.H. Andersen. W.G. Stirling, R. Scherm.A. Sumaull. G. Fak, H. Godfrin and A.J. Diunoux.J. Phys. С in press.

| 8 | G.T. Baunihacli, U. Pietsch, V. Holy,M. Gailhanoui Physica В ( 199.3), in press

|9 | V. Holy, G.T. Buumbach, Phys. Rev. B 1993.in press.

11()| B. Sepiol. O.G. Randl, C. Karner. A. Helming,and Ci. Vogl, J. Phys.: Cond. Mailer, submitted.

1111 O.G. Randl. G. Vogl. B. Sepiol. W. Pelry.P. Teivieff. W. Biihrer;mcl V. Allorfor.

LNS Progress Report 199.3.

112| O.G. Rundl. W. Petry. G. Vogl, B. Hennion.B. Sepiol and E. Nembuch, to be published.

1131 F. GiiiholT. B. Hennion, C. Her/.ig.W. Pelry H.R., Schober and J. Trampenau.J. Phys.: Cond. Mutter, in press.

114| G. André. О. Blashko. W. Schw.ir/. J.N. Duouand P. Vajdu, Phys. Rev B46. 8644 ( 1992).

115| T.J. Udovic. J.J. Rush and I.S. Anderson.

to be published.

116] C.M.E. Zcyen. K. Ai/uwa and I.S. Andersonto be published.

Report on the Workshop"Dynamics of Disordered Materials II"held at the Institut Laue-Langevin,22-24 March, 1993.

Following the success of the first workshop on"Dynamics of Disordered Materials" held in September1988, a second meeting took place in Grenoble duringMarch 1993 with the objective of reviewing the considerableprogress made. The meeting was jointly organi/ed by theInstitut fur Festkorperforschung of the Forschungs/entrumJiilich and the Institut Laue-Langcvin in Grenoble.The proceedings of the workshop will be published at theend of 1993 as a special issue of Physica A and will contain13 review articles and 44 contributed papers, in both theoryand experiments on disordered materials, addressing inparticular the dynamics of glasses and the glass transition.

The main thrust of the workshop was directed towards anexperimental evaluation of the mode coupling theory of theglass transition (M(T). In particular, scattering methodssuch us dynamic light scattering and neutron scatteringe4periments as well as computer simulations were presentedin which the undercooled liquid strongly supports modecoupling predictions. Materials as different as polymers,molecular and ionic liquids, colloidal systems and liquidmetals were investigated. While this general agreementseems lo hold Cor fragile glasses, strong glasses like networkglasses seem to be less well accounted for.

At lower temperatures in the close proximity of the glasstransition the situation is less clear, Besides the highfrequency "mode coupling" [i-relaxation a slow relaxationintrinsically coupled to the (/.-relaxation is observedmicroscopically which cannot easily be interpreted by MCT.Another very important issue in this low temperature regimerelates to the question ol'cooperalivity close lo Tj,. Importantnew developments seem to give indirect evidence for theexistence of such a cooperativity length which increasestowards Tj,. Furthermore, light scattering experiments haveestablished the presence of large scale density fluctuationsreaching into the micron regime.

Another important topic concerns the soft phonons inglasses. These were originally observed as a so-called Bosonpeak in Raman scattering and later on characterised in detailby inelastic neutron scattering. These soft phonons are anintrinsic ingredient of the glassy state and relate lo structuralinstabilities. Considerable progress has been reported in thisfield, leading towards a unified understanding of these soilvibrations, including the low temperature two-leveltunnelling excitations.

Besides this main theme, a series of other aspectsof glasses were illuminated stretching from the dynamicsof melglasses to biological systems dealing with phenomenasuch as the effect of confined geometries on water dynamics,the polymerisation transition in sulphur or the concentrationfluctuations in polymer blends.

The following invited lecturers presented a wide rangeof re\iew talks covering all aspects of the workshop:

• A.J. Dianoux (Institut Laue-Langevin.Grenoble. France) "Neutron scattering by disorderedmaterials: an introduction"

• M. Fuchs (T.U. Miinchen. Garching. Germany)"«-Peak shapes discussed within ihe mode coupling theory"

• H.R. .Schober (IFF. .liilich. Germany)"Soft phonons in glasses"

• .1. Colmenero (U. del Pais Vasco. San Sebastian. Spain)"Dynamics of the «-relaxation in glass-forming polymers.Study by neutron scattering and relaxation techniques"

• R. Zorn (IFF. Jiilich. Germany) "Neutron scatteringexperiments on the glass transition of polymers"

COLLEGE 6

• К. Kawasaki (Kyushu I'niversii). Fukiiokti. Japan)"Relaxation and growth of concentration fluctuations

in polymer blonds"

• J.-P. Hanson (HNS. I.von. l-'raneoi "Kinetic glasstransition in liquids and colloidal suspensions;what do we learn from molecular dynamics sinuilations '.'"

• K.W. Fischer (MPI l'iir Polymerforschung.Main/, Germany) "Light scattering and dielectric studieson glass forming liquids"

• II'/.. Cummins (City College-CUNY. New York, USA)"Light scattering speetroscopy of the liquid-glass transition:Comparison with idealised and extended mode couplingtheory predictions"

• F. I-'ujiirii ILL Main/, Germany) "Signatures of the glasstransition m van dor Waals liquids seen by neutrons anil NMR"

• H. Rtissler (Freie Università'l, Berlin. Cîermany)"Dynamical phase transition in supercooled simpleliquids and polymers - a NMR approach"

• P.N. Pusey (U. of Edinburgh. U.K.)"The dynamics of amorphous stales of colloidal systems"

• 1". Parak (U. Main/. Germany I "Protein dynamics"

• M. Descamps (U. Lille I. Villeneuve d'Ascq. France)"Orientational and structural relaxation in a glassy crysial"

Compared to the last workshop a richness of verydetailed ne\\ quantitative results evolved facilitating a morequantitative comparison with model predictions. However,the complexity and in particular (he enormous dynamicrange accompanied by the missing translational symmetrystill poses ;i tremendous challenge, which in the futureshould be mot by concentrated efforts using as manyexperimental methods as possible on the same materials.Nevertheless, we hope that the proceedings of this workshopdescribing the present day situation will stimulate furtherwork in this very interesting and exciting domain.

The organi/.crs thank the contributors for preparing theirmanuscripts promptly. We express our gratitude to theInstitut I.aue-Langeviri and the Forsclnmgs/eiilrum Jiilichfor their financial assistance. We would also like toacknowledge J.P. Hanson and H.7.. Cummins for theircritical summary and are grateful to B. Major and his staffwho helped to organi/e the workshop, and to Mrs. BrigitteAubert as the workshop secretary.

Grenoble. Munchcn, Jiilich

Albert-José Diaiioux.Winfried Petry. Dieter Richter

Precise experimental determination of the structureof noble fluids: two- and many-body contributions

I-'abrizio Barocchi, Pierre Chicux, Rcnato Magli

The structure of a fluid (liquid or gas) is consideredto be known when the spatial distribution of the atomsin the system, ul a precise lime t, is known. In principlethis can be accomplished only with the knowledge of allthe irreducible spatial correlation functions involved inthe system. However, theory and experiments, at present,can deal only with the simplest of these functions, i.e.the so called pair correlation function g(r|i).

Experiments give information on g(r|i) by means ofmeasurements of the static structure factor S(k) which isrelated to the spatial Fourier transform of the paircorrelation function as follows 11 ]:

S(k) = 1 + n g(r12) -1 exp(- ik. r12)dr12(I)

where n is the number density. S(k) can be measuredby either X-ray or neutron diffraction, k is thewavevcctor transfer in the diffraction experiment and Г|тis the distance vector between two atoms.

In the field of fluid structural studies the followingstatements about S(k) have often been accepted. ( 1 ) Thebehaviour of S(k) in dense fluids is dominated by strongmicroscopic repulsive forces present at short range, andonly very small details of S(k) are connected to thepeculiar properties of §(г ]2). (2) S(k) cannot be measuredin a wide enough k-range and with an accuracy no betterthan a few parts per hundred. As a consequence S(k) datain fluids are not very useful for detailed studies of g(r|i).

We will show that by means of a neutrondiffractometer such as D4, S(k) can be obtained with aprecision of a few parts per thousand |2 ] . Thereforeprecise tests of existing modern integral equationtheories for g(ri) and investigations of the nature ofmicroscopic interactions in fluids can be performed [3|.

For studying structural properties in simple fluids,it is convenient to define the direct correlation functionс(Г|т) which is given by the Orstein-Zernike relation [11:

g(ri2) -1 = c(r12) + njd 3 r' c(r') [g|r ia - r'| ) -1 ](2)

From equations (I) and (2) it is easy to see that forthe Fourier transform c(k) of c(i'|->) the following relationholds:

С О L L Е G E 6

When the density of the fluid is sufficiently low,g(r) can be expanded with respect to the density n, this isthe so called "virial expansion" and is given by

g0(rp) + ngi(rp) + O(n2) (4)

g()(r,2) = exp|- PU,( 1, 2)] with p = l/kBT

9i(r12) = g f ( r i 2 ) + g f W

9 1 Via) indicates the part of g|(r|2) that depends onlyon the two-body potential while gf'Uis) depends also onthe three-body potential and only the first two terms inequation (4) arc retained.

From equations (I) , (3) and (4), S(k) and c(k)can also be expanded. In particular we write.

c0(k) = 90(1-12) -1i exp(-ik- ri2)dr1 2(8)

) = cf'(k)+ cf>(k) (9)

As a consequence it is seen that a measurement of thedensity behaviour of S(k) at low enough density givesaccess to the pair and three-body terms of c(k). The pairterm c0(k) is directly related to the pair potential U2(r)and this last function can therefore simply be derived bymeans of a Fourier inversion of an experimental c0(k).Moreover, once the pair potential is known ameasurement of C|(k) also gives the possibility ofderiving information on the three-body potentialu3( 1,2,3).

For the case of dense fluids another approach isnecessary. We may use the modified hypernetted chainexpression (MHNC) to relate the interaction potentials tog(r), which writes [4],

g(r,2) = exp [- pu2(r,2) g(r,2) - 1 - c(r12) + C(r,2) + E(r,2)]

C(r ] 2) is the dressed three-particle vertex:

C(r1 2) = n j d 3 r3 g(r1 3) д(г2 3) {exp f - риэ(Г| , Г| , г, )] -

(П)and E(r i 2) is the so called bridge function.

With some initial estimate of E(r ) 2) and a model forboth the pair and three-body potentials, the MHNCequation can be solved iteratively and the calculatedg(rj2) compared with the experimental one to checkthe validity of the model potentials and the precisionof the integral equation as well.

Recent measurements of the static structure factor influid noble gas have been performed with a very highstatistical accuracy, even at low gas density. Rigorousdata analysis procedure has made it possible to reach afinal precision in S(k) sufficient for the densityexpansion studies of c(k).

Argon at low density

S(k) was measured in 36Ar at Т = 140 К and at fourdensities, i.e. n = 0.902, 1.399, 1.900, 2.393 at.nm"3

(the density of the liquid at the triple point isn = 21.15 at.nm"'1'. Fig. i shows as an example theexperimental c(k), for one thermodynamic state obtainedon the D4 instrument [2].

Figure 2 shows the experimental density behaviour ofc(k) | 5 | . The linearity predicted by the virial expansionof equation (7) for u low-density gas is very well

- 0.20E

0 20 40 60

k(nrrv')

80 100

Fig. I: c(k) at n = 0.9 al/mir1 and Т = 140 К for MAr.

Fig. 2: Experimental c(k) as a function of density at various k-values (symbols, from top to bottom : k = 1.35, 1.82, 2.31, 2.80and 3.34 nnf1' respectively) and weighted linear fits to the data(continuous lines) for }6Ar. 15].

COL L EGE 6

represented by the experimental results, therefore the pairterm c0(k) and the three-body term C|(k) can be derivedfrom a linear least squares fit of the experimental densitybehaviour of c(k) at all the measured k-values.

In Fig. 3, the experimental determination of c0(k) iscompared to a theoretical calculation based on equation(5) using the pair potentials of Aziz [7] or Barker [8](difference between these potentials cannot bedistinguished on the scale of this figure).

In Fig. 4, the virial coefficient C|(k) is compared totheoretical predictions using only the Barker FisherWatts (BFW) pair potential [8] or including also theAxilrod-Teller-Muto (ATM) three body potential forArgon 19,10] or its modification 111 ].

We observe that the agreement between calculationand experiment is very good except at low k values,where the experimental c0(k) is systematically less thanthe predicted one, the reverse being the case for C|(k).These deviations are significantly larger than theestimated errors (error bars given in fig. 4 are correlatedto the various instrumental settings).

It is possible to Fourier transform the experimentalc0(k) to determine by means of equation (5) anexperimental pair potential u2( 1,2). Extrapolation of theexperimental data to k = 0 and truncation at high k affectc0(r) only at a maximum of 1 % in the region of the peak;quantum corrections to c0(r) are of the same level [12].It is worth noticing here that the measurement of the zerodensity limit of c(k), i.e. c0(k) gives a unique methodof determining the microscopic pair potential in classicalsystems by means of a direct inversion of theexperimental data.

The experimental potential given in Fig. 5 agreesvery well at long range with the literature value, howeversome disagreement is found in the well where

-0.005

-0.010

-0.015

-0.020,

_n nos

liliiiiJ-ifffl

.1. ,1 ..II, l -J-r^^

lllltJ :-1ïïî '.ifrlllll 1'

10 2 4 6 8 10 12 14 16 18

k(nm')

/•7,1». 4: c/(k)frt»n linear density-expansion ofc(k) {error ban)and ax calculated from Barker-Fisher- Watts pair potentialalone (continuous line) or including the Axilroti-Teller three-body potential (doited tine) or its modification by Loubeyre(dashed line). The k = 0 value (square) lias been calculated bymeans of the equation of state for Argon /6/,

• \ Х > ^ " " " "

V, j r

\,/).30 0.4 0.5 0.6 0.7

Fig. S: The pair potential from this work (dots) is comparedto the one taken from the literature [7] (сипе) for J6Ar.

25 50k(nm')

75 100

Fig. 3: C0(k)from extrapolation ofc(k) ton = 0 (dots)and calculated from pair potentials taken from the literature(curve) for ~ Ar. Typical error bars are shown.

the experimental well depth is e/kB = 134 ± 3 К andthe value of r at which the potential equals zero isa = 0.338 ± 0.001 nm while the Barker potential givese/kB = 140.2 К and о = 0.336 nm.

Krypton at high density

S(k) (3.6 < k < 16.2 mrf1) of dense fluid krypton, hasbeen measured |13] on D4 at seven differentthermodynamic states from the triple point to around thecritical temperature (T values ranging from 130 К to 200 K,and densities from 11.9 to 17 nm"3). In order to study therelation beween S(k) and the microscopic interactionpotential, these experimental data have been compared(see figure 6) to a theoretical calculation performed by

C O M EG E 6

iteratively solving the MHNC integral equation (10).Two models which are considered accurate (Aziz [7] andBarker [14]) have been chosen lor the interaction pairpotential entering MHNC. The calculation has beenextended to take into account the presence of three bodyinteractions using Axilrod-Teller-Muto (ATM).Theoretical and experimental S(k) values are notdistinguishable at the scale of the figure [13].

In order to magnify the effects, we consider thedeviation AS(k) = Sexp(k) - SM H N C(k). We observe that itremains below 0.02 to 0.05 depending on density andthat for k > 50 nm'1 it falls within the noise of theexperiment. The larger deviations (~ 0.05) obtained atthe higher density (T = 130 K) are in great part due to theinadequacy of the MHNC equation. The calculated

modifications due to three body effects are weak andapparent only at low k values. Rg. 7 displays AS(k) foran intermediate density and temperature, it also displaysthe deviation observed for the Lennard-Jones potentialwhich gives particularly poor results in the region of themain maximum of S(k). [5].

When the comparison is performed in the r-spacein terms of g(r) it is again necessary to plotAg(r,2) = gexp(ri2> - §MHNdri2) i n o r c l e r l o observe thesmall deviation remaining between theory andexperiment (see Fig. 8). which gives an indicationof additional forces of many body character repulsiveat short range and attractive at larger distances.

и' 1.0

0.02.5

20 40 60k[nm']

80 0.7

Fig, 6: S(k) over the k < 100 nm range of measurementat (a) = I99K,n = 1 1.86 nm3, (b) Т = 169 К, п = 14.57 nm3,(с) Т = 130 К, п = 16.83 run . The continuous curve isthe result of the triplet MHNC equation with the Aziz pairinteraction plus the three-body ATM term. Value atk = 0is from the compressibility data.

_ 0.15

- 0 . 1 0

1 0.05•л

Ц о<"-0.05иg -0.103 -0.15

-0.200 10 20 30 40 50

k(nm ')

Fig. 7: The difference AS(k) = S^k) - SMIMC(k)for the ,4:i:pair interaction with (continuous curve) and without the A TMthree-body term (crosses) and for the Lennard-Jonesinteraction (dotted curve) for Kr at Т = 169 Кand /i = 14.57 nm''.

•0.1

Fig. 8: Difference Ag(r) = gex^r) - дмнмйМ . дмннйЮ iscomputed for the Aziz pair interaction including (continuouscurve) or not (dotted curve) the ATM three-body interactionand also for the Lennard-Jones interaction (dot-dashed curve).

COLLEGE 6

Finally the measurements of S(k) at closely (1 to 6 %variation) spaced densities [ I 5 | , give access to theisothermal density derivative dS(k)/dn. This quantity isimportant because it contains information on 3 bodycorrelations and also because it is very sensitive to theinteraction potential. We show, figure 9, the comparisonbetween experimental and theoretical results at k values< 40 nm i.e. where the pressure effects are noticeable.Again the accurate potentials of Barker and Аг1г are ingood agreement with experiment and the three-bodycontributions important only at very low k-values.

-0.0210 20

k[nm-'i30 40

Fig. 9: SS(k)/8n far (lie Aziz pair interaction with (continuouscurve) and without the ATM three-body term (dashed curve),for the LJ interaction (dot-dashed curve), and fromexperimental data (•) at (a) T = 199 К, (h) T = 169 К,(с) Т = 130 К. Value at k = 0 is from the compressibility data.

We can conclude that a very precise (within a fewparts per thousand) determination of S(k), over a large krange can now be performed and the comparison withtheory gives the opportunity to investigate in detail ourknowledge of the structure of fluids and the connectionbetween the microscopic interaction and the spacecorrelation of the atoms in the system.

References

111 J.P. Hansen, I.R. McDonald, Theoryof Simple Liquids (London: Academic ) 1976.

12J H. Fredrikze, J.B. Van Trient, A.A. van Well,R. Magli, P. Chieux and F. Barocchi,Phys. Rev. Lett. 62, 2612 (1989).

[ 31 L. Reatto and M. Tau, J. Chem. Phys. 86,

6174(1987).

14| L. Reatto and M. Tau, J. Phys.:Condens. Matter 4, 1, 1992.

[5] F. Barocchi. P. Chieux, R. Magli, J. Phys.:

Condens. Matter, В 49 (1993).

[6] R.B. Stewart et al. ( 1982). Proc. 8th Symp.Thermal Physical Properties, éd. J.V. Sengers

(N.Y.: Amer. Soc. mech. Eng.).

[7] R. A. Aziz and M.J. Slaman, Mol. Phys. 58,679(1986).

[81 J.A. Barker, R. A. Fisher and R.O. Watts,

Mol. Phys. 21, 657(1971).

[9] B.M. Axilrod and E. Teller, J. Chem. Phys. 11,299(1943).

[10] J. Muto, Proc. Phys. Mathem. Soc. Japan, 17,

629(1943).

[11] P. Loubeyre, Phys. Rev. Lett. 58, 1857 ( 1987).

[12] F. Barocchi, M. Neumann and M. Zoppi,Phys. Rev. A 36, 2440 (1987).

[13] F. Barocchi, P. Chieux, R. Magli, L. Reattoand M. Tau. J. Phys.: Condens. Matter, 5,4299(1993).

[14] J.A. Barker, R.O. Watts, J.K. Lee, T.P. Shaferand Y.T. Lee, J. Chem. Phys. 61, 308 (1974).

[15] F. Barocchi, P. Chieux, R. Magli, L. Reattoand M. Tau, Phys. Rev. Lett. 70, 947 (1993).

COi i EG E 6

Structure and properties of (|ii;isicrystals

Ch. Janot

Atomic order in solids is best defined in terms of theFourier transform of the mass density. In an ordinarycrvstal, this transform can be written us a series:

(1)in which:

G = ha i + ka 2 + la a(2)

are vectors of the reciprocal lattice whose basisvectors arc the a,' (h. k, I are integers, Miller indices).

The same definition still holds for quusicrystalsexcept that more than three basis vectors a ,' are requiredlo span the reciprocal space. For instance, in the case oficosahedral quasierystals. six basis vectors must beconsidered, so that:

12 atoms and finally an icosidodecahedron of 30 atoms.The external diameter of a PM1 is a little less than 10 Aand the centre distance of two nearest neighbour PM1 isabout 20 À. A section of the AlPdMn structure ispresented in Fij;. 2: rings of atoms are visible; theycorrespond to the equatorial section of PMI. It can alsobe inferred from the figure that the PMI combine to formlarger (inflated) PMI in such a way that the centres ofthe PMI are arranged in exactly the same fashions as are

G =-|co

(3)I l l l l l l l l l l l l l l l l l l

with the a ', directed from the centre to vortices of anicosahedron.

Comparing Eqs. (2) and (3) demonstrates thatquasicrystals will behave as crystals when investigatedvia diffraction methods, i.e.. as periodic structures butperiodic structures which would fill a six-dimensionalspace. This permits the use of regular crystallographyrules to approach the structure, except that Bragg peaksmust be given 6 Miller indices instead of 3. Formally, theknowledge of G and p(G) in Eq. (1) gives p | [ ) . i.e..the physical 3-dimensional structure of the quasicrystal.

During the year 1993. we have clarified severalcontroversial aspects of the structure of a particularquasicrystal that belongs to the AlPdMn system. Singleg ra in s of th is q u a s i c r y s t a l can be grown tocentimelre-si/.е dimensions via a C/rochralski procedure(Figure I). The quasiperiodic perfection which isachieved is revealed in high-resolution X-ray and y-raydiffraction measurements which show mosaic spreadsless than 0.001 ° full width at half maximum (less thanone third of the intrinsic Darwin width of Si( 111)).The anomalous transmission of X-rays due to dynamicaldiffraction fthe Bormann effect) has also been observed [ 11.

Basically, the structure of the AlPdMn quasicrystal isa hierarchical packing of atomic clusters calledpseudo-Mackay icosahedra (PMI). A PMI-cluster ismade of three successive "concentric" shells of atoms: aninner shell of 8 atoms distributed randomly on the sitesof a small dodecahedron, then an icosahedron of

M I N I M I

Fig. I: Optical micrograph of a single grain r>/ the AII'tlMnicmahedral uuaticrystul nhtaini'd via C;i>clinilski growth[scale in cm}.

(A) 40

ZA i = 4.562(A)

[Г, 1,0]//

(А)l-ig. 2: Example of planar section through the structure of theAlPdMn qiuuiicrystul. Equatorial cut* of PMI are underlinedami the T*-inflated PMI ax well.

C O U EG IE 6

о ЛII is

the centres of the atoms. The scale factor isт1 (т = 2cos36° the golden mean). An examination of tliewhole 3-dimensioiiiil structure shows that the iiiHutiongrowth mechanism develops iteratively.

Several experiments have been carried out at theNational Synchrotron Light Source Brookhaven. Inparticular the centric character of the icosahedralAlPdMn phase has been checked by measuring Bijvoetpairs above the Pd-K edge with a single grain [2].The anomalous X-ray diffraction close to the Pd edge hasalso been measured with the result that the partialstructure factor Fpj of the palladium substructure hasbeen determined (3|. Beyond a definitive confirmation ofthe existence of a very strong chemical order, these datahave brought a contradiction to the idea that atomicsurfaces in the 6-dimensional images should bepolyhedral objects sharply faceted. The results must beconsidered in the context of recent theoreticalsuggestions [4] that the atomic surfaces might haveI racially shaped borders.

Understanding of the dynam'" of quasicrystals hasalso made some progress in 1993. Further inela..ticneutron scattering data have been collected on triple-axismachines ai the LLB and (old) IN 10 data have beeninterpreted along with Mossbauer spectroscopymeasurements. The calculation of the dynamicalresponse of quasicrystals remains difficult since theprojection of atomic displacements on a plane wave basisdoes not reduce the number of independent parameters.Proposed models for the vibrational states ofquasicrystals are actually based on numericalcalculations on large cell periodic «pproximants [5].Inelastic neutron scattering measurements [61 havedemonstrated the existence of pseudo-dispersionbranches and pseudo-Brillouin zones in the acousticregime. Beyond that, the situation remains confused.No gaps are observed even when branches cross. But"phonon modes" broaden progressively foi iviomentumtransfers larger than 0.3-0.4 A"' (energy ЬхЮ"3 eV),while the "phonon branches" bend over and finallybecome dispersionless for momentum transfers above0.8: A'1 (energy 12xlO"3 eV). The broadening mightbe due to interactions of the acoustic modes with a "sea"of pseudo-optic localized modes. This idea is supportedby the fact that the broadening shows up at momentumtransfers corresponding to a length scale of about 10 A,which is precisely the size of the PMI atomic clusters.The purely elastic neutron scattering has also beenmeasured on a AlFeCu quasicrystal using the highresolution spectrometer IN 10 in the fixed energy windowmode (ДЕ = 10'6 eV). Typical temperature scansof scattered intensities at two momentum transfer valuesq are shown in Figure 3. A linear Debye-Waller likedecay is visible in the whole temperature range with

q < 0.41 Л"1 arid only below 7()0°K or so withq > 0.88 A"1. But this would correspond to a very largeDW factor, about 50 to 100 limes as large as thealuminium DW. This is interpreted by the existenceof phason modes, inducing correlated atomic jumps.In the larger q range and above 800°K, an enhanced dropof intensity is observed. This is confirmed, at higherenergy resolution (2.86xlO~8 eV) by Mossbauerspectroscopy data [7]. This additional drop can beattributed to high energy vibrational states, "localized"over a length scale between 7-15 A.

Altogether the atomic vibrations in quasicrystalsseem to generate fully extended "propagating phonons"of low energy (below 10"4 cV or so) and some sortof decoupled eigenmodcs of "cavities" correspondingto (about) 10 A rigid unit modes. This is consistent withthe structural analysis and would also explain the verylow thermal conductivity of quasicrystals |8J.

400 600 800 1000temperature (°K)

.^'<л

1 0 . 6

0.4400 600 800 1000

temperature (°K)

Fig. ': Typical temperature scans of purely elastic neutronscattering measured for an AlFeCu quasicryslal with a fixedwindow energy of 10"6 eV.

COLLEGE 6

References

[ 11 S.W. Kyciii, A.I. Goldman, T.A. Lograsso,D.W. Deianey, D. Black, M. Sutton, E. Dufrcsne,R. Briining and B. Rodricks, Phys. Rev.В 48 (1993) 3544.

[21 M. de Boissieu, P. Stephens, M. Boudardand C. Janot., J. Phys.: Condens. Matter6(1994)363.

[3] M. de Boissieu, P. Stephens, M. Boudardand C. Janot., Phys. Rev, Lett, (submitted).

[41 C. Godrèche, J.M, Luck, A. Jannerand T. Janssen, J. Phys. I France 3 ( 1993) 1921.

[5) J. Hafnerand M. Krajci, J. Phys.: Condens.Matter 5 (1993) 2489.

|6 | M. de Boissieu, M. Boudard, R. Bellisent,M. Quilichini, B. Hcnnion, R. Currat,A.F. Goldman and C. Janot, J, Phys.:Condens. Matter 5 ( 1993) 4945.

[7] C. Janot, A. Magerl, B. Prick and M. de Boissieu,

Phys. Rev. Lett. 71 (1993) 871.

[8] J.M. Dubois, S.S. Kang, P. Archambaultand B. Colleret, J. Mater. Res. 8 (1993) 38.

COLLEGE 8

Biological Structuresand Dynamics

F. Baud S.A. MasonP. Chenavas R.P. MayA.J. Dianuux E. Pebay-Peyroula (IBS)K. Ibel P.A. TimminsM.S. Lehmann L. VuillardP. Lindner G. Zaccai (IBS)

External members

At IBS

F. Bonnete B. JycrolV. Bracchi N. LouisJ. Chroboc/.ok D. MadcmC. Cohen-Addad N. NassarA.M. Di Guilmi M. RothC. Ebel F. Samaley

At EMBL

A. Barge M. HartleinF. Baudin T. KawashimaH. Belrhali U. KappC. Berthet J. LangowskiF. Borel K. LarsenS. Cusack R. LebermanM.T. Dauvergne S. PriceE. Di Capua R. RuigrokS. Doublié L. SeignoretC. Elster C. TaupinM.L. Ferri A. Thompson

At ESRF

C. BriindénA. KvickM. Saad

At Faculté de Pharmacie

M. Cussac

IntroductionAs in 1992. following ILL's reactor shutdown, many

activities and projects involving the use of neutrons hadeither to be stopped completely, or could only be pursuedpartially elsewhere. This has confirmed the fact that mostfacilities offered by the ILL cannot be replaced. The trendsof 1992 have been followed and scientific activity has beenmaintained through analysis of previous results and bymethodological work as well as by extending activities toX-ray diffraction or biochemistry. Collaboration with our

colleagues from the Institut de Biologie Structurale (IBS)and with those at the Grenoble outstution of the EuropeanMolecular Biology Laboratory (EMBL) has been carried onand still forms a vital element for the scientific life of ourcollege.

Progress in biochemical and molecular biologymethods—for example, the cloning and expression ofappropriately designed protein mutants and modified nucleicacids, or specific deuterium labelling of large functionalcomplexes—is revolutionizing structural studies includingthose by neutron scattering and diffraction. A special issueof Biophysical Chemistry devoted to Neutrons in Biology,edited by J. Zaccai, a member of the college, will presenta number of original papers on these aspects, describingwork at ILL and other neutron reactors around the world.It will be available at about the same lime as the start-upof the ILL reactor next summer.

Scientific Trends and Highlights in 1993Quasi-Lauc diffraction instrumentation

Detector development for the Quasi-Laue diffraetotneter,which was part of the proposed modernization programme,has continued and is described in some detail in thecontribution from the Large Structures Group to this AnnualReport. In addition further image-plate detector tests havebeen done.

The most important of these involved the use of a MAR-RESEARCH image-plate scanner converted to detectneutrons. The measurements were done at the VI instrumentof (lie Hahn-Meitner Institute by a mixed EMBL/ILL teamin collaboration with members of the Freie LIniversitat,Berlin. To detect neutrons a plate covered with gadoliniumoxide paint was placed in front of the X-ray detector duringexposure and removed during read out. A multi-wiredetector was also used for comparison [ 1 ].

The tests showed that recording of neutron reflectionsusing image plates on the VI spectrometer is possible, butthat protection of the plates against gamma-rays will berequired for routine data collection. Another approach forrecording of neutrons is by the use of gadclinium dopedplates. This was for technical reasons not tried, but earliermeasurements at Saclay have shown that this gives a muchbetter peak to background ratio. It is therefore most likelythat this approach will be the one followed for the prototypeversion of the neutron image plate detector presently underconstruction.

Structure of dodecyl sulphate - protein complexesat subsaturating concentrations of free detergent

The anionic detergent sodium dodecyl sulphate (SDS)effects solubilization of, for instance, membrane, ribosomaland viral proteins. SDS is widely used for size separations ofthese proteins as well as of water-soluble proteins or proteinsubunits, by gel electrophoresis and by molecular-sieve

COLLEGE 8

chromalography. Knowledge of the slruclure ofSDS-proiein complexes is useful for understanding and forfurther developing these important biochemical methods.SDS binds to water-soluble proteins approximately inproportion to the polypeptide length. On average, thesaturated complexes contain one SDS molecule per twoamino-aeid residues at moderate ionic strength.

Earlier investigations of SDS-protein complexes by anumber of physical techniques resulted in u number of partlyincompatible structural models. The first neutron small-angle scattering experiments had revealed the low resolutionstructure of the complex between SDS and the singlepolypeptide of a water-soluble enx.yme (452 amino acidp-biuuos). The saturated complex consists of three globularmicelles which are connected by short flexible polypeplidesegments.

Shortly before the reactor shut-down new experiments(in collaboration with Uppsala University, Sweden) wereperformed at subsaturating concentrations of free SDS inequilibrium with the complex. The data show a decrease instoichiometry from one bound dodecyl sulphate (DS) unionper two amino acid residues near the critical micelleconcentration (CMC) to one per four residues at halfthe CMC. At 0.3 CMC, a two-micelle complex is formed bythe recombination of the small amino-terminal micelle withthe middle one; and the centre-to-centre distance betweenthe carboxyl-terminal micelle and the middle one decreasesfrom 7.5 nm to 6.2 nm. These structural data allow us tobetter understand earlier results obtained withhigh-performance agarose gel chromatography of the sameSDS-protein complexes [2].

Functional motions in membrane proteins studiedby inelastic neutron scattering

The study of protein motions has gained considerableimportance in the search to understand biological function atthe molecular level. Because of their wavelengths andenergies, thermal and cold neutrons are particularly adaptedfor such studies. The Purple Membrane of Halobacterlumlialobiiini contains a single protein, bacteriorhodopsin, whichfunctions as a light-driven proton pump. Inelastic neutronscattering experiments on IN6 and IN 13 performed beforethe reactor went down have appeared in print this year.As described in last year's Annual Report, a detailed studyof the dynamics of this membrane in different conditionsof temperature and hydration showed strong correlationbetween the type of dynamics and the ability of the proteinto perform different aspects of its function. Thus when themembrane protein is vibrating harmonically, it can beactivated by absorbing a photon to release a proton on theoutside of the cell (where the proton chemical potential ishigher than in the cytoplasm). On the other hand, softanharmonic motions in the protein are required for it toreturn to its ground state by binding a proton on thecytoplasmic side. In 1993. the analysis of the neutron resultshas been taken further by using a recent structural model for

the protein and performing molecular dynamic calculations,and collaborations have been initiated for complementary(light absorption) speclroscopic studies. These have led toideas for new neutron experiments on deuterium labelledsamples that are now being planned for when the reactorstarts up again |3| .

Structure of Porins

Porins are a class of proteins found in the outermembrane of Gram-negative bacteria. They allow theselective passage through the membrane of polar moleculesup to a cut-off value in molecular weight that variessomewhat between different porins. The X-ray structures ofseveral different Porins have been solved in the last fewyears, each one revealing a secondary slruclure composedmainly of li-sheet. Crystals of membrane proteins areproduced aller solubili/ation of the protein in detergent thatis believed to mimic the membrane lipid in its interactionwith hydrophobia parts of the protein. The crystallisingparticle is in fact a mixed protein/detergent micelle. In theX-ray studies to date, however, no detergent structure hasbeen observed, due probably to disorder and low contrast.We reported last year on the organisation of detergent incrystals of Porin from the purple bacterium Klwdobactercapsulatiib |4|. We have now obtained results from crystalsof the protein from E. Coli \5\. The results from the twobacterial sources are rather different. In the Rhodobactercapxulatux case, the protein molecules and the detergentform two dimensional sheets in the crystals apparentlymimicking a bilayer membrane, although there is as yet nodirect evidence of a bilayer. There is no interaction betweenthe C8E4 detergent molecules in successive sheets, i.e. thereis no 3-dimensional continuity of the detergent phase, andthe crystal is formed solely through protein-protein contacts.In the case of the E. Coli protein the porin molecules forman extended three-dimensional network with only rathertenuous contacts between detergent micelles. In this case thedetergent, N,N dimethyl decyl amine oxide was deuteratedin the hydrophobic tail and despite the low resolution ( I3Â)it appears possible to identify the tail and headgroup regionsof the detergent molecules. This will allow us to analysemore closely the form of the interactions between detergentand proteins and to determine whether not only hydrophobicbut also polar interactions play a role in the stabilisationof the protein detergent complex.

Low resolution neutron diffraction on SOS ribosomalcrystals from halobacterium marismorlui

Ah iniiin phasing methods developed for phasing the lowresolution neutron diffraction data from 50S ribosomalcrystals (from halobacterium marismorlui ), based on directmethods, led to density maps for the 0% D2O and the 100%D->O data sets. Both maps were modelled by two densitylevels. In the 100% D2O map the high level should representthe proteins and the lower level the RNA; and vice versa inthe 0% D2O map. RNA and protein domains showed

С О L L Е С Е 8

reasonable siinihiriiies bol ween the two maps. It was ihendecided, in order to improve the phasing methods, loconcentrate the eflort on test data instead of experimentalones. Presently, starting from the test data we are trying toimprove the phasing method, principally by combiningdirect methods with supplementary information. These юмJala should also indicate the confidence level and thelimitations of our methodology |6|.

High resolution crystallographic studies on a new familyof small plant proteins rich in cysteins using X-raydiffraction

The hydrophobic protein from soybean (HPS) for whichthe structure was solved last year to 1.8 Л resolution showssimilarities (o non-specific phospholipid transport protein(l.TP) from plains. They both belong to u new family ofproteins characleri/.ed by a motif of К Cyslcins forming asimilar pattern of 4 disulfide bridges. Recent NMR resultsshow similarities in the three-dimensional structures despitea low sequence homology. In order to study the lipid bindingfunction of the LTPs, we cocrystallised the proteins withphospholipids. Two proteins are under study: a wheat LTPand a nuii/.e LTP. For both of them, two crystal forms wereobtained diffracting to 2.5 À on a standard rotating anode.Heavy atom derivatives are under study, weak derivativeshave been obtained already. A first density map to 6 Aresolution has been calculated. In order to interpret this mapwe have to improve the heavy atom derivatives [7|.

Storage-ring X-ray work

The enforced shut-down of the reactor coinciding withthe start-up of the ESRF synchrotron has given theopportunity for the ILL scientists both to learn more aboutsynchrotron radiation and to strengthen the contact with theirneighbours. It was therefore only natural for members of thecollege to participate in some of the first commissioningexperiments and measurements in protein crystallography.

The measurements - done in collaboration with and withhelp from the EMBL staff - were conducted on the Troikabeam line, which uses an insertion device (ID9) of thestorage ring, Indeed, they were the very first measurementsdone right after the final installation of the insertion device,an undulator, and they were therefore not only interestingfrom a protein crystallography viewpoint, but were also usedto learn more about these powerful sources.

For the measurements the Troika instrument wasequipped with an additional diffractometer, which was aMAR-RESEARCH image-plate detector on loan from theadjacent EMBL outstation, The monochromator was a singleSi (720) crystal in reflection, and the imageplate was locatedon the sample table of the Troika instrument. As this isplaced on air-cushions, it was very easy to changewavelength in the range from 0.7 À to more than 1.5 A, andboth standard protein crystallographic and multipleanomalous dispersion (MAD) studies for structure solutionwere carried out.

The normal protein crystallographic studies were carriedout as an introduction lo the MAD measurements. Theyiinolved projects from 1:MBL. ILL and the neighbouringIBS, and gave very satisfactory results. The MADmeasurement, which relies on the high energy resolution ofthe Troika set-up, was clone in collaboration with a groupfrom Columbia University. New York. In this case loin orfive sets of measurements were done around the absorptionedge of a heavy atom present in the protein structure, and bycombining this information the structure has now beensolved. During the measurement two modes were used,namely one where the magnet gap was kept constant and onewhere - for the first time - it was varied to obtain maximumintensity for the wavelength in question, and bothapproaches gave useful results |S].

Kxlrucellular matrix protein isofbrm separationfor cristallographie work

Т h с p г е .. e n с с of is о f о r m s . a ï s о c a l l e dmicroheterogeneity. is a consequence* of the posttranslational modifications of the polypcplide backbone.This is generally due to phosphorylalion. sulphation.or glycosylation. These modifications are frequent inextracellular proteins such as those from the extracellularmatrix.

0.6 mM

10 20 nm

/•'/.I1. I: Schematic .scale models of the nniliial dispositiono/ the I/tree proiein-ilecoraied micelles in Itn/fer coiildi/iint;l.f> niM ,S/)S (D.9 CMC, /fi/>) end oj llic tm>protein-decoratedmicelles in hnlJer containinK 4-(> niM SDS (0.3 CMC. hotlom).Tlic independent micelles N lN-termiiuil), M (middle) and С(C-leriniiiiil) oj tin1 three-micelle complex are connected, illsaturation, h\ flexible oligopeptide linkers about 5 or 6 amino acidresidues lout*; MY/// decreasing SDS concentration lo sidf-utio'aliiif>levels, the .\mall micelle /V coalesces with micelle M: and micelle Сapproaches' micelle M. Tlie difference in cimlra.sl he!» ее» thedodecs-l chain cores and tlic tiirronndiiiK protein-mlpnale shellis .shown h\ 11 different shading.

COLLEGE 8

It has been shown that (he microhclerogencity luis beenresponsible for some of ihe problems encountered with thecrystalli/.alion of proteins. C'rysials obtained from isoformmixtures are generally small and diffract poorly.

Isoeleclric focussing allows the separation of theisol'orms according to their isoeleetrie points. With massspectrometry, high resolution isoelectric focussing iscurrently the most sensitive method of protein analysis.Preparative scale isoelectric focussing under non denaturingconditions has been hampered by the lack of solubility ofnuiny proteins at (or near) their isoelectric point. Thisproblem has led to the discovery of new solubili/ing agentsthrough a collaboration between the ILL biochemistrylaboratory and а СНА -INSHRM laboratory in Grenoble.This séparai ion technique will now be applied lo improvecrystals that have been obtained with osteocalcin as well aswith a fragment of fibroneclin through a collaborationbetween the ILL and the IBS |9|.

Secretary: Laurent Vuillard

References

111 F. Cipriani, I-'. Dauvergne. A. Gabriel,C. Wilkinson and M.S. Lehmann:Submitted lo Biophysical Chemistry(special issue on Neutron Scattering to appear inJune 1994, edited by J. Zaccai, IBS, Grenoble)

[2| K.lbel. R.P. May., M. Sandberg, E. Mascher,E. Greijer and P. Lundahl: Biophysical chemistry,in press.

|3| M. l-'errand, A.J. Dianoux, W.Pelry and G.Zueeui.:Proc Natl.Acad.Sci USA, (1993) 90 9668-9672

|4| W. Welle. Th. Wacker (Freiburg)and P.A. Timmins (ILL): (work in progress).

|S| R.M. Garavito (Chicago), M. Zulauf (Basel),H. Pebuy-Peyroiila and P.A. Timmins (ILL):(work in progress).

|f>) M. Hisenstein.R. Sharin, Z. Burkowilch-Yellin,U.S. Gewil/. S.Weinstein, M. Roth,F]. Pebay-Peyrouhi and A.Yonalh:(1991 (Biochimie 73 847-886

|7] F. Bund, H. Pebay-Peyroula. C. Cohen-Addad,S. Odani and M.S. Lehmann:(1993).!.Mol.Biol. 231 877-887.

[8| M.S Lehmann, .1. Als-Nielsen. G. Griibel andJ.F. Legrand: Newslett. on Prot. Cryst. (1993) 28, 14.

|9| L. Vuillard, C. Braun-Breton and T. Rabilloud:Submitted.

C o L I EG E 9 a

Molecular Spectroscopy,Surfaces and Mesophases

I. AndersonH. BiittnerS. BramwellA.J. DianouxC. DollB. FaragoA. HeidemannG. Kearley

Kxternal members

J.P. Beaufils (ENS Lyon)M. Bée (UJF)M. Bcnmounu (UJF)E. Geissler(UJF)A. M. Hecht (UJF)

Introduction

H.J. LauterA. LiedK. LissA. MagerlJ. PannetierC. RitterP. Terech (CENG)

I. Morfin(UJF)C. Poinsignon (UJF)D. Quenard(CSTB)F. Rieutord (CENG)M. Rinaudo (UJF)

Despite Ihe reactor shutdown and the departure of manycollege members, there has been considerable scientificactivity. Much of this has resulted from visits to otherlaboratories, particularly LLB Saclay, and it is hoped thatthe links formed between ILL scientists and those of otherinstitutes will be mutually beneficial for years to come.

Low-energy excitations,density of states experimentsAmorphous - crystalline ethylbenzene (ILL, NIST)

The dynamics of ethylbenzene was investigated using thethree-axis instruments BT4 and BT9 at NIST (Frick,Trevino, Erwin). Previous experiments using an elastic scanon IN 13 revealed that the mean squared displacement <u >has anomalous behaviour with increasing temperature.A strong increase of <u2> with respect to lower temperaturesis observed between 120 К and 140 К before it drops to amuch lower value. Following a further, weaker increase itagain decreases.

New experiments on deuterated ethylbenzene at NISTshowed that these dynamic anomalies are connected torecrystallization phenomena (Fig. 1). Two differentcrystalline phases were found above 140 K. Comparing thelow-frequency scattering of amorphous and crystallineethylbenzene (Fig. 2) it can be seen that the intensity at lowfrequencies for the amorphous sample is strongly enhancedwith respect to the crystalline sample. Fig. 2 shows a stronglow-frequency hump below 8 meV in the range where thecrystalline sample has a much lower and almost frequency-independent intensity. Thus before recrystallizing the low-

frcquency modes increase drastically in amplitude and showanharmonie behaviour. These are the dynamic precursors ofthe structural rearrangement from a disordered solid towardsthe crystal.

Dynamics of pristine and doped polyact'lylone(ILL, LLB)

Polyacetylene, (CH)X, is the simplest example ofa conjugated polymer. Interest in the physical propertiesof this molecule has increased since it has been found that itcan be chemically doped to •metallic' levels of conductivity,values as high as 145 000 Scm"' having been reported. In thedoping process, carriers are generated by charge transfer,but the spectacular increase in conductivity is due to changesin the electronic structure of the polymer backbone.The mechanisms that lead to metal-like values forthe conductivity huvc been studied theoretically, mainlyin lightly-doped systems. In heavily-doped regimes (examinedhere) a complete delocali/ation of carriers is assumed.

Until recently vibrational data for polyacctylene werelimited to a few Raman and infrared intrachain modes andthus theoretical efforts have concentrated on the dynamicsof the isolated chains. However, the modes which dominatethe vibrational atomic mean-squared displacements are thoseat lower frequencies (< 20 meV). Recent inelastic neutronscattering experiments from stretch-oriented c/.v-rich andrran.s-rich polyacetylene have enabled the vibrational densityof states, G(o) of the system to be determined in thedirections parallel and perpendicular to the average chainaxes, with good resolution in the low-frequency region.The experimental G(co)s were found to be highly anisotropicand exhibit considerable differences between the cis-and tnms-conformers.

A detailed interpretation of the observed vibrationalspectra based on the neutron data alone is not possible.However, information can be obtained by performing

1.8 104

1.6 104

1.4 104

Ц1.2 104

l l . O l O 4

deuteratedethylbenzene

T= 75 К— T = 140 К :

T= 170 К .

0 0.5 1 1.5 2 2.5 3 3.5 4

F/Я. /: Static structure factor of deuteratedethylheiKene fora quenched sample (thick line) and patterns at two temperatures(I40K and I70K) of the annealed sample.

COLLEGE 9 a

molecular-dynamics simulations and calculating neutronscattering properties from the resulting atomic trajectories.R e c e n t l y , s i m u l a t i o n s of c r y s t a l s of с /л- andmiH.ï-polyaceiylene molecules of different chain lengthshave been reported 111. Because the dynamics of interest isvihrational, harmonic analysis can (in principle) be appliedto these systems. However, molecular-dynamics simulation,in which the harmonic approximation is not required, isexpected to give a better representation of the effectivepotentials for the large-amplitude, low-frequency vibrations.In this work the density of slates was calculated from themolecular-dynamics trajectories by numerical Fouriertransformation of the velocity autocorrelation functions.

The low-frequency dynamics (0-20 meV) ofsodium-doped f/wi.v-polyacctylene has recently beeninvestigated using a combination of incoherent neutronscattering spectroscopy and molecular-dynamicssimulations. These simulations were perfoimcd using amolecular-mechanics potential-function with a modelsystem explicitly including the three-dimensional crystalenvironment | 2 | . Time-dependent mean-squareddisplacements and vibrutional densities of states are

*l\J\J

§200и

ethylbenzeneprotonated À 4 КBT9

amorph 50 К

100 К

д 4 К

crystal en is° OVy l\

^ l I . 100 К

' ' v \

'. Vh/u . . */(f^^^\^^°'"'° Ь-/°о 0°

#;w»?W$fc2 4 6 8 10

Е (meV)

оно.б

5 10 15

frequency (meV)

Fig. 2: Low frequency scattering of quenched ethylbenzene (lines)in comparison with crystalline ethylhen;.ene (symbols) as measuredon the thermal triple axis spectrometer BT9, NIST.

5 10 15 20frequency (meV)

Fig. 3: Simulation-derived density of stales in the directionperpendicular to the chain axesa) trans-polyacetyleneb) Na-doped (12.5 at. c/c) trans-polyacetylene.

calculated from the simulations of the pure and dopedsystems. The simulations are decomposed to determine thecontribution of rigid-body motions to the atomic trajectories.From these simulations there is an indication that themean-squared displacements of the polyacetylene atomsbecome close to isotropic on doping. Experiments(performed with the instrument MIBEMOL at LLB) andsimulations are in accord that doping results in a markedchange in the vibrational density of slates in the directionperpendicular to (he chain axes, a broad minimum appearingat ~ 16 meV. This spectral region is dominated byintramolecular torsional displacements, see Figs. За and 3b.

Quasielastic scatteringDynamics of urea inclusion compounds(ILL, University of Bordeaux)

Long chain hydrocarbon molecules such as n-alkanes areknown to form inclusion adducts with urea. In urea inclusion

COLLEGE 9 a

compounds, llic hydrogen-bonded network of ureamolecules (hereafter called the host) contains essentially"infinite" and parallel channels of approximate diameter5.2 A (at room temperature) in which the n-alkane chains(the guests) are trapped in an almost "all trans"conformation. The n-alkane/urea inclusion compounds are

known to undergo a structural phase-transition from a low-temperature phase (LT) to a high-temperature phase (HT) ata temperature that depends on the length of the guestmolecules. In general, (he transition temperature increaseswith the length of the guest molecule. In the LT phase (he-host substructure is orthorhonibic whilst it is hexagonal in

1 "ОCO

C,0H33/Urea-d,

C n H 2 4 /Ureod 4

2 - 1 . 5 -1 -0.5 0 0.5 1 1.5 2energy transfer/meV

- 2 - 1 . 5 -1 -0.5 0 0.5 1 1.5 2energy transfer/meV

- 2 - 1 . 5 -1 -0.5 0 0.5 1 1.5 2

energy transfer/meV

- 2 - 1 . 5 - 1 - 0 . 5 0 0.5 1 1.5 2

energy transfer/meV

C,5H32/Urea-d4

Fig. 4: Qua.iiclaslic neutron scattering spectra о/С„//211+2/игевinclusion compounds for n — 10 to 15 at 50 K.The scale expansion factor is 50.

2 - 1.5 - 1 - 0.5 0 0.5 1

energy transfer/mfV

COLLEGE 9 a

the HT phase. The guest substructure is essentiallycharacteri/ed by its one dimensional packing with a periodicrepeat distance са. An important property of urea inclusioncompounds is that the ratio of c,, versus the host latlice-parameter C|, is not a rational number: urea inclusioncompounds are therefore incommensurate compositestructures in both their LT and HT phases, it should be notedthat the hexagonal structure of urea is not stable without theguest component: the stable crystalline structure of pure ureais tetragonal and does not contain empty channels.

Pioneering 'Н-NMR works revealed that in the HTphases of the compounds, the n-alkane guest undergoes lastreorientations about the С axis of the urea channel.Although the existence of translational fluctuations wasdetected by X-ray diffraction, it is only very recently that thetranslational motions of the guest molecules along thechannel axis could be analy/ed precisely by means ofincoherent quasielastic neutron scattering (IQNS) technique.These experiments, performed on the n-nonadecaneC|i)H4o/urea inclusion compound, have shown that withinthe characteristic lime scale of the spectrometer, largeamplitude diffusive réorientations of the guests wereobserved but could not be assigned to 271/6 jumps, as usuallyassumed regarding the hexagonal symmetry of the ureachannels. In the LT phase of the samples, the reoricntationulmotions were fro/.en-in and side-peaks assigned to low-frequency longitudinal oscillations of the hydrocarbonchains were observed at about 1.2 meV. Such low-frequencyinelastic peaks we. p not observed in the crystalline phase ofpure n-nonadecane samples and other related inclusioncompounds. It must also be pointed out that these inelasticpeaks cannot be assigned to any kind of intramolecularvibration of the n-alkane chains involving the longitudinaldisplacements of the hydrogen atoms, such vibrationalmodes (the longitudinal accordion "LAM" modes) beingexpected to be observed at about 12.5 meV forn-nonadecane. It is therefore expected that these low-energyexcitations are characteristic of the one dimensional packingof the guest molecules within the urea channels so thatthe mean frequency of the oscillations should be a functionof both the chain length of the n-alkane chain and also ofthe specific interactions between the urea host and the guest.

Incoherent quasielastic neutron scattering experimentswere performed by using the spectrometer M1BEMOL of theLLB-Saclay on a series of urea inclusion compoundsn-CnH-)n+-)/urca-d4 with n = 5<-»9. Using semi orientedsamples, the spectra were recorded in two geometries, i.e.with the Q momentum transfer vector parallel (Q,/) andperpendicular (Ql) to the urea host tunnel axis. It wastherefore possible to investigate separately reorientationaland translationul motions in both the low temperature (LT)and high temperature (HT) phases of the samples. The low-frequency excitations observed in the LT phase and only inthe Q,/ geometry can be assigned to the "sliding mode" ofone sublattice (the n-alkane guests) with respect to the other

(the urea host). Fig. 4 shows that the mean frequency of this"sliding mode" does not follow a simple law with the chainlength of the included alkane. It seems to depend upon theparameter c,,/C|, which characteri/es these incommensuratecomposite structures | 3 | . The spectra have beenquantitatively analy/.ed by meuii" of a model of dampedoscillator |4| and the results interpreted on the basis of thestructural properties of these composite incommensuratesystems. On the characteristic time scale of the experiments,réorientations of the n-alkane chains are effective only in theHT phases of the compounds. Fig. 5 shows the evolutionwith temperature of C^Hi^/urea inclusion compound andthe fit with the model.

Diffusion of'Ni"+ in l^Mo^Sjf(ILL, University of Kiel, TU Berlin)

Binary and ternary molybdenum cluster chalcogenides(Chevrel phases) of composition Mo()Xs and A4Mo(,XN

show a manifold of chemical and physical propertiesdepending on the nature of the chalcogen atom X. the natureof the ternary metal A, and the sloichiometry of the latter.They are able to undergo reversible lopotactic redoxreactions at ambient temperature via electron/ion transfer.Electrons are accepted by appropriate levels of the host-lattice conduction-band and the resulting negative excesscharge is compensated by the simultaneous uptake of mobilecations A+ or A2+ which occupy empty sites in the latticechannels.

Small cations, such as Li+, Cu+ or Ni"+. form the socalled Chevrel phases of type II where the rhombohedrulunit-cell is compressed in direction of the threefoldsymmetry-axis. This leads to a squeexing of the Xx cubesand in consequence to the formation of two times sixpotential lattice sites with distorted tetrahedral symmetry.These sites arc arranged on two concentric rings around theunit-cell origin. The large number of possible lattice siteswithin the empty channels should facilitate the diffusionof the guest ions within the host lattice.

Fig. 6 shows a projection of the 3d-framework of innerand outer sites of М!2Мог,58 around the unit-cell origin (Д).Possible jump distances are indicated and vary betweenI.2Â and 2.9Â. Electrochemical work gave evidenceof fast long-range diffusion for e.g. L^Mo^S^with D,3(H,K) = 1.4 x I0~';civr/s or Ni2MoflS8 withDOOOKI = '-7 x l()"4 cirr/s. Quasiclastic and inelasticneutron scattering experiments were performed on INK)to study the motional behaviour of the intercalant Ni~+

in NiTMof,Sx on a microscopic scale. T-dependent fixed-window scans revealed a motional broadening of the spectraabove 250K. The inelastic spectra measured as a functionof scattering vector and temperature contained a constant20r/r of elastically scattered intensity |5]. This correspondsto the incoherent scattering cross-section of the immobilehost lattice MofiSx and indicates the Ni~+ motion to bea long-range diffusion process.

COLLEGE 9 a

C13H2e/Ure*d<|x2)

T= 161 К

•2-1.5 -1 -0.5 0 0.5 1 1.5 2

energy »ransfer/meV

(b) C13H2e/Urea-d4(xlO)

Т = 109 К

2-1.5 -1 -0.5 0 0.5 1 1.5 2

energy transfor/meV

C,3H28/Urea-d,(x50)

Т = 50 К

-2-1.5 -1 -0.5 0 0.5 1

energy transfer/meV

F/.ç. 5: Quasielastic neutron scattering spectra of C/ i

inclusion compound for 3 temperatures:a) T = 50 К - expansion 50;b)T= 109 К (below the transition temperature) - expansion 10:c) J - 161 К (above me transition temperature) - expansion 2.

A simple jump-diH'usion model Cits the T- and Q-dependenee of the inelastic spectra; tc,,= 1.5 x 10"'2s,EA=24kJ/mol. The jump vector amounts to 2.1 A and can becorrelated to the distances indicated in figure 6, assumingthat thermal averaging merges the six inner sites into theunit-cell origin. A long-range diffusion process consistsof intracluster jumps of 2.3À and intercluster jumps of 2.1 A(Fig. 6). Most surprising is the high value of the diffusioncoefficient which amounts to О ( 1 ( Ю К ) = 3 x l()"ycirr/s.To our knowledge this is by far the highest value found byneutron scattering techniques for the diffusion of a transitionmetal within a solid compound at room temperature.

Quantum RotationsRotation/Precession of МНЦ groups in HofmannClathrates (ILL, CNRS, ANSTO, LLU, ISIS)

Although quantum rotation of molecular species is oftenregarded as an excellent example of a single-particle motionseveral recent studies have revealed pronounced couplingeffects. The temperature dependence of the j=()<->j=ltransitions of the NH? rotor in Ni(NH^2Ni(CN)4.2CfiDft

suggest these transitions become strongly coupled todiffusive motions of the NN3 unit as the temperature isincreased |6j At temperatures below about 4K the j=()oj=ltransitions give rise to sharp inelastic features but as thetemperature is increased these peaks develop a Lorent/.ianshaped foot which steals intensity from the parent peak(Fig. 7). At around 30K the inelastic peaks are almostunshifted but appear completely Lorent/ian with appreciableintensity spreading beyond ImeV. The rotational constantfor NH} is about 0.67. Any inhomogeneous broadeningof the j=0<-»j=l peaks does not extend beyond this value.These observations are difficult to understand within (he

Fit;. 6: Cluster of inner (<>> and outer (O) Ni sites aroundthe unit cell origin (Л) in Ni^Mof)Su

C o n EG E 9 а

-1.2 -0.8 -0.4

/•>',!;. 7: Ineltixtif neutron spectra of the Ni_Ni Hofmann clathrateих » function o,''temperature recorded on the MIHEMOLspectrometer at Ll.lt Sttchty.

normal concept of free-rotation since the NH^ rotor can onlybecome hindered by interaction with the motions of itsenvironment.

The low-temperature crystal structure has beenredetermined [7| and the NH;, groups occupy sites of time-averaged 4-fold symmetry due to dynamic rotationaldisorder. However, the INS vibrational spectrum at 20Kreveals that the instantaneous NH^ symmetry is no higher

- 1.2-1.2 1.2

Fig. 8: Trajectories of the three H-atoms {square, triangle andfilled circle) during а 2л/3 rotation following the minimum energypath. The open circles show the corresponding trajectoryof the centre of the H ; triangle.

than Cs |8 | . Again, this suggests considerable interactionwith the environment.

A possible explanation for these inconsistencies is basedon the rotation of a triangle within a square.

The sum the of the distances, r, between the threeH-atoms and the four nearest neighbour atoms is constantregardless of the orientation of the NH^ group. The totalrepulsive potential between the triangle of H-atoms and its4 nearest neighbours (which form a square) can be reducedby allowing the centre of the triangle to move away from thecentre of the square. During а 2rc/3 rotation of the H3triangle, the position of the centre of the trianglecorresponding to the minimum Z(l/r ) describes a circle ofradius 0.26Â around the centre of the square. Fig. 8 showsthe trajectories of the three H-utoms, and the centre of the H^triangle, during the 2л/3 rotation which followsthe minimum-energy route.

All three H-atoms follow each other around the sametrajectory - which now has four-fold rotational symmetry.The minima of this new rotational potential correspondto orientations where two H-atoms experience equalpotentials whilst the third H-atom experiences a higherpotential leading to an effective symmetry of Cs.

References

11 ] A.J. Dianoux, G.R. Kneller, J.L. Sauvajoland J.C. Smith, J. Chem. Phys. 99, 5586 ( 1993).

\2\ A.J. Dianoux, J.L. Sauvajol, G.R. Knellerand J.C. Smith, J. Non-Cryst. Solids, in press.

[3] A. El Baghadi, F. Guillaume, H. Boysen,A.J. Dianoux and G. Coddens, Proceedingsof the Conference "Quasi-Elastic NeutronScattering", San Sebastian, Spain,Sept. 27-28, 1993, to be publishedby World Scientific Publishing Co.

|4] F. Guillaume, С. Sourisseau and A.J. Dianoux,J. Chem. Phys. 88, 1721 (1991).

|5] C. Ritter, C. Nôldeke, W. Press, U. Stegeand R. Schôllhorn, Z. Phys. B, 92, 437 (1993).

[6] F. Filiaux, H.G. Biittner, G.J. Kearley,to be published.

|7] H.G. Buttner, G.J. Kearley, C. J. Howardand F. Filiaux, Acta Cryst.B., in press.

|8] G. J. Kearley, G. Coddens, F. Filiaux,J. Tomkinson and W. Werner, Chem. Phys.,176,279(1993).

Secretary: Gordon Kearley

C o L L EСE 9 a

action

basedMagnetic excitations in rare earth dimers.High-resolution inelastic neutron scattering

Hans U. Giide!

Institut t'iir anorganisehe und physikalische Chemie,

Frcieslras.se 3, CH-3000 Bern 9, Switzerland

Understanding the nature of magnetic interactionsbetween neighbouring transition and rare-earth rneta)ions in insulating lattices is a prerequisite forunderstanding macroscopic magnetic phenomena and forthe design of new magnetic materials. The area of"Molecular Magnetism" is presently very active [1].The bridging aeometry, connectivity, dimensionality,and the combination of magnetic building-blocks aresystematically varied to produce compounds with novelmagnetic properties. Dimcrs and higher clustersof magnetic ions can be considered as molecular modelsfor a detailed study of the microscopic magneticinteractions. Co-operative phenomena arising fromextended interactions do not complicate the situation inthese systems, and an analysis in terms of simplemolecular-models is possible.

We have combined high-resolution inelastic neutronscattering (INS) and optical spectroscopy to investigatetransition-metal and rare-earth metal ion clusters in detail|2-6], Here we illustrate the results obtained forrare-earth dimcr systems over the past few years bypresenting two selected examples. The family ofcompounds Cs3R2X4 (X = СГ Br"; R = Sm3+...Lu3+, Y3+)is ideal for such a study [7]. The RoXcj dirncrs consistof two face-sharing octahedra, as shown in Figure I .The compounds crystallize in space group R3c, with thetrigonal dimer-axis parallel to the crystal с axis. Thecompounds can be synthcsi/e<! by the methods describedin réf. (7|. We used the rare-earth oxides as startingmaterials and transformed them to halides cither withHX or with NH4X. Mixed crystals can be prepared, andby using C s ^ X y as a host, the single-ion properties ofthe R'1+ ions can be studied for comparison. On the otherh « nil, irivalent tiansition-metal ions T3 + can beincorporated into the structure, thus producing mixed

Figure 2 shows INS spectra at 5.8K of polycryslallineCs^YbiCly and Cs^Yb^Biy measured on IN6 |6]. Oneprominent inelastic peak is observed for both compoundsin energy loss and energy gain. The peak energies are3.25(3) em"1 and 3.00(3) cm"1 in the chloride andbromide, respectively. Since Yb3+ in an octahedralcoordination has a well separated Kramers doubletground state, the most simple theoretical model can beused for the intradimcr exchange interaction: coupling oftwo Kramers doublets. Both a Heisenberg and an Ising

-Dt_О

5.8 К

Cs3Yb2CI9

Cs3Yb2Br9

- 4 - 3 - 2 - 1 0 1 2 3

Fig. I: Schematic illustration of the structure

of the /?2^9 Miners.

Fig. 2:1 Mastic neutron scattering spectra ofpolycryxtallineCsjYhi*. ' .tind ^х^Ь2Иг,/at 5.8 K. Conditions: instrumentIN6. sum of all scattering angles, wavelength 5.9 A.(From réf. 6).

COLLEGE 9 a

г 4 Г2 + Г6

S=l /E = S 3 ï

'• г,-0 S-П • '

Heisenberg

Г, + Г,"\ M=0

.•' M=±l

Fig. 3: Energy splitting of two exchange-coupled Kramersdoublets according to et/s. (I) and (2). Tin- dimer levels aredesignated in the /->)/, dimer point group.

model split the ground slate into two dimcr levels,whereas an XY model produces three dimer levels withequidistant energies. The Heisenberg and Isinginteractions for a dimer can be written as:

with the Junctions (3) and (4) in Figure 4. The intensityof the inelastic peak disappears as Q approaches /его,the behaviour expected for a S = 0 —» S = I dimerexcitation in the Heisenberg model (eq. 3). The sizeof the singlet-triplet exchange splitting is remarkablefor a rare-earth system. Using the Humiltonian ( I ) we get:

2J = -3.25cnï' for Cs3Yb2Clg

2J = -3.00 cm-' for Cs3Yb2Br9 (5)

We attribute these high values of the exchangeparameters to the close proximity of the Yb-1+ ions in thedimer, resulting in a relatively strong overlap of therelevant magnetic orbitals. The difference ofapproximately 10% between Cs3Yb2Cli; am.i Cs3Yb2Bryis reminiscent of exchange coupled transition-metal ionsystems willi face-sharing octahedra.

In the next example. Cs3Dy-iBri,, we investigate (heexchange splitting of the lowest-energy crystal-field (CF)excitation |°]. Its energy is determined in the dilutedCs3Y2Br9:IO%Dy sample, and Figure 5a shows thecorresponding region in the 1.5K INS spectrum

Heisenberg: Hex = - 2 J S ! • S2 (1)

Ising: Hex = - 2 J Z S ! • S 2 (2)

The corresponding splitting pattern for anti-ferromagnetic coupling is shown in Figure 3 with thedesignation of dimer levels in D3h notation. The arrowsindicate the allowed INS transitions.

In order to distinguish between the Heisenberg andthe Ising case we have to consider intensities,in particular their dependence on the scattering vector Q.It can be shown that the Q-dependence of the signal fromthe dimer excitation in the Heisenberg and Ising modelsis given by [6]:

Heisenberg: 1(0) ~F2(Q)i1 - 3 ' " ^ П (3>! QF>

Ising: |(Q) ~F2(Q) (4)

F(Q) is the magnetic form-factor and the squarebracket in eq. (3) represents a so-called interference term|8]. This factor is very typical of dimer excitations, and itreflects the separation R of the two magnetic ions in thedimer. Since this factor tends to zero as Q approacheszero, it is very important to measure intensities down tothe lowest Q values. We used IN5 for thesemeasurements. The experimental results are compared

eq. (4)

Fig. 4: Observed (circles with estimated error bars) amicalculated (thin lines) INS intensity of the singlet-tripletexcitation as a function ofQ. The thick lines are fits ofeq.(J)with a scaling factor as an adjustable parameter. The function4 is included in (ai for comparison. (Adapted from réf. 6).

COLLEGE 9 a

measured on IN5, with a single peak at 15 cm .Figure 5b shows the same CF excitation in the undilutedCs^Dy-JàTg. The effect is dramatic. Instead of a singleline we observe a highly structured spectrum coveringthe energy-range from 10 cm"1 to 17 cm"1. At least fourcomponents are resolved, and for a full analysis we needtheir temperature-dependence and their Q-dependence.Both the ground and the first excited CF states are splitby exchange interactions. In addition to the transitionsshown in Figure 5, we observed a transition between twoexchange-split levels of the ground state at 0.65 cm"',exhibiting the same Q-dependence as the Yb2Brcexcitation presented in Figure 4. Using all the observedINS data, supplemented by high-resolution opticalspectra, we obtained the empirical energy-level schemeshown in Figure 6a. For an analysis of the relative INSintensities and their Q-dependence, the appropriatecross-section formulae were derived.[3]. The computedenergy-level scheme shown in Figure 6b was obtainedby diagonalizing the Hamiltonian:

л •- 1 л 2 ~Hoimer = HCF + HCF + Hex (6)

^ 1 л 2

where HCF and HCF describe the crystal-fieldsplitting of the two Dy3+ ions and Hex is a Heisenberg

B < c r B ' iVA - > A '

B,C -> C'

hi• 1.5 К

-20 -16 -12

E [cm'1]

Fig: 5: Inelastic neutron scattering spectra ofpolycrystatlineCs3Y2Br9 10% Dy34" (a) and Cs3Dy2Br9: (b)) Instrument IN5,wavelength 4.8 A.

exchange operator with 2J = -0.05 cm"'. The calculatedenergies and relative intensities are in good agreementwith the data. It is not obvious that this splittingcorresponds to the Heisenberg model. In the ground statewe do not have a simple singlet-triplet splitting as inYb2Br9

3" because of the proximity of the other CF states.In the excited state we have a total of eight dimer-levels.The reason for this doubling with respect to the groundstate that either of the two Dy3+ ions of the dimer can bein the excited CF state. The proper dimer wave-functionsare thus given by:

1 I GS ES ES GS^т i = —~— 1Ф1 Ф 2 — Ф"! Ф 2 I (T\

1/7)" (.'/

The magnetic ordering in Dy compounds withextended interactions can often be interpreted in terms ofan Ising model [10]. This is usually attributed to a highlyanisotropic g-tensor of Dy . In our Dy2Br9 dimer theobserved behaviour cannot be reproduced by an Isingmodel. In the analogous Ho2Br9

3" dimer, on the other

C1 15.6

B' 14.4

A1 12.3

Fig. 6: Exchange splittings of the first two crystal-field levelsin Cs}Dy2Brg.

a) Experimentally determined splitting using INS.The arrows correspond to the observed transitions,

b) Calculated splitting using eq.(5) with a Heisenbergexchange Hamillonian and 2J = -0.05 cm"1.

COLLEGE 9 a

çj hand, the Heisenberg model was found to be inadequatet and a tensor formalism was used to account for the

observed INS data [11].О

e The direct observation of exchange-splittings in then lowest CF states by high-resolution INS and optical

spectroscopy of 0531*2X9 dimer compounds has led to abetter understanding of the nature of the magnetic

d coupling between neighbouring rare-earth metal ions in

e insulating lattices. Accurate values for the exchange

s parameters can be directly derived from the data.

References

[I] O. Kahn "Molecular Magnetism",Verlag Chemie, 1993.

[2] H.U. Gudel, in "Magnetic Molecular Materials"(D. Gatteschi et al., editors),Kluwer Academic Publishers, 1991, p. 333.

[3] A. Furrer, H.U. Gudel and J. Daniel,J.Less-Common Met 111, 223 (1985).

[4] H.U. Gudel, A. Furrer and J.Kjems,J. Magn. Magn. Mater. 54-57,1453 (1986).

[5] A. Furrer, H.U. Gudel, H. Blank andA. Heidemann, Phys. Rev. Lett. 62,210 (1989).

[6] H.U. Gudel, A. Furrer and H. Blank,Inorg.Chem. 29,4081 (1990).

[7] G. Meyer, in "Inorganic Synthesis"(S.L. Holt, éd.), Wiley, 1983 Vol.22, p.l.

[8] A. Furrer and H.U. Gudel, Phys. Rev. Lett. 39,657 (1977).

[9] M. Aebersold, H.U. Gudel, A. Furrerand H. Biittner, Inorg. Chem. 1994, in press.

[10] L.J. de Jongh and A.R. Miedema,Adv.in Physics 23,1 (1974).

[II] A. Furrer, H.U. Gudel, E.R. Krausz and H. Blank,Phys. Rev. Lett. 64,68 (1990).

COLLEGE 9b

Large molecules

P. ChieuxB. FaragoB. FrickK. fbel

External members

J.P. Beaufils (ENS Lyon)M. Bee(UJF)J.F. Legrand (UJF)

C. Lartigue (CNRS)P. LindnerR. Oeser

C. Poinsignon(UJF)D. Quenard (CSTB)P. Terech (CENG)

Scientific activities of some college members havecontinued outside the ILL in 1993. Bernhard Frick was onleave at NIST for 1 year where he did tests at thebackscattering spectrometer and measurements with glassesusing triple axis and TOF instruments: he returned to ILL inJuly 1993. During the last two years Bela Fatago spent halfof his time at LLB where he was putting into operation theneutron spin echo experiment; he is back since January1994. Pierre Terech returned from a stay at NIST where hewas working in the polymer division from August 1992 toFebruary 19Q3; he left ILL in spring 1993 and took up aposition at CENG. Peter Lindner did various SANSexperiments at LLB Saclay and at Ris0 National Laboratory.Colette Lartigue who worked for two years at the UniversityJoseph Fourier, Grenoble, came back to the ILLin January 1994.

Scientific HighlightsCold neutron diffraction by volume phase hologramsfor the study of light-induced reactions in photopolymers

Photosensitized PMMA slices of 2 mm thickness wereprepared from a fluid deuterated MMA (C5OiD8) monomer,a thermal initiator and a photo-initiator. If the mixture iskept for 15-20 h at 50°, an uncompleted thermalpolymerization takes place which supplies the three essentialconstituents of the polymeric material for the storage ofvolume phase holograms: about 90% of the polymerPMMA: 10% of the monomer MMA; and the photo-initiator.

So far, little direct evidence is available about themechanism which results, upon illumination, in themodulation of the light-optical and the neutron-opticalrefractive indices. Our speculations are the following: thePMMA molecules can be considered as chains of monomerunits linked by chemical bonds and forming a nearly staticmatrix. Within this matrix the free monomer molecules canmove around. One chain unit has the same coherentscattering length as a free monomer molecule itself, becauseit consists of the same nuclei. The relevant difference betweenfree monomer molecules and monomer units in the polymerchain is the fact that the first are mobile and the latter not.

If some region of the block is illuminated, the photo-initiatoris activated and starts the growth of polymer chains from theresidual monomer molecules. This means that mobilescattering units, which come along by the random walk ofthe diffusion process, are trapped in illuminated regions.To support this process the samples are heated totemperatures of 50°C for several hours after illumination.The photo-induced polymerization obviously provokesa change in the number density of the scattering units [ 1 ].

All experiments have been executed using permanentholograms which have been prepared by using theholographic set-ups in Osnabriick. The installation of such aset-up at the sample position of Dl I would allow us tofollow up the structural changes during the writing process;and the decay of the density modulation in anyphotosensitive material as a function oi a number ofinteresting physical parameters, as temperature, light- andUV-illumination, etc. A conceptual design of such aninstallation is in preparation.

Fig. I shows the diffraction probability for the 1st peakof diffraction versus angle of incidence of the neutron beam.The neutron wavelength was 1 nm, and the grating periodwas 249.2 nm. No changes in reflectivity could be detectedafter 6 weeks; after 4 months, however, the reflectivity wasdiminished by more than two orders of magnitude.

Our artificial thick gratings exhibit cold neutrondiffraction properties which are comparable to those ofmonochromator crystals for thermal neutrons. One of thepossible neutron-optical applications became alreadyimportant in the context of the calibration of the new neutronsmall-angle camera at the HM1 in spring 1993.

_p1.2<N

Ь 0.9

• initial

о after 6 weeks* after 4 month

90 3,to

60 "I-

30-0.20 -0.10 0.00 0.10 0.20

angle of incidence [degree]

Fig. I: Diffraction from а 1.8 mm thick sampleiifD-PMMA: DMDPE containing ti Laser-generated hologram.ID and ln are diffracted ami incoming intensity, respectively.

COLLEGE 9 b

Similar gratings were prepared in undeuteratecl PMMA.It has been shown in December 1993 that gratings of upto 1600 nm lattice constant can be used to calibrate theBonse-Hart camera at ESRF |2|.

2D-Melting of a Langmuir Monolayer investigatedby Neutron Reflectivity

The melting and crystallization of monolayers of fattyalcohols at the air-water interface has recently beeninvestigated using grazing incidence diffraction ofsynchrotron radiation. For the series of l-alkanols rangingfrom СцНщОН (Tm2D=2°C) to C I 6H3,OH (Tm2D=67°C).these experiments have provided detailed information on the2D crystalline structures but nothing on the properties of theliquid phase which ought to be determined for a bettercomprehension of the thermodynamics of the 2D meltingprocess.

dodecanol

solid phase (30°)

liquid phase (42 •a—••

0 0.1 0.2 0.3 0.4 0.5

Q (A-1)

Spreading monolayers of perdeuterated 1 -alcohols on topof null-reflecting water, their changes in thickness anddensity could be determined using the time-of-flightreflectometer CRISP at the neutron spallation source ISIS.Due to the relatively short length of these chain molecules,we have explored a Q-range up to 0.5 A (with an incidenceangle of 1.5 deg).

Fig. 2 shows the changes in neutron reflectivity occuringat 39 °C for 1-dodecanol and at 55°C for 1-tetradecanol [3].The fitted curves (solid lines) show that the surface area permolecule increases by about 30% at the melting temperaturedue to decreases of both the thickness and the density of themonolayer.

Local dynamics in polymer glasses

Side group and main chain deuterated and fullyprotonated atactic polystyrene of high molecular weight wasinvestigated by time-of-flight and backscattering in a widetemperature range around the glass transition temperature(Т„=375К). In the glass an inelastic low frequency excessscattering over the Debye contribution is observed [4,5]which shows a weak effect on isotope substitution, i.e. isshifting towards lower frequencies for deuteratedphenylrings. The dynamic response changes towards a morequasielastic spectrum at already 200K below the glasstransition Т„. A partial deuteration of the samples allows theconclusion that the phenylring dynamics changes al thesetemperatures. This can be seen from Fig.3, where thecalculated mean squared displacement is shown as afunction of temperature. Clearly the fully protonaled sampleshows higher values of <u~> above about 150K. This has itscorrespondence in the low frequency scattering which isobserved in this temperature regime below an energy

tefradecanol

0 0.1 0.2 0.3 0.4 0.5

Fig. 2: Neutron reflectivity of monolnyers of deuterated fattyalcohols al two temperatures on hoth sides of the 2D melting point(11) CI2D2SOH. (h) C,jD2VQH.

%0.8л

PS-h8;ÔE=l|ieVPS-h8 extrapolationPS-d5; 6E=8u.eVPS-d5;5E=lneVPS-d5 extrapolationPS-h8fromref/6/

0 100 200 300 400 500temperature (K)

Fig. 3: Menu squared displacements for PS-d5 ami PS-h8calculated from the Q-depeiulence of the elastic scattering 141to 2À'1 anil with lj.lv V energy resolution from INK) data.The two straight lines are low temperature extrapolationsof the mean squared displacement. Data for PS-d5 measuredon IN13 ("') are shown for comparison.

COLLEGE 9b

a peraturefthe

transfer of about 1.5 meV. If the temperature is increasedfurther close to T a . then the low frequency relaxationprocess, which is well known tor very different types ofglasses, is observed to set in very rapidly. Thus two differentdynamic regimes are detected in polystyrene.

Another example where the side group dynamics of apolymer could be separated from the main chain dynamics-using partially deuterated samples is polyisoprene.The dynamics of the methyl side group had been detectedfar below the glass transition applying the fixed windowtechnique on IN10 and IN13 |6]. The first decrease of theelastic scattering shown in Fig.4 is ascribed to the methylegroup dynamics and it levels off before, near the glasstransition temperature, a second decrease appears which isrelated to the fast glass transition relaxation process. Modelcalculations for methyl group jump models reveal that only adistributioi! of relaxation times or activation energies,having its origin in the local disorder, can explain therelatively slow intensity decay with temperature.

Flow enhanced concentration fluctuationsin sheared, semidilute polymer solutions

Using light scattering and SANS with various scatteringgeometries (different beam paths with respect to the sheargradient direction) and shear flow geometries (Couette orcone-and-plate), it has been observed by several groups thatthe scattering intensity of a semidilute polymer solution isstrongly increased by shearing the system. Flow enhancedconcentration fluctuations have been found to be eitheranisotropic with respect to the flow direction or to beisotropic. A debate is centred around the question whethershear induces a shift in the cloud point of the solution orwhether the concentration fluctuations in the entangled

100 200temperature (K)

l-'iK. -t: Elastic scattering as a function of temperatureих uhsen'ed on IN10 for differently dettterated polyisoprenes.The first relaxation step corresponds to the rotational dynamicsof the methyl groups and the second step corresponds to the onsetof a fast dynamic process near the glass transition.

polymer system are amplified and distorted by othermechanisms, without a shift in the critical temperature forphase separation.

Figure 5 (page 140) shows one of the results of recentshear experiments performed at the SANS instrument PAXYat LLB 171 with a semidilute solution of perdeuteratedpolystyrene in the solvent di-octylphthalate (OOP) ata concentration 9% w/ w. DOP is a theta solventfor polystyrene at a temperature of Т = 22°C. TheseSANS experiments have been performed at differentshear gradients V in the "strong shear" regime (Weissenbergnumber Wi = у tc » 1, with tc being the longest relaxationtime of the system). Variation of the temperature, as afurther parameter, allowed tuning of the solvent quality;hence, different regions of the phase diagram of the polymersolution were explored, ranging from poor solventconditions at T=15°C in the vicinity of the phase boundary,across the theta region around T=22°C to the good solventregime at T=50°C.

At rest, an azimuthally isotropic scattering pattern isobserved. Under shear, the pattern (see Fig. 5) becomesslightly anisotropic at large momentum transfer q, witha long axis perpendicular to the flow direction. At low q,closer to the beamstop, a pronounced increase parallel to theflow direction leads to a double winged shape of the patternwhich ressembles closely the "butterfly patterns", alsoobserved in deformed gels, rubbers as well as in polymermelts. The effect is increasing with increasing shear.Compared to the measurements in the theta region, it is inthe good solvent regime (T=50°C) smoother but still visible.At temperatures below T=22°C, however, when approachingthe two phase region, a strong isotropic increaseof the scattering intensity is observed which superimposeson the "butterfly" pattern.

Fig. 6 shows the radial intensity distribution,corresponding to the raw data shown in Fig. 5 in directionsparallel and perpendicular with respect to the flow direction.In perpendicular direction, the differential scattering crosssection (d£/dQ)^ of the sheared semidilute solution remainswithin the statistical error identical to the isotropic scatteringat rest ((dl/d£2)jsl)), as being observed already with sheareddilute solutions and with melts. On the contrary,a pronounced increase of the differential scattering crosssection in parallel direction, (d£/di2)n is observed at thelowest q values. In the theta regime at temperatures aroundT=22°C and in the good solvent regime at T=50°C (data notshown here), this increase in parallel direction can beapproximated by a power law of q"1'6. At larger values of themomentum transfer q, however, the intensity in paralleldirection is lower than in perpendicular direction and al evenhigher q the anisotropy vanishes.

A possible theoretical explanation considersdisintcrpenetralion of an assembly of regions of higherconcentrations and regions of lower concentrations in thesolution [8|, as proposed for the description of percolation

COLLEGE 9 b

Fig. 6: Differential scattering crass section dZ/d£2=f(q)of polystyrene in sheared semidilule solution followingfrom the raw data shown in Fig. 5. Evaluation in the directionsperpendicular (±) and parallel (\\) with respect to the flowdirection. The continuous line corresponds to the scatteringof the solution in the quiescent state.

References

[ 1 ] R. Matull, P. Eschkôtter. U. Schellhorn, R.A. Rupp,K. Ibel (1991) Europhys. Lett. 15 (2) 133-137.

[2] R. Heinzmann, U. Schellhorn, R.A.Rupp. P. Bosecke,O. Dial, K. Ibel (unpublished).

[3| J.F. Legrand, B. Berge, A. Renault, D. Bucknell,

J. Webster (unpublished).

[4] K.Linder,B.Frick,U.Buchenau, PHYSICA A201,(1993), 112-114.

|5J B.Frick,U.Buchenau,D.Richter;POLYMER & COLLOID SCIENCE; in press.

16] B.Frick, LJ.Fetters; MACROMOLECULES,FEB. 1994, in press.

[7] F. Boue, P. Lindner, ( 1994) Europhysics Lett.25 (6), 421 (1994).

[8] J. Bastide, L. Leibler, J. Prost (1990).Macromolecules 23, 1821.

clusters of regions of high crosslinking ratio ai.er randomcrosslinking of a semidilute solution, which is well suited topredict the "butterfly" effect in uniaxially deformed swollengels. The deformation in the parallel direction acts as adilution of the high concentration regions (harder) inside thelow concentration regions (softer). These regions may behighly "interpenetrated" in the quiescent state, i.e. theirscreening length Ë; (observable by scattering) is muchsmaller than their maximum size. Dilution, as equivalent forinstance to shear in II - direction, will increase the "visible"size of the clusters. However, the sheared semidilutesolution is entangled but not crosslinked. This is similarto the case where free mobile labelled chains are embeddedin a stretched matrix: "butterfly" effects are observed whenthe matrix is crosslinked, as well as when it is a melt of longchains, which are just entangled. In stretched gels a powerlaw of q at low q is both observed and predicted;it is apparently observed also in the case of the shearedsemidilute solution as described above.

Secretary: Peter Lindner

- DIRECTORATE -

SERVICE

Public Relations

During 1993 the ILL saw the visits of two outstandingpersonalities:

Professor Georges Charpak

The Nobel Prize winner, Professor Georges Charpak,spoke at the joint ILL-ESRF Colloquium on 31 March 1993.He received the prize in 1992 for his invention anddevelopment of detectors in the field of high-energy physics.

Professor Charpak has been a member of the InstrumentSubcommittee of the ILL's Scientific Council.

Since 1959 he has worked at CERN where he inventedthe multiwire proportional chamber. This work waspublished in 1968 and led to the development of differentkinds of multiwire detectors.

In parallel, a technology of 2-dimensional multidetectorsfor neutrons has been developed in collaboration byLETI-ILL (Patent, April 1968, R. Allemand, J. Jacobé,E. Roudaux) followed by industrial production.

A new improvement has been developed at the ILL byusing a technique of micro-strips deposited on glass plates(Patent July 1986, A. Oed), which increases the countingcapacity and the 2-dimensional spatial resolution of suchdetectors.

Dr. Gerhard Stoltenberg

On 15 September 1993, Dr. Gerhard Stoltenberg fromthe Auswartiges Ami in Bonn, accompanied by Hans vonHengstenberg, Generalkonsul der BundesrepublikDeutschland in Lyon, visited international researchinstitutions with German collaboration in Grenoble: the ILL,ESRF, EMBL, IRAM and the High Field MagnetLaboratory.

Dr. Stoltenberg signed the first German/FrenchConvention for the foundation of the ILL on 19 January1967 in his then capacity as Bundesminister fur Forschungund Wissenschaft.

Volker Knoerich, Ministerial-Dirigent in theBMFT/Germany, also took part in the guided tours.

The lunch in the ILL-ESRF joint restaurant provided theopportunity for G. Stoltenberg to meet personalities fromGrenoble public life: Joël Gadbin, Préfet de l'Isère;Jean-Paul Watteau, Recteur de l'Académie de Grenoble,Chancelier des Universités; Alain Nemoz, Président del'Université Joseph Fourier, Grenoble; François Gillet,Directeur du Pôle Européen Universitaire et Scientifique;Joël de Leiris, Maire-Adjoint de Grenoble, chargé desRelations Internationales, des Universités et de la Recherche.

During the press conference concluding his visit,G. Stoltenberg expressed his strong impressions on theeffective and intense scientific collaboration betweenGermany and France and also at the European level in theGrenoble region. He noted that this fruitful collaborationmerits greater support by the German and FrenchGovernments.

As in 1992, the ILL participated in "La Science en fête",initiated by the French Ministry of Education. Manyresearch laboratories from the Grenoble region mannedstands side by side in Place Victor Hugo in the centre ofGrenoble for three days, 4 to 6 June. The ILL-ESRF jointstand was a great success. Directors, scientists and engineersexplained in personal discussions the activities of the ILL tothe public.

During the "Semaine Européenne de !a CultureScientifique" (basically organized by the ESRF) the ILLparticipated in the European Press Day on 23 November, onthe ILL-ESRF-EMBL joint site. An international pressconference was held in the morning followed by guidedtours to the institutes in the afternoon. Several publicationsappeared afterwards.

Bernd Maier, Scientific Secretary, took early retirementin June 1993. Since the first activities of the ILL, he wasresponsible for scientific coordination of the users'programme and for public relations. Assisted by GerryBriggs and later by Herma Buttner he created a wellorganized office. He produced many brochures and leafletsabout the ILL and regularly promoted articles in the press

DIRECTORATE SERVICE

on the scientific achievements of the ILL. The ILL AnnualReports produced by B. Maier were of high professionalstandard and greatly appreciated by the readers. His heartwas devoted to the well-being of the Institut.

Since July 1993, with the new organization, H. Biittner ishead of the Scientific Support Group in the ScienceDivision, which includes scientific coordination.

The public relation activities were taken over byB. Dorner for scientific matters. He remains a member of theTAS Group in DS and is instrument responsible for INI. Asfar as technical aspects and relations with local public-authorities are concerned J. F. Veyrat, head of the Safety,Medical and Health Physics Group, is in charge.

Bruno DornerScientific Secretary

Safety, Medical and HealthPhysics Group

Health Physics

1993 has been another year during which the workof the Health Physics Service has been closely connectedwith the work in the reactor.

Individual Dosimetry monitoring, checking theradioactivity of all the equipment dismantled in the reactor,evaluation of the active items to the radioactive wastedisposal.

Amongst this work, one operation has required the mosteffort from the Service.

• The cleaning and decontamination of the reactorswimming pool so as to provide satisfactory environmentalconditions for personnel working on the new reactor vessel.The results were excellent, so that staff can work normalhours in the pool.

Safety

Various measures have been taken:

• To decrease the number of industrial accidents;

• To follow up the safety of the work on the reactor:preparation of safety plans;

• For the Safety Unit, a major project has beenmonitoring the external and internal painting of the ReactorBuilding;

• Training ILL staff on safety (fire extinguishers,handling, electricity, first aid practice, etc);

• As the Head of Safety. Medical, Health Physicsand Environment (D.SPSE) is now also in chargeof problems relating to the environment, efforts have beenmade to introduce a better system for collecting waste(used oils, metals, papers, etc.).

Joint Works Medical Service

In addition to medical surveillance of ESRF and ILLstaff, the Joint Medical Service has directed its activitiesto an enquiry of staff working on computer screens and risksconnected to conditions of work, particularly back problems.

The Joint Medical Service is fully operational in its newpremises in ILL 17.

Jean-François Veyrat

- SCIENCE -

DIVISION

How is science surviving in the third and lust year of neutrondrought? In normal conditions an ILL scientist often had torestrict his activities because as a local contact he had to dealalso with the instrumental and technical aspects of anexperiment. Now many have found the time to delve deeplyagain into scientific problems, to go back to previousexperiments, to treat more complex data. Results were put inorder and collated. Quite a number changed roles: theytravelled as users to Orphée, ISIS, HMI, Prague,Brookhaven. NIST, Australia, and Japan and came homewith new results. We express our gratitude to those researchcentres which welcomed our scientists for visils or evenlonger periods. A few scientists managed to escape their"neutrons-only" world and got acquainted with otherresearch methods such as synchrotron radiation, muons oreven material characterisation in an industrial environment.Some scientists replaced neutrons by computer simulations.

The sudden neutron drought was of course most dramatic ofall for our thesis students. Without neutrons and with asupervisor who might have left for another continent theysometimes had to pass an independence test. They oftenfound neutrons elsewhere and changed their subjects tosome extent. I am happy to say they all made it.

Recently quite a few were busy tackling the n-body problem,whelher the current reorganisation was a 1st or 2nd orderphase transition, as it shows features of both: it needs energy

but it exhibits critical fluctuations. In the new ScienceDivision, the reorganisation mainly concerns the instrumentgroups which comprise all the experimental scientists andinstrument technicians. These groups are responsible forfurther improvement of experimental methods andparticularly the development, maintenance and operation ofour instruments. Development of experimental techniquesand instruments has always been one of the strong points ofthe Institut, a tradition which we want Io keep alive in thefuture. This effort will be based on both the DPT and DSdivisions. While major instrument projects are completelyhandled within DPT, the initiaiion of studies (PIAFE),smaller projects (Laue Detector and - He polariser) or even abigger project like GAMS5 are dealt with in DS.

The attentive reader may note that the traditional separationof the annual report into reports from colleges andinstrument groups has survived the reorganisation. TheJLL's scientific life will continue lo he organised with aminimum of regulations and a maximum of liberty withinthe colleges. Being in a one-to-one correspondence with thesub-committees, the colleges are also the natural connectionto our user community.

Reinhard Scherm

- D S - SCIENTIFIC SUPPORT

Scientific Coordination OfficeThe office helped in the organisation of several

workshops in 1993, which were held at the ILL. The list isas follows:

Workshop Organisers

"Neutrons & X-raysin the Study ofMagnetism"

Dates 21 -23 January 1993

"Memorial Colloquium"Walter MampeDates 29 January 1993

G.H. Lander,(EITU Karlsruhe),W.G. Stirling, (Keele),C. Vettier(ESRF),J. Martinez (ILL/Madrid),P.J. Brown (ILL)

M. Pendlebury

"Dynamics of DisorderedMaterials II"

Dates 22-24 March 1993

A.J. Dianoux, W. Retry (ILL),D. Richter (Jiilich)

"Quasicrystals"

Dates 2-4 June 1993

C. Janot

"Progress in GaseousMicrostrip ProportionalChambers"Dates 21-23 June 1993

P. Geltenbort

Because of the reactor shutdown the ILL scientists andthesis students had to apply for beam time at other researchcentres. The ILL gave financial support to some70 experimental visits to the following research centres:LLB Saclay (F), LURE Orsay (F), ISIS Didcot (GB), PSIWurenlingen (CH), HMI Berlin (D), GKSS Geesthacht (D),PTB Braunschweig (D), NIST Gaithersburg (USA), BNLBrookhaven (USA), Chalkriver (Canada), JAER/ Tokai(Japan), KEK Tsukuba (Japan). The most frequently visitedresearch institute was LLB Saclay.

Within a special agreement between JAERI (Japan) andthe ILL four ILL scientists were invited to work for severalmonths at the JRR-3M reactor in Tokai. Travel and livingexpenses were covered by the JAERI Foreign ResearcherInvitation Programme.

Joint ILL-ESRF Library

Librarian: Christine Castets

1993 Scientific Literature Budget: 1348.2 KFF,Excl. Taxes

ILL Share : 57.5% = 775.2 KFF, Excl. Taxes

In 1993, the 10 % increase in literature budget as plannedin the "Agreement for the Operation and Maintenance of aJoint ILL-ESRF Library" allowed the library to operate ingood conditions and even to improve the service to users:

• It was possible to maintain the journals previouslysubscribed to, despite the continuing increase in their costs,and even to take out some new subscriptions.

• Book acquisition was increased by 10% comparedwith 1992

• Several CD-ROM data bases could be purchasedand installed.

During 1993, the effort was concentrated on backlogcataloguing expected to be completed in July 1994:3300 new entries were registered thanks to equal additionalhelp from ILL and ESRF.

Allocation of literature costs in 1993.

Serials6.25

Others4.46 %

Binding3.72 %

Books9.23 %

Journals76.34 %

• 1045 books were processed, of which 622 wereadditional copies of existing books:

- 396 books for ESRF Departments or Divisions- 100 for ILL Departments or Divisions- 549 for the Joint Library ( 500 in 1992)

• 900 volumes of journals were bound.

- D S - SCIENTIFIC SUPPORT

A CD-ROM station "libre service" was installed inthe reading room making it possible to load up to a total of12 discs.

This is a major improvement in the service to users sincescientists can now search directly and at any time thefollowing data bases:

)INSPEC-On Disc Physics ( Physics Abstracts),1989-1993. 5 discs loaded permanently

> Medline, 1982- i 993, 14 discs of which 6 loaded) IS1 Science Citation Index, 1993, one disc loaded

The most used is of course 1NSPEC.

Current Contents on Diskette with Abstracts (Physical,Chemical and Earth Sciences) installed on the network since1992 remained a useful tool for current bibliographicsearches.

Publication files of ILL and ESRF were transferred ontothe LORIS/DORIS system of the library.

Publications:

For the II L, 339 publications were received(compared with 600 in 1992).

4 5A 5B 6 8 9A 9B

log94:nal

Publications received in 1993 by subject:

/ - Instruments ami Methods2 - Theory3 - Fundamental and Nuclear Physics4 - Excitations5a- Crystallograpliic Structures5h- Magnetismf> -Liquids, Disordered Materials8 - Biology9a- Chemistry- Small molecules9b- Chemixtrv- Colloids and Polvmerx

Herma Biittner

- D S - NUCLEAR AND FUNDAMENTAL PHYSICS GROUP

Nuclear and fundamentalphysics (NFP) Group

PN1 Fission product separator LOHENGRIN on beamtube H9 (H.R. Faust. G. Fioni, I. Gartshore)

PN3 Curved and flat crystal spectrometers GAMS2/3,GAMS4, GAMS5 (project) on the through-tubeH6 - H7 (H. Borner. A. Williams. R. Oliver)

PFI Cold polarized beam at the end position of guideH53 (J. Last, U. Mayerhoter, R. Bender)

PF2 Ultra-cold neutron source and distribution systemon level D using the vertical guide from the coldsource and neutron turbine(W. Drexel. P. Geltenbort, H. Just)

PN1 Fission product separatorThe installation of the reverse energy dispersion (RED)

magnet, which will provide a substantial reduction of thebackground and an increase of up to a factor of 7 in thecounting-rate of the Lohengrin spectrometer, was completed.The support frame was designed and manufactured. It wasmounted on an air-pad system to provide easy positioningof the magnet and to give the possibility of having accessto the old focal plane.

The exit section of the spectrometer was considerablymodified: the beam tube was shortened by 25 cm,the vacuum valve replaced and two additional diaphragmswere added. In the direction perpendicular to the Lohengrinparabola, the size of the beam can be varied (maximumopening 5 cm) with a rotating cylinder driven by an electro-motor and remote-positioned by a PC. Thirteen shutters eachof them about 3 cm wide and remote-pneumaticallyoperated, give the possibility of sampling the 40 cm of theLohengrin parabola. The combined use of both diaphragmsis essential in the tests of the modified ion-opticsof the spectrometer and for experiments requiring a veryhigh-purity beam.

The experimental area and the data acquisition andcontrol rooms underwent significant improvements: a falsefloor was laid down and a suspended ceiling was mounted toprovide a better working environment. The electronics usedto control the instrument was re-cabled to assure an easiermaintenance.

PN3 Gamma ray spectrometersThe upgrade of the GAMS2/3 spectrometer (Miinchen-

ILL collaboration) is nearly completed. The new opticalinterferometers are assembled and aligned with respect tothe faces of a reference cube. The spectrometer is currentlybeing reinstalled at its original site in level С of the reactor.

dumond doublespectrometers flat crystalGAMS ll/lll spectrometer

GAMS IVD 2 0

doublebent crystalspectrometerGAMSV

source changer source P a ' r spectrometer

Fig. I : Implantation nfllte у-''iiy spectrometers GAMS2/3and GAMS4 tit the Ho ami GAMS? at '.he H7 side, respectively,of the tlimiif-li^oiiif; beam lube.

The 5.8 m DuMond spectrometer GAMS1 will bereplaced by a two-axis focussing spectrometer of focallength ~ 17 m. This spectrometer, GAMS5. is currently underconstruction (see section "projects"). Fig. I showsschematically the intended implantation of the differentspectrometer set-ups on either side of the through-tube.The high-resolution measurements can be complementedby measurement of primary y-ray spectra using the formerpair spectrometer PN4. This spectrometer has been offeredas a CRG instrument.

The two-axis flat crystal spectrometer GAMS4 (NIST -ILL collaboration) is currently stored in the second guidehall (1LL22) where it is kept under running conditions.Currently a new antivibration system is being developed forthis spectrometer at NIST.

PF1 Cold polarized beam facilityIn December 1992 it was proposed to move PF1 from its

old location at H14-2 to the end position of H53 in the newguide hall. This neutron beam had been used before in then-n experiment. After the general layout had been designedthis project was formally accepted in April 1993.

Since then, work has been done on infrastructure detailsof the installation. The new facility not only features anenlarged floor surface for experiments, but in addition,an area for experiment preparation and testing (Fig. 2).Future experimenlers will also appreciate the separationof the experiment electmnics from the physicist's cabin.

At its exit in the EVA cabin H53b h;is an integratedneutron capture flux of MO1 0 n-cm"2-s"' and a cross sectionof 60x100 mrrr. This cross section will be maintainedthroughout a 4 m long Ni extension guide between(he EVA monochromuior and the PF1 polarizer. We hopeto have at least 80% of this flux available toi PFI.

At present there are no supermirror polarizers availablewhich can accept the lull beam cross-section but it is hopedto be able to use two standard size polarizers on lop of eachother. In principle the use of a 3He spin filter would be anelegant method of solving the problem of large area beam

- D S - NUCLEAR AND FUNDAMENTAL PHYSICS GROUP

polarization but the application of thistechnology to neutrons is still underdevelopment.

Work on a focussing device is alsoadvancing. Some 100 silicon strips, each5 mm wide and 70 mm long with athickness of 0.25 mm, were coated witha non-polarizing supermirror. Thesputtering was done in Wurenlingen,Switzerland.

Currently, the second magnet of theformer BILL spectrometer is being usedat the o!d PF1 site to measure the 177Lu13-spectrum. Earlier runs revealed a haloof electrons of arbitrary energy which arescattered on the walls of the inner vacuumpipe and find their way into the detector.This leads to a significant electronbackground around and above the electronenergy end point. To remedy this situationS. Schônert from the University ofMunich has developed a new detectorwhich adds a segmented silicon detectorto the old wire chamber geometry. It isthus possible to measure the energy of an electronin coincidence with a wire chamber signal and to excludeevents where the electron kinetic energy does not correspondto the magnet setting. At the time of writing, December1993, the first data is being taken with the new detectorand electronics set-up.

PF2 The source of very coldand ultracold neutrons

The source of very cold and ultracold neutrons(VCN/UCN) on level D was operated in the context of ILL's"Special Instruments" from its installation in 1985 until thereactor shut-down in 1991. Under the reorganization of theILL in 1993 it became the instrument PF2 and is now one ofthe regularly scheduled instruments in the nuclear andfundamental physics group. Its applications range fromexperiments in particle physics (search for an electric dipolemoment of the neutron, precise determination of the lifetimeof the free neutron) through optical experiments (neutronmicroscopy, interferoinetry) to condensed matter physics forexperiments with extremely high absolute resolutionobtainable with UCN (neV). The high intensity is a result ofthe design of the source that can be seen in Fig. 3 (page 140):a neutron guide (TGV) made of metallic Ni dips with theAluminium entry window into the deuterium of the verticalcold source and transmits neutrons within a velocity rangefrom about 30 to 200 m/s to the experimental floor on levelD. The beam is split into halves: one half supplies a beamof VCN to the experimental floor, the other half is guidedto a neutron turbine. There, VCN are Doppler-shiftedto become UCN by reflections on the preceding blades

Echelle

0 Im 2m 3m 4m 5m

Fig, 2: The plan of a large part of the second neutron guide hall. 1LL22. The unshadedureas at the end position off/if H53 cold neutron guide show the region occupiedby the new intense cold polarized beam facility for fundamental physics called PFI.

of the neutron turbine (690 cylindrical Ni mirror bladesmounted on a wheel structure of 1.8 m diameter movingat a peripheral speed of 30 m/s). The measured intensities atthe respective exit slits were:

VCN density: 0.25 cm'3 (m/s)"3 at 50 m/s

UCN fluxes: 2.6-104 cm"2 s"1 up to v, = 6.2 m/s

and 3.3-104 cm'V ' up to v7 = 7 m/s

These values show that PF2 is the strongest source ofVCN and UCN worldwide. Available for external proposalsare 1 beam of VCN, 3 high intensity beams of UCN ina switch mode and one permanent UCN side beam of lowerintensity. For possible future needs a second beam of VCNand another permanent beam of UCN can be made available.This unique source 1ms been described in detail in ( I ).

During the reactor shut-down the second, curved part ofthe above mentioned neutron guide has been renewed; it hasbeen fabricated by the Teclmische Universitat Miinchen(TUM) under the supervision of H. Nagel. It was assembledand leak tested successfully in autumn 1993 at the ILL andits installation is scheduled for May 1994.

Experiments with direct ILL involvement concerncurrently the neutron lifetime measurements and the neutronEDM measurements:

MAMBO II:

It was shown by the experiments of W. Mampe et al. (2)that UCN storage experiments can supply the most precisevalues for the lifetime of the free neutron. Such experiments

-DS- NUCLEAR AND FUNDAMENTAL PHYSICS GROUP

iilecl

on the decay of the tree neutron give essential informationabout the weak interaction coupling constants gA, gv .A detailed analysis of the former bottle experiment showedthat it should be possible to improve the experimentalprecision from ±3 s to below ±1 s with a more advanceddesign. A new apparatus is therefore being constructed in acollaboration between the TUM and the ILL in the contextof a doctoral thesis (3).

In bottle experiments UCN are stored in a trap ofvariable volume and one counts the number of remainingneutrons as a function of storage time. During storage,neutrons are lost by the decay of the free neutrons and byabsorption or inelastic scattering on the trap walls.Assuming that the losses on the trap walls are proportionalto the wall collision rate the neutron lifetime can bedetermined by an extrapolation to zero of the ratio of wallarea to trap volume. Gravity enters as a correction, as wallelements at different heights contribute differently to thoselosses. Furthermore, it has been shown in the context of thisdoctoral thesis that there exist non-vanishing energytransfers during wall collisions - an effect that may not beexplained fully by mechanical vibrations of the trap walls.

In the new experiment (MAMBO II - Mampe bottle II;see Fig. 4 (page 140) the storage volume is integrated in alarger surrounding pre-s;orage volume. This pre-storagevolume allows the shaping of the energy-spectrum of theUCN before they are transferred into the storage trap. Thedesign ensures furthermore that the UCN-spectra areindependent of the trap volume at the time when the UCNare transferred into the storage volume. The construction ofthe experimental apparatus is nearly finished andexperiments should begin immediately the reactor restarts.

Extensive analytical calculations have led to a detailedunderstanding of this experiment. A Monte Carlo programpackage has been developed in order to describe neutrontrajectories for any geometry which allows the quantitativedescription of phenomena that cannot be treatedsatisfactorily by analytical methods.

It has been shown that with this new apparatus it shouldbe possible to obtain a total error for the neutron lifetime ofabout ±0.8 s, or it may be only +0.6 s - if the loss coefficientcan be proven to be sufficiently temperature independent.

New neutron EDM apparatus:

After an interruption of 8 months, on-site development isnow continuing. Concerning the built-in magnetometerusing '94Hg atoms, the f-number of the ultraviolet lightoptical systems has been improved and the Hg nuclear spinrelaxation time in the polarizing vessel has been increased tomore than 100 s by applying a dotriacontane wax surfacecoating. Following these changes, the aim of having an RMSnoise of les;: than 2 nanogauss for the 3 minute machinecycle magnetic field strength measurements has now beenachieved. The next task is to examine the behaviourof the magnetometer in strong electric fields.

The control of the EDM measuring instrument is beingreorganized so that it employs two PCs running underLABVIEW.

References

(1) Steyerl A. et al., Phys. Lett. A 116 (1986) 347

(2) Mampe W. et al., Phys. Rev. Lett., 63(6) ( 1989) 593

(3) F. Schorr, Doktorarbeit. Technische UniversitatMunchen, July 1993 also: V.V. Nesvizhevski,ILL report 93 VVNO02S

Very cold neutron beams at ILL(Responsible: P. Ageron)

In recent years several different VCN beams have beenused for fundamental physics experiments with thefollowing guides on the cold neutron source (except for theformer SN5).

width height radius cut off À examples of useIcm] [cm] [m] [Â]

TGVextraction

73x2,4

reflectometry

UCN productionin He,, (A=9 A)

neutron electriccharge (A. = 20 A)

interferometer(?L=100A)

Figure 5 shows the measured VCN spectra for thefollowing guides:

SN5 max (on the garland side)

SN5 mean (over the whole section) [ 1 ]

HIS mean [2]

Entrance to the turbine, level D, on the garland side maxat x = 0.2 cm mean at x = 3.7 cm [3]

From these measurements one sees that

• SN5, which is a thermal source, has brightness50-100 times lower than the other guides which come fromthe cold source;

• the vertical guide (TGV to level D) which penetratesinside the cold source is clearly superior for the longestwavelengths (>50-100 Л);

• the H18 guide and, a fortiori, the other cold guides(HI7, H14 or H 53) are superior for the shorter wavelengths(> 10-20 A).

-DS- NUCLEAR AND FUNDAMENTAL PHYSICS GROUP

for the

VCN-UCN spectra at ILL

H I S-a- D VCN max-o- D VCN mean

SN 5 meanD ucnSN 5 max

100wavelength A

FiK. 5: VCN-UCN spectra at ILL. Shown are the measured UCNspectra for the following guides: SN5 max (on the garland side).SN5 mean (over the whole section). H18 mean, entranceto the turbine, level D. on the garland side max atx — 0.2 cm, mean at x = 3.7 cm.

To take VCN from these different cold guides in thefuture, side deviators would be necessary, because endpositions are no longer available for VCN extraction.Options for consideration are:

• deviation, and monochromation with ДАД = 10%

by artificial crystals, i.e., a multilayer film with bilayer

thickness d > 2 x 30 A or mica with d = 10 A. The deviation

oc = 20 Bragg and the selected wavelength A. are related

by К = 2d sin (a/2).

Their reflectivities at long wavelengths are still to beinvestigated;

• deviation with a cut off X» = Vl-7-10"3(for Ni)

by multislit benders (with slit width w and length I).

The characteristic angle is given by:

They could be made like those of the feed guide in themagnetic storage ring NESTOR [5] with many thin glasssheets of thickness = 0.2 mm and length 300 mm bent to aradius as small as 200 mm, separating channels of width = 3 mmso that 1/w = 100. Monte Carlo simulations for the caseA, = 60 A and deviation a = 30° have shown, for an incidentsolid angle of 10"2 steradian, an overall transmission of 60%for natural Nickel coating (R = 98%) and 90% fora supermirror coating (R = 95% in the SM region) whereR is the reflectivity.

Larger 1/w (about 1000) may be obtained if the neutrons

propagate inside silicon wafers coated with nickel

or supermirror, with a length of 100 mm and a thickness

of lOOjJm; the reflectivity of 99% at the interface has been

measured, but the inelastic scattering on silicon becomes

too severe for long wavelengths (k > 20 A) [4].

One can summarize the possible wavelengths in A

selected by these different systems as a function of two

choices for the deviation:

bender:

cut-off wavelength

crystal:selected wavelength

deviation multislit multiwafer multilayer mica

1/w =100 1/w =1000 d = 60A d = ! O A

In conclusion, new Very Cold Neutron beams can be

obtained:

• for long wavelengths (A > 50 -100 A)

with multislit deviators or multilayer monochromator,

on the vertical guide at level D

• for shorter wavelengths ( 10 < К < 50 À )

with multiwafer deviators or mica crystals on the present

or modified horizontal cold guides H17, H18, H14 or H 53.

Hans G. Borner

References

/1J P. Ageron, R. Golub, M. Hetzelt, W. Mampe.

J.M Pendlebury, J. Robson and K.F. Smith. 1977,

Proc. Int. Symp. on Neutron Inelastic Scattering,

vol.1 (Vienna: IAEA), pp. 53-66.

12] P. Ageron, unpublished.

13] A. Steyerl, H. Nagel, F.-X. Schreiber,

K.-A. Steinhauser, R. Gahler, W. Glaser, P. Ageron,

J.M. Astruc, W. Drexel, R. Gervais and W. Mampe,

Phys. Lett. Al 17 (1986), 347.

[4] U. GrUning, A. Magerl and D.F.R. Mildner,Nucl. Instrum. and Mem. A3I4 (1992) 171-177.

[51 Ein Injektionssystem fur einen

Neutronenspeicherring, K.T. Kiigler, Bonn, IR.78.25.

- D S - DIFFRACTION GROUP

onskelesseenes

Diffraction (DIFF) Group

Dl A: High resolution powder diffractometer(1/2 CRG) (J. Rodriguez-Carvajal, A.W. Hewat, P. Cross)

D2B: Very high resolution powder diffractometeron thermal beam H11(T, Vogt, A.W. Hewat. P. Cross)

DIB: Two-axis diffractometer with multidetector on(CRG) thermal guide H22 (C. Ritter. B. Ouladdiaf,

K. Ben Saïdane)

D3B: Two-axis polarized neutron diffractometerwith lifting counter on hot beam H4 (F. Tasset)

CRYOPAD: Cryogenic Polarization Analysis Devicefor Spherical Neutron Polarimetry on IN20(F. Tasset. S. Pujol)

D4B: Disordered materials diffractometer sharingthe hot beam H8 with IN IB(P. Chieux, P. Palleau)

D9: Four-circle diffractometer on the hot beam H3(M.S. Lehmann, C. Ritter, J. Archer)

D10: Four-circle triple-axis spectrometer on thermalguide H24 (G.J. Mclntyre, B. Ouladdiaf)

D15: Two-axis diffractometer with lifting counter(CRG) on the inclined thermal beam (CRG) IH4

(P.J. Brown, M. Reehuis, G. Schmid)

D19: Multidetector diffractometer for proteincrystallography on the thermal beam H11(S.A. Mason, J. Archer)

D20: High-flux multidetector on the thermal beam H11(J. Pannstier, P. Convert, J. Torregrossa)

The new diffraction group is little changed from the olddiffraction group, except that with the reduced ILL budget,instruments DIB, 'ADIA and D15 will be taken out ofservice and hopefully operated by Collaborating ResearchGroups (CRGs). These CRGs will be integrated so far aspossible into the normal activities of the group, and CRGscientists will be given offices next to ILL scientists.However, DIB will continue to be be used for scheduledexperiments until D20 is operational with its new detector.DIA, which is presently operational at Saclay, will return toILL in July 1994, and D15 will be re-installed in the reactorbefore being handed over to a CRG.

Apart from the new D20 detector, other majorimprovements will include the new 2D position sensitivedetector for D19 and the use of the former D19 detector onD10. New focussing monochromators will be available forDIA and D2B, the latter using the new bent wafertechnique. D20 will also have a new pyrolytic graphite

focussing monochromator to provide very high intensity forreal-time experiments. Good progress has also been madewith cryopad-11 which will replace the original cryopad onD3, and with development of the - He polarisation filter (fordetails, see the chapter "Projects").

Shortly after the re-organisation in July 1993, thediffraction group moved from its somewhat isolated positionin the computer building to the first floor of the mainbuilding. Space was also found on the first floor for the newscientific computing group of Jane Brown, with whom weexpect to work closely. For the first time all diffractiongroup scientists were brought together in the same building,while instrument technicians were brought together inILL20.

The first priority of the new diffraction group is ofcourse the re-installation of the instruments; DIB and D10in the guide hall (as well as DIA at Saclay) are alreadyeffectively operational. The instruments in the reactor hallwill be replaced as soon as we have access to that area, withthe major task being the re-installation of D19, D2B andD20 on the HI I beam tube. The re-installation of D3. D9and D4 should be somewhat easier, except that in the case ofD4, the only instrument responsible, Pierre Chieux is leavingunder the early retirement plan. The absence of other staff ondetachment means that there will be only one experiencedscientist per instrument available for the re-installation of allof the diffractometers in the reactor.

A second priority has been the modernisation of thecomputer resources available to the group. All PDP-11control computers are being replaced by (second hand)micro-vaxes to simplify maintenance. Under the Unix plan,three Silicon Graphics Indigo machines have already beenpurchased (one second hand), and by the time the reactoi re-starts we will have similar Unix machines available to all ofthe diffractometers for data analysis. Instrument control willhowever, remain with the micro-vaxes for the present, withall computers communicating through ethernet, which willalso eventually be the link to instrument electronics andmake it easier to change instrument control computers.

The choice of Unix computers was determined by ease ofoperation - the Indigo has a graphic user interface similar toWindows-NT and Macintosh - and by the availability ofsoftware for diffraction data analysis. In particular we havepurchased the CERIUS modelling package from theCambridge (UK) company Molecular Simulations, and alsomake extensive use of the 3D data visualisation package IrisExplorer, for which there are local centres of excellence inEdinburgh and Oxford (NAG). Each of our Unixworkstations operates at about 10 times the speed of theformer central computer, which means that real-time datacollection can now also be analysed in real-time, allowingthe scientist to intervene more effectively in the experiment,rather than simply to collect data blindly.

- D 5 - DIFFRACTION CROUP

As an example of the use of CERIUS, Fig. 1 on page 141shows the structure of a small molecule inside a zeolite cage,together with the neutron powder diffraction patterncalculated for this structure. The molecule can be movedaround within the structure and the diffraction patternupdated almost instantly to reflect the new geometry.Alternatively, the likely positions for the molecule can becalculated using the energy minimization module ofCERIUS. and this can serve as a starting point for theRietveld refinement module. The fast 3D graphics of theIndigo make it very easy to examine complicated structuresand data.

Another example is shown in Fig. 2 on page 141. This isdata from a 'real-time' experiment on DIB. where adiffraction pattern has been collected every minute as thesample undergoes a phase transition on cooling. IrisExplorer has been used to plot the diffraction surface in 3D.and this surface can be spun around with the mouse pointerto find the most interesting features. Other examples ofthe visualisation of 3D electron and magnetic spin densities,position-sensitive detector data etc are given in theCollege 5 report.

D1A High Resolution Powder Diffractometeron Thermal Guide H23

D1A was moved to Saclay as a complete workinginstrument soon after the start of the ILL reactor longshutdown, and will remain there until July 1994. shortlybefore the restart of the ILL reactor. At the same time, theDIA control computer was updated to a micro-vax runningthe MAD diffraction data collection software. At Saclay,D1A was installed on a cold neutron guide, the only suitableposition available, and has been working near the guide cut-off of 2 A. The intensity on the medium (lux reactor is ofcourse several factors lower than it was at ILL, but is stillsufficient for many experiments, especially those onmagnetic structures. In fact, a great many different visitorsmade use of D1A at Saclay under the guidance of JuanRodriguez-Carjaval, a scientist detached from ILL, with theexpert assistance of Peter Cross, an ILL technician. WhenD1A returns to ILL, a new 25-delector/collimator bank willbe installed, and the machine will be half supported as ascheduled instrument and half operate as a CRG.

DIB High Efficiency PSD Powder Diffractometeron Thermal Guide H23

To bring DIB in line with most other ILL instrumenls asregards instrument control and data acquisition, the PDP11computer was replaced by a MicroVax II computer runningunder VMS, and a direct ethernet connection has beeninstalled. The ILL standard control program MAD has alsobeen implemented.

Due to its great success in investigating magneticstructures, phase transitions, kinetic in situ reactions andtexture studies, we think that the future of DIB will be

assured as a CRG instrument with the same field of interest.However, DIB will operate as an ILL instrument until D20is fully scheduled with its new PSD detector.

D2B High Resolution Powder Diffractoron Thermal Beam HI 1

The highest priority for D2B improvement is theconstruction of a new Ge monochromator that will improvethe line shape in the high resolution geometry. The presentmonochromator is a composite of 30x10 mm slicesof squashed germanium, focussing a 300 mm high beamonto a 30 mm high sample. This gives high intensity(K)7 n.cm"2.sec"') at good resolution (1.5xH)~-\ but in thehigh resolution mode (design limit 5x10"*) the peak shape istoo broad and not sufficiently uniform. These defects are dueto variations in both the mosaic spread of the squashedgermanium and in the alignment of the individual slices.A new technique, developed at Brookhaven by Larry Passeland others with the help of Tom Vogt from ILL. uses stacksof thin wafers whose mosaic has been increased by bendingrather than squashing.

The ILL is using a similar technique to produce the newD2B monochromator. However, instead of usingcommercial wafers, as produced for the electronic industry,the ILL is cutting the wafers from a large perfect crystal.The advantage is that our wafers will all be perfectly alignedwith respect to each other, so that the stack of wafers willpermit reflections from any |hhl] plane giving us the usualchoice of wavelengths from the same monochromator. If thewafers are misaligned around their normal, then only thereflection corresponding to this normal can be used, with nochoice of wavelength.

D3B Two-axis Polarised Neutron Diffractometer

As was mentioned briefly in the 1992 annual report,R. Papoular of the Laboratoire Leon Brillouin has madeimportant progress dealing with Fourier inversion of 2-Dsingle-crystal data of limited statistical accuracy andresolution. This has applications to high-Tc magneti/ationdensities. In general, data collected on D3 with the normalbeam geometry compatible with large cryomagnets isseverely resolution limited in the vertical direction.

Recent developments of the Fourier inversion techniquewith the CEN-Grenoble Neutron Diffraction Group meansthat it is now possible to calculate the most probable2-dimensional and 3-dimensional magnetization densitiesfrom such an hybrid set of data see Fig. 3 on page 141.This should offer our users a new systematic way of lookingat D3 data. This calculation is intensive because it proceedsby iteration, but we have shown thai wilh (he new generationof RISC processors it takes only 30 minutes on the besttable-top machine. E. Res.souchc, a long term visitor fromthe CENG helping with the rebuilding of D3B. is workingon this technique with the aim of having it operational atreactor restart.

-DS- DIFFRACTION GROUP

eresl.D20

Cryopad-II

Ordered in August 1992, the new cryostat torCRYOPAD was delivered in February 1993. Designed bySerge Pujol it has a liquid helium autonomy of one week andits most spectacular feature is the 19 cm diameter roomtemperature RT-bore. large enough to host most sampleenvironments. The two niobium Meissner shields wereordered and delivered in July to be mounted and testedsatisfactorily at low temperature in September. Using asensitive Gaussmeter in the RT-bore we could verify for thefirst time the shielding efficiency of these opened cylindersagainst an axial magnetic field. We are happy to say that itmatches the design calculations made in 1992 by Luc andMichel Thomas.

Further calculations were made this summer usingANSYS in order to establish the design for the precessioncoils which are to be installed in the annular space betweenthe two shields. This original calculation of a magnetic coilconfined in a Meissner shield environment, which imposesspecial limiting conditions for magnetic induction lines, hasbeen the subject of a stage "Mailrise Sciences elTechniques" for Ivan Neyret. In the compromise made, thesimplicity of the device and ease of use was given highpriority, to little detriment of performance. The resultingsuperconducting coil was ordered in October and will bedelivered in February 1994.

The Mu-metal shield needed to cancel the earth's fieldduring cooling is being manufactured. In the mean lime weare studying a new design for the magnetic guide-fieldsoutside the cryostat (the so-called nutators) since they haveto provide good magnetic confinement, a requirement due lotheir proximity with the vertical opening in the zero-fieldsample chamber.

We hope to have CRYOPAD-II ready for neutron testsand calibration by summer 1994 when the IN20 hostspectrometer is back in operation.

D4 Disordered Materials and Liquids Diffractometeron hot beam MS

After the completion of the new position sensitivedetectors on D19 and D20, the next priority is for a largeangle PSD on D4. The choice of construction technique willdepend on the results with D20, but already plans have beenmade for a modular PSD consisting of eight individual PSDelements. These future developemcnls will have to await thenew instrument responsible, since unfortunately PierreChieux, the father of liquids diffraction at ILL, is leavingunder the early retirement plan. Because D4 time-shares abeam with INI, and counts as only half an instrument, wecan appoint only one scientist in this area. The change overof instrument responsible will therefore be difficult.

D9 Four-circle diffractometer on the hot beam H3

The instrument is scheduled to be ready for the start ofthe reactor, and the assembly is planned for late spring.During the complete reactor shut-down the instrumenttechnician J. Archer, was employed at the Hahn-MeitnerInstitute, Berlin, and at his return late in the year the firstpreparations began. The instrument itself is at presentlocated in the guide hall, while the monochromalor housingand the electronic cabinets were kept near their originallocations. A few parts of the equipment have been on loan,particularly the micro-Vax controlling the instrument andvacuum-shield furnace, but they will all be relumed beforeMarch 1994. The only outstanding part of the preparalion isthen a recabling of the monochromalor, which is nowunderway.

At the startup D9 will therefore be equipped withlemperature control units going from 15 К to about 1100 K.Il will also, as before, have a small 32 by 32 pixel posilionsensitive detector. The monochromalor for the start-up phasewill be the tradilional Cu(220) in transmission, but it isplanned as quickly as possible to continue the short-w a v e l e n g t h tes t s of a hori/ .ontal ly curved Bemonochromator that were under way precisely at the time ofthe reactor shut-down.

D10 Four Circle 3-Axis DifTractometeron thermal guide H24

The main advantages of D10 for diffraction andspeclroscopic studies are its excellenl q resolution due to itslocation on a neutron guide and Ihe small mosaic spread ofthe monochromator, its very low intrinsic background,full 3-D access in reciprocal space, temperatures from 1.6Kto 900K, optional energy analysis, either lo reduce Iheinelastic background or to study inelastic features (still withfull 3-D access), the easy change of instrument configurationduring an experiment, and strong sample table to supportheavy furnaces and cryostats.

The typical applications are to studies of 'conventional'crystal and magnetic structures, of phase transitions, ofincommensurate structures, of quasi-elastic scattering(Huang and critical scattering), of diffuse scattering, ofnovel materials such as quasi-cryslals and multilayers, andof inp'astic scattering.

During the reactor shutdown the new more-robusico-rotation turntable has been installed. This turntable cansupport either the new offset open ^-circle, or ihe new fullyautomated tilt stage for heavy furnaces, pressure cryostatsand cryomagnets. The co-axis has direct encoding wilh anabsolute error of less than 0.004°, small enough to take fulladvantage of the excellent resolution of DID. The crystal-orienting drives are now all equipped with five-phasestepper motors which are virtually resonance free and allowmuch faster and more accurate positioning. The automationof the double-tilt singe means that, if the furnace or cryostatpermits it, several layers of reflections can be accessed under

- D S - DIFFRACTION GROUP

computer control. The offset ^-circle can accommodate thenew DIG four-circle dilution cryostat built by S. Pujol.Under O.IK has been obtained routinely independentlyof the setting for %. A very clear advantage afforded by thiscryostat is that it can be used in the same manner asthe previous 4He cryostat at temperatures above 1.6 K.We eagerly look forward to using it in anger in 1994!

D10 is thus in very good shape to shoulder the load ofthe single-crystal diffraction experiments immediately afterthe start-up especially before D9 and D19 come backon-line. It is therefore not planned to make further changesto D10 until then. Eventually though, the present D19position-sensitive detector will be installed on DIG toimprove efficiency of structural data collection andmeasurement of diffuse scattering.

D15 Two Axis Diffractometer with Lifting Counteron inclined thermal beam IH4

DI5 will become a CRG instrument from the restart ofthe reactor, but ILL will first re-assemble it and the platformon which it sits. DI5 has been a unique instrument for thestudy of crystals at very low temperature; it is the onlymachine which can accommodate very large cryostats andmagnets and still collect 3D data using its lifting detector.It is ironic that at the same time as D15 is being taken outof service, new instruments largely inspired by D15 arebeing constructed at other reactor centres such as Saclay.However, since several groups from all 3 associate nationsshowed strong interest in continuing to use D15, it is hopedthat it will not be too difficult to support it as a CRGinstrument.

D19 High flux multidetector diffractometeron the thermal beam Hll

DI9 is a four-circle single crystal diffractometer which atstartup will incorporate a larger (64°x20°) position-sensitivedetector (PSD). D19 works best in the wavelength range1.2 to 2.4 A and is most efficient for larger unit cells(>IO À on edge), but even for single reflections will giveimproved intensity integration because of the detector'sspatial resolution of 0.2°x0.2°.

As in the past. D19 will share the Hll beam with thepowder diffractometers D2B and the upgraded D20, makingthe HI 1 beam without doubt the most productive at the ILL.D19 has the following features: high resolution due to amaximum monochromator take-off angle of 90°; a choice ofup to four monochromators by rotation about a vertical axisof an ILL turret monochromator mount (being re-built sothat it no longer interferes with D20's beam); verticalfocussing of the beam for graphite and Ge monochromators;a C-shaped Huber Eulerian cradle on which a 2-stage I5KDisplex cryorefrigerator is routinely mounted. A Munichmirror furnace has also been used by T. Vogt and Z. Mursicup to 2500K.

The old vertically-mounted high pressure (8 atm He)multiwire "banana" detector is set symmetrically about theequatorial plane, with the sample at the centre of verticalcurvature. The detector rotates on a y-arm (7=26 in theequatorial plane), on air cushions. The combination of anEulerian cradle and a large position-sensitive detector allowsdata collection with a choice of geometries. Mostexperiments have been performed with normal beamgeometry, and peak integration is usually by a learnedvolume minimum variance method. The availability of awider PSD (20° rather than 4°) will further increase therange of single crystal diffraction experiments possible withthermal neutrons. Typical in the past were studies on phasetransitions in multi-domain samples, human haemoglobin,organic molecules on the lysozyme surface, helium singlecrystals, acetylene polymers, liquid crystals. Vitamin В12,and a number of cyclodextrin complexes. In order tomount the detector on D19, substantial modifications arebeing made to the detector support, and new shielding isbeing built. This is necessary because the radius of verticalcurvature of the new detector is 60 cm, compared with115 cm before. For most experiments - all except those withvery small unit cells, which would more logically be run onD9, D10 or D15 - the new PSD will give a real gainin efficiency of up to a factor of six. For the experimentsfor which D19 is primarily designed i.e. diffraction fromsingle crystals (or fibres) with larger unit cells, the largegain in solid angle will lead to more extensive data setsin shorter times.

Electronics and software modifications to read the extrapixels (320 * 100, compared with 512 * 16 before) will bemade for the 1994 start-up without change of philosophy.At present D19 is controlled by a dedicated Microvax.The diffraction data are displayed and analysed on aVaxstation 3100 close to the instrument. Programs such asG.J. Mclntyre's MULPLT for 3-d displays of raw data, andfairly complete program systems, such as that implementedat D19 for fibre diffraction by the University of Keele group,run comfortably on the Vax-station. The change from thesecomputers (under VMS) to a Unix work-station will bemade after the reactor restart with the benefit of experiencefrom other diffraction group instruments. This will allow usto commission the new detector - and compare it with theold one - and gain extensive experience vith it beforechanging computers.

D20 High flux multidetector on the thermal beam Hl l

(see the contributions of the Projects and TechniquesDivision to this Annual Report, partly under Constructionof New Instruments, and partly under Multidetector Group)

The delay in the construction of the 160° PositionSensitive Detector is mainly due to the departure to theESRF, at the end of 1992, of our technician M. Berneron,who had made most of the developments for the bananaconstruction, and had the expertise for the realisation ofsome critical parts in the detector. He has been back at ILL

99 100

-DS- DIFFRACTION GROUP

since October 1993. The detector is now ready to bemounted after some adjustments to suppress instability in thegas amplification.

The 52 pieces of the new HOPG monochromator areat ILL and have been tested with neutrons and X-rays.The mechanical support for the 4x13 elements of thisfocussing monochromator is currently under study and willbe available in mid-1994.

The data acquisition system is complete and operationalexcept for the synchronisation module. A Silicon Graphicscomputer has been purchased for the control and dataanalysis of D20.

The 1994 reactor cycles will be used for instrument testsand commissioning experiments. The diffractometer isexpected to become available for external users in the firstmonths of 1995.

Alan Hewat

References

[ I} R.J. Papoular and B. Gillon, Neutron Scattering DataAnalysis. Rutherford Appleton Lub. 16 March 1990.

[2| RJ. Papoular, E. Ressouche, J. Schweizerand A. Zheludev(1992).

[31 R.J. Papoular, E. Ressouche, F. Tasset,ILL Tech. Rep. 93PA01T (1993).

- D S - LARGE SCALE STRUCTURES GROUP

Large Scale Structures (LSS)Group

Dl I Small-Angle Scattering DitTractometer on the coldguide H16 (P. Lindner, L. Vuillard, K. Ibel,A. Polsak)

D16 Four-circle Diffraclometer on cold guide H15(J. Zaccai (IBS). V. Rodrigue/,)

D17 High Resolution Small-Angle Scatteringdiffractometer and Ret'lectoineter on the cold guideH17 (H.-J. Lauter, P.Timmins)

DB21 Diffractometer for very large unit cells on cold guideH15 (E. Pebay-Peyroula (IBS). C. Wilkinson (EMBL))

D22 New Small-Angle Scattering Diffractometer on coldguide H512 (R. May, R. Oeser. K. Ibel. R. Gay)

Laue detectorCollaborative project with EMBL and FreieUniversitiit, Berlin (M. Lehmann),see "Small Projects in DS

The Large Scale Structures group was created as partof the reorganisation of the ILL on July 1st 1993.It comprises the above listed instruments which cover a widerange of science from physics through materials science andchemistry to biology. The common theme is the studyof particles or density fluctuations on a scale up to hundredsof nanometres.

We are particularly fortunate in the group in that noneof the instruments has been dismantled for access tothe reactor. We are therefore in a good position to provideworking instruments immediately the reactor restarts.The past year has been taken up with small improvements tothe instruments and their preparation for the start-up. Threedevelopments are of particular note. The new small-anglescattering instrument D22 is in the final stages of completionand after a short commissioning period should be availablefor users in the second user cycle after the reactor start-up.During 1993 a project was initiated by J.-B. Suck for placingDI6 and D17 on straightened versions of the guides H17 andH18. This is primarily to increase the flux of 3 - К) Лneutrons on DI7 and hence to facilitate its conversion intoa reflectometer. Although it has not yet proven possibleto fund this project, studies are continuing with a viewto implementing it in the future. Finally, very importantadvances have been made by EMBL and ILL in thedevelopment of detectors for use in a future Laue-diffractometer. For details see the chapter "Projects".

As a first step in the conversion to UNIX the grouppurchased a Silicon Graphics Iris Indigo R50XZ computeraccompanied by the graphics software "Explorer". A furtherUNIX machine will be purchased in 1994 in preparation

for the restart of the experimental programme, ensuring thatdata treatment facilities will be available for some timeunder both VMS and UNIX.

We are all waiting anxiously for the reactor to restart andto be able to use and make available to outside users ourrange of new and improved instruments.

Dl 1 Small-Angle Scattering Uiffractomcteron the cold guide H16

A major change at Dl I in 1993 has been the replacementof the old CAMAC electronics by VME. The hardware hasbeen successfully installed and tested, the instrument controlprogram is currently being completely revised.

A further improvement is the motorisation of the 2()mcollimation guide section: all collimution sections at Dl 1 arenow operated by motors and are under computer control.Two more Cd sheets as attenuators have been installeddirectly after the .selector position. Dl 1 now has a choiceof three attenuators, with attenuation factors of = 1/300,I/I 100 and 1/2700 respectively. The process controllerof the compressed air pistons which place the chosenattenuator into the beam is connected to the instrumentcomputer via the VME system.

A common security system for the three Dll selectors(Adèle: ДА/Л = 4(W<. Brunhilde: ДА/А. = 9% and Constan/.e:ДА./А. = \()'/t ) has been installed. The "standard" selectorafter the restart will be the new light weight 10% selector"Conslanxe" made from composite material. All selectorsare now driven by AC motors which themselves arepowered by a common, new REFU 317. Changing theselectors will become a rapid and smooth operation in thefuture as only one cable is used: each selector is identifiedby an individual plug to which the standard cable isconnected. The selector speed will be changed by a controlprogram which directly addresses the REFU amplifier.

The optical sample alignment system has been furtherimproved by installing a compact small laser together with ahalogen lamp. The light beam is reflected from a neutrontransparent silicon wafer into the path of the primary neutronbeam. It will be operated by a switch at the sample positionthus avoiding opening of the collimation section in thechopper casemate.

Further improvements before the restart are in progresswith respect to the sample environment. In particular, a newsample table with a motor driven lifting device and standardrack plates for common use on the sample changers of D11,DI7 and D22 are under construction.

1)16 Four-circle Diffractometer on cold guide His

D16 is in the first group of ILL instruments to bescheduled when the reactor restarts next summer. It is stillone of the very few neutron diffractometers in the world thatallow very good Q-re.solulion over a wide Q-range forstudies of crystalline or partially ordered systems with large

-DS- LARGE SCALE STRUCTURES GROUP

unit cells. By February 1994, the instrument will be in fullrunning order. A number of small but importantimprovements have been carried out; a complete recablingof the instrument, checking and where necessary, replacingmotors, an overhaul of the electronics and tuning of themultidetector. Work is in progress on the monochromatoraxis - a re-designed carriage mount will be aligned tofacilitate wave-length changes during experiments.

D17 High Resolution Small-Angle ScatteringDiffractometer and Reflectometeron the cold guide H17

D17 has undergone a series of small improvements in thepast year in preparation for the reactor start. A new powersupply has been installed for the velocity selector which willbe under computer control. An improved alignment systemis under construction and new attenuators, similar to those ofD17, have been installed. The instrument will restart in thesame configuration as it was at the reactor shutdown. Thus itwill run as a small-angle spectrometer and as a reflectometerfor experiments appropriate to its long wavelength. In themedium term, after the commissioning of D22, theinstrument will be optimised and used predominantly forreflectometry. The first step in this direction is to makeavailable the shorter wavelength "garland reflections" whichare present in a narrow beam close to the wall of the guide.This will require an improvement of the translation of thewhole instrument and the installation of a multilayermonochromator option. In a later phase it is foreseen tostraighten the H17 and H18.guides in order to produce agreatly increased flux of 3 - 10Â neutrons.

DB21 Diffractometer for very large unit cellson cold guide H15

DB21 is a low resolution diffractometer used forexper iments of biological interest . Biologicalmacromolecules, i.e. proteins, assemblies of proteins withnucleic acids such as viruses or ribosomes, are objects oftypical size varying from 50 to a few hundred Angstroms.Low resolution for these experiments means less than 10 A.A suitable wavelength of 7.53 A is obtained with apotassium intercalated pyrolitic graphite monochromator.The previous monochromator was broken at the reactorshutdown. During 1993 new monochromators were made byP. Touzaint at the "Ecole d'electrochimie". A 2 mm thickHOPG was purchased from Union Carbide and then slicedin three parts. Two of them have been intercalated withPotassium (KC8 intercalation) and then pressed to reducethe mosaicity which increased during the intercalationprocess. The first one has been tested with neutrons at Siloe(P. Flores) and with gamma-rays at ILL (A. Escoffier),it showed a mosaicity of 1.7°. The second was pressed at ahigher pressure and tests are currently underway at Saclay.The third monochromator will then be intercalated andpressed according to these results (a suitable mosaicitywould be less than 1°).

In addition to the usual type of experiments, there is ademand for increasing the resolution to about 6 A(determination of domains with intermediate degree ofordering ). This would require another monochromatorselecting a wavelength of 4.5 A (standard HOPG). In orderto change the wavelengths between two experiments easilywithout closing the neutron guide, an automaticmonochromator changer has been designed and built(G. Schmidt). It will be installed as soon as the electronicwork is ready.

The critical point of the instrument is the detector: forlong counting times (typically one data set is collected in aweek or longer), it is very important to have a good stabilityof the detector. This stability is becoming increasinglydifficult to maintain due to the ageing of the photo-multipliers. For this reason a multiwire 3He detectorhas been designed (J. Jacobé) having a similar resolution(1.8 x 1.8 mm) and an overall size of 20 x 20 cm.Preliminary tests at low He pressure have been carried outsuccessfully and tests at nominal pressure will be carried outin the near future.

D22 New Small-Angle Scattering Diffractometeron the cold guide H512

1993 was a year of small, but important, steps forwardfor D22, which visibly turned into a usable instrument.

The 1 x 1 m detector with 16K pixels of 0.75 x 0.75 cmfrom CERCA, delivered just before the beginning of theyear, was installed in D22's vacuum beam tube of 2.5 mdiameter and 20 m length. It was subjected to first testsusing an AmBe source which allowed us to define the axesin the memory and showed that all of the detector electrodesare counting. The final adjustment of the amplifier gainsrequires reactor neutrons. The pressure, humidity andtemperature detectors in the rear of the detector were

Fig. J.' Schematic view of the new Small-Angle Scatteringinstrument D22 showing details of the velocity selector,sample position and detector.

- D S - LARGE SCALE STRUCTURES GROUP

connected to a cabinet which was added to the alreadyexisting industrial process controller dealing with thecollimation and vacuum-pump supervision.

The last mechanical items were mounted in the courseof the year 1993. This concerns the attenuator disk, equippedwith new mechanics and with 3 different attenuator plates,the box containing antiparasitic apertures of different size aswell as the tube which connects the latter with the end of thecollimation system and which carries the laser and halogenlight serving for alignment. The attenuator plates have88 holes each with 0.1 mm (in 0.25 mm Gd), 0.2 mmand 0.4 mm diameter (both in 1 mm Cd), and are expectedto reduce the neutron flux about 5000, 1200 and 300 times,respectively. The sample table equipped with an electricpiston, an ХУФ-1аЫе and the sample changer were installedin front of the detector entrance cone. Two prototype sampleracks are under test.

The Dernier velocity selector, turning at a maximalspeed of 28,300 rpm for neutrons of 4.5 A at a resolution(ДАМ.) of 10 % (FWHM), was installed on a translation androtation table in its "casemate", where it was tested oncemore successfully, together with its independent vacuumpumps. Devices for monitoring its vacuum, vibrations andtemperature were also connected to the industrial processcontrol system.

All encoded movements were cabled to the VME dataacquisition and shaft-control electronics by the ILLelectronics group. With the exception of the four-paneentrance aperture, all of these movements can be controlledby the instrument computer, a Vaxstation 3200. which isinterfaced with the process controller and with a PCcompatible running the graphical supervision programInTouch (under Windows). The instrument control programSAS (compatible with that of Dl I and DI7) was furtheradapted to the needs of D22 by K. Wotschack before he leftthe ILL for early retirement in summer. First dummyexperiments moving the detector in the tube and countingneutrons from the AmBe source were carried out andshowed where small modifications to the control programare necessary. The instrument will be fully operationalfor the second scheduled user cycle after the start-up.

Chemistry and Biochemistry Laboratories

Since the reorganisation of the ILL the chemistryand biochemistry laboratories are under the responsibilityof the Large Scale Structures Group.

Chemistry Laboratory(P. Lindner, P. Chenavas, M. Romero)

The ILL maintains a main chemistry laboratory onthe second floor of ILL20 as well as a smaller laboratoryin the neutron guide hall next to the small angle scatteringinstrument Dl 1. Whilst the facilities are foreseen mainly forvisitors' sample preparation they are also used by in-housescientists. As well as an extensive range of chemicals andsolvents, equipment sucn as glove boxes, furnaces, an I.R.spectrometer and a density meter are available. Full detailsof facilities may be obtained from the engineer-in-charge.Mile P. Chenavas.

In 1993 the laboratory was also used by ESRF staff anddiscussions are taking place with a view to the ILLparticipating in the rather more extensive facilities beingbuilt up in the ESRF main building.

Biochemistry Laboratory(L. Vuillard, P. Chenavas, P. Romero)

The ILL also maintains a small biochemistry laboratoryon the second floor of ILL20. for visitors to carry out lastminute sample preparation. It is also used by in-housescientists to support their own research. Standard equipmentincludes a UV spectrometer, a fluorimeter, gel filtrationapparatus and chromatography equipment. Moresophisticated equipment, such as analytical centrifuges,is available to ILL users in the EMBL laboratories. In 1993the EMBL has been making plans to extend the ILL20building to provide more laboratories which will beavailable to ILL and to ESRF biological users.The extension is expected to be completed in late 1994or early 1995.

Peter Timmins

-DS- THREE-AXIS SPECTROMETERS GROUP

Three-Axis Spectrometers(TA$) Group

INI. INFB 3-axis and Be-filier spectrometeron the hot source beam lubt H8(B. Dorner and P. Palleau)

INS 3-axis spectrometer on the thermal beam lubeH10 (J. Bossy and D. Puschner)

IN 14 3-axis spectrometer on the cold guide H53on the hori/ontal cold source(R. Currat. S. Bramwell and A. Brochier)

IN2(! 3-axis spectrometer lor neutron polarizationanalvsis and spin-echo option on the thermalbea .1 tube H13 (J. Kulda. T. BaumbachandC.M.E. Zeyen)

The above instruments are all located in the reactor hall.Three out of four have been dismantled, between October1991 and February 1992. in connection with the work on thereactor beam lubes. Most of the instrument parts were storedeither in the reactor hall itself or in the new guide hall.The dismantling of the IN 14 spectrometer, also locatedin the reactor hall but looking at the horizontal cold source.was under discussion for some time but eventually wasavoided. The instrument, including its heavy primaryshielding, was not affected by the work on the upstreamguide and on the leactor structures. It will thus be readyfor neutron tests at reactor start -up.

According to current plans, the reassembly of INI andINS is to take place in early spring, after the correspondingbeam tubes have been remounted. Additional delays areforeseen in the case of IN20, following the decision to usethe H13 beam tube as a reactor vessel vibration test site,during the second half of June.

A limited programme of instrument development andupgrading was pursued during the shutdown. The mainitems in the programme are listed below.

The upgrading of the control electronics on INI and IN8was budgeted in 1992 and 1993. All parts have now beendelivered but the completion dale of the project has recentlybecome uncertain due to technical manpower reductionscompounded with the unexpected departure of R. Taffut,the electronics technician in charge of the project. Work willcontinue throughout the first half of 1994.

A modification of the IN 14 monochromatic beamgeometry, aimed at reducing the inonochromutor-to-samplcdistance, is proceeding satisfactorily. The secondary beamshutter and the Soller collimator (or polarising bender)support arc now integrated into the primary protection.Mechanical assembly and electronic adjustments are plannedfor Jan/Fen. 1994.

The 3-axis spectrometer control program, the so-calledTAS program, is being entirely rewritten on the basis of theMAD routines, a well-supported ILL standard system.The program includes a CAMAC electronic library to beused on ?N 14, IN20, IN3 and IN 12 as well as a VME libraryfor IN 1 and INS. The user interface and data file format willremain essentially unchanged. The first version of the newTASMAD program was produced by Ph. Blanchardin Dec. 1993 and is currently under test on the IN 12 jiVaxcompute r . The depa r tu re wi thout r ep l acemen tof Ph. Blanchard at the end of 1993 introduces uncertaintiesand delays for the final completion date of this project.

Another long-overdue project is the replacement of thePDP11 instrument computers by more modern, network-compatible machines. The choice was made to installDEC-Alpha stations 3()()0-3()OL on INI, INS and IN 14.A more powerful version is foreseen for IN20, whereadditional computing capacity is required in the spin-echomode of operation for on-line magnetic-field profileoptimization. The new machines are expected to open newpossibilities for on-line data evaluation and interactiveoptimi/alion of the measurement parameters.

In addition to the four instruments in the reactor hall, twoother three-axis spectrometers are located in the guide hall:IN3. on thermal guide H24 and IN 12 on cold guide H142.Both are now included in the list of instruments proposed forCRG use. In preparation for the reactor start-up, a substantialamount of mechanical and electronic maintenance work wascarried out on each of the two guide hall instruments. As aresult. IN 12 is now fully operational while additionalelectronic maintenance work is still re'. ...'ed on IN3. Withregard to radiological safety, both instruments have beenre-equipped in order to meet the new ILL safety standards.

Problems have developed v/ilh the group's 6Tcryomagnet during operation at LLB-Saclay. Systematicquenching is observed m the 4-6T range when the magnet isfirst cooled after a room temperature warm-up ("training").The magnet is presently under test at ILL in order to identifythe origin of the problem. A decision to send the magnetfor repair, or to use it as it is, will follow shortly.

A number of projects or possible improvements have notbeen addressed due to manpower and budgetary constraints.One such project is the rebuild of the IN8 primaryspectrometer, the design of which was dictated by existingspace limitations at the time of construction. With theimplementation of the HI I project in 1984, these limitationshave been relaxed, and a simpler and more efficientspectrometer geometry will now be possible. A detaileddesign study has been included in the 1995 group budgetrequests.

Another important project is the redesign of the IN20polarising Heusler monochromator, in order to extend theuseful incident energy range of the instrument to higherenergies. A preliminary study underlined the difficulties

-DS- THREE-AXIS SPECTROMETERS GROUP

associated with the very limited space available in themonochromator housing. Obviously, the project becomesmuch more costly if the primary protection has to beredesigned. On the other hand, the recent progress achievedwith the 3He polarising filter technique (see chapter"Projects"), indicates that this latter technique may becomecompetitive in the not-so-distant future. When this occurs,the Heusler crystal may be replaced by a non-polarisingcrystal with good second-order discrimination andcomparable lattice spacing , such as Ge( 111 ) or Si( 111 ).

Another area where important developments can beexpected concerns the use of elastically bent perfect crystals(as opposed to plastically deformed mosaic crystals) asmonochromator or analyser. J. Kulda has been active in thisfield for many years, in collaboration with groups at PTBBraunschweig, NPI Rez (Prague) and more recentlyat JAERI (Japan). His report on recent tests on a seriesof elastically bent silicon crystals is included below.

Elastically deformed perfect crystals and crystals witha lattice spacing gradient are generally recognized assuitable candidates for focussing monochromator or analyzerapplications, thanks to the fact that the beam propagation inthis case is deterministic (the beam trajectories can becalculated for known strain fields). Up to now theexperimental as well as theoretical investigations in thisdirection have concentrated mostly on silicon whichis available in perfect crystal quality for any required sizeand orientation and exhibits, thanks to its covalent bonding,an excellent long term mechanical stability under appliedloads. Its main disadvantage is the rather low scatteringlength density, which can, however, be compensated forby increasing the diffracting volume, thanks to the lowbeam attenuation.

A series of test experiments has been performed atdifferent neutron facilities (PTB Braunschweig, JAERI, NPIRez near Prague) to assess the performance of elasticallybent perfect Si monochromator crystals in comparison to themosaic ones (PG, Cu, Ge) [I]. In most cases both directneutron beam flux delivered at sample position and powderdiffraction spectra with a suitable standard (АЦОз, Si) wererecorded. Horizontal focussing was suppressed with Sicrystals by rather tight collimation (20'), quite large bendingradii (-15 m) and beam cross-sections of about 20x20 mm2

at the sample position, in order to maintain equal conditionsfor both types of crystals. Typical results of a comparisonbetween Si(331) and Cu(220) - both having dhk|=l.25A -and between Si(422), Si(511) and Ge(5l 1) - dhk|=1.05A -are displayed in Fig. I (a) and (b), respectively.

In general the presently available Si crystals providefluxes a factor 2-3 lower than good Cu and PGmonochromators (for reflections with similar d^t).As expected this disadvantage diminishes rapidly whenever

-§2000

"~1000

Cu 220Si 331 2x5mmSi 331 1x5mm

0.8 0.9 1.0 1.1

MA]1.2 1.3

2000Ж

§ 1500

о^1000

-Si 422 2x5mm-Si 511 IxSmm-Ge511 ILL-Ge511 BNL

00.75 0.80 0.85 0.90 0.95 1.00 1.05

Fig. I : Directly measured output fluxes (scaled by cot6 to accountfor differences in wavelength resolution) of mosaic Си. Geand i>f elastically bent Si (5mm single plate and 2x5 mm sandwich}monochnnnator crystals with d/,f-/=l.25A (a) and with d/,y~l.05A (b).

focussing into a small volume in real and/or reciprocal spaceis required. Silicon also becomes a competitive candidatewhenever Я/2 suppression is important: its performance isabout equivalent to that of plastically deformed Ge crystalsof the same thickness, while the excellent homogeneityand reproducibility of the elastic deformation and low costof silicon single crystals should be an advantage. These testsare to be continued at ILL after the reactor restart.

Roland Currat

References

111 J. Kulda, V. Wagner, P. Mikula and J. Saroun, Nucl.Inst. Mem. A 338, 60(1994).

- D S - Т I M E-OF-F L I G HT AND H I G H RESOLUTION CROUP

Time-of-Flight and HighResolution (TOF/HR) Group

IN4C New TOP spectrometer w:th a BriJlouin optionon the thermal tube H12 (project) (H. Mutka)

IN5 Multichopper TOP spectrometer on the cold guideH16 (G. Kearley, S. .enkins)

IN6 Focussing TOP spectrometer on the cold guideHIS (A. J. Dianoux, S. Jenkins)

IN 10 Backscattering spectrometer on the cold guideH15(J. Cook, P.Joubert)

IN 11 Spin-Echo spectrometer on the cold guide H i 41(B. Farago, E. Thaveron)

IN 15 High resolution spin-echo spectrometerfor long wavelengths on the told guide H511(project) (C. Lartigue (CNRS-Grenoble))

IN 16 New backscattering spectrometer on the coldguide H53 (project) (B. Frick)

D7 Diffuse scattering instrument with polarizationanalysis on cold guide H15(O. Scharpf, I. Anderson, A. Murani, R. Rebesco)Group Engineer: J.F. Barthélémy

Several members of the Group have spent a sizeable partof their time at other laboratories: I. Anderson spenttwo months at PSI at the beginning of the year. Since thereorganization, his position is now in the Projects andTechniques Division, but he is still co-responsible of D7.B. Frick came back from NIST in August and B. Farago hasbeen half the time seconded to LLB. J. Cook left on March1st for NIST where he will spend a year.

The TOF/HR group has acquired a Silicon Graphics IRISIndigo R4000 workstation as part of the UNIX plan. Thisworkstation is under the supervision of G. Kearley.An extended-graphics option is included to enable rapidmanipulation of 3D images. Some of the group's softwarehas already been "unixed" and work is in hand to providemore powerful visualization facilities for users. In the firststage this workstation will form the main-stay of the groupcomputing activities but will eventually be supplementedby other workstations providing similar service at theinstruments.

Dr. D.S. Sivia from ISIS spent two weeks at the ILL toimplement his programs for Bayesian analysis of inelasticand quasielastic TOP data. The necessary modificationswere made to allow their operation under UNIX.

One instrument of the Group is being offered as aCRG-A operation: IN 13, the backscattering spectrometer onthe thermal guide H24.

IN4C New TOP spectrometer with Brillouin optionon the thermal tube H12

Preparation of the site for receiving the new spectrometerhas started, and premstallation of the shielding elements isforeseen in January 1994. The definitive installation of theprimary casemate will await the end of the reactorremounting. The Fermi-chopper and the two backgroundchoppers are to be delivered in the first half of 1994.The assembly of the double curvature monochromator withfour faces is in progress in Italy (Istituto di Struttura dellaMateria, CNR, coordinator Prof. F. Sacchetti, Perugia).A central forward scattering detector will be constructedby the Italian partner according to a design by the ILLdetector group.

Detector tubes for higher angles have been purchasedby the Italian partner who is also in charge of the detectorelectronics. The control and acquisition electronics havebeen conceived by the ILL electronics group and the majorpart has been ordered.

Since the reorganization of the Institute the project hasbeen attached to the new Projects and Techniques Division(see there for more information).

INS Multichopper TOP spectrometeron the cold guide H16

The chopper-suspension system has been damaged bya number of incidents since its installation 7 years ago.This system is a prototype. Results of running/repairsare generally unpredictable. So we have taken the opportunityof the long shutdown to address some of these problems.

The axles for the magnetic suspension were installedover the top of the original axles causing a rather flexibleaxis and serious assembly/disassembly problems. We havedeveloped new stiffer axles which if successful will be fittedto other choppers as failure occurs. We have also improvedassembly techniques within the bearing components sinceseveral failures were associated with parts becomingdetached during normal operation.

The performance of the adsorbing Gd2O3/epoxy coatingaround the periphery of the IN5 chopper disks has beenremarkable, since at other institutes smaller disks rotating atconsiderably lower speeds have experienced several failuresof this coating. This is all the more remarkable since therewas an error in the original calculations made more than25 years ago and recent finite-element calculations show thatthe coating should fail at the actual operating chopper speedof 20,000 rpm. The greatest stress is on the inner edge ofthe Gd2O-;/epoxy band and two choppers have had slightdamage at this point for some time.

These disks should be repaired to eliminate backgroundproblems, but in addition, the background could be furtherreduced by coating bo'h sides of all disks and filling in oneof the two windows on each disk.

- D S - TlM E-OF-F LICH Т AND HlGH RESOLUTION GROUP

The calculated stress at the weak point is 19.6 N/mm2

at 20,000 rpm and the best adhesion for epoxy resins foundafter tests with various surface treatments is 17.9 N/mm".This is in agreement with the manufacturer's claims.One disk was repaired regardless, but duly failed under testat 20,000 rpm. Disks run at up to 60 С and differentialexpansion between the disk and the coating providesan addition mechanism of failure.

We are now embarking on a test of a sputtered Gd2O4coating on one disk in order to test the adhesion andmachinability of this coating and to assess the consequencesof any distortion of the disk.

IN6 Focussing TOP spectrometer for long wavelengthson the cold guide HIS

The main improvement carried out has been the VMEchopper control and a new data acquisition program.The mechanical operation of the triple monochromator hasbeen tested before putting it back in place. The instrumentshould be fully operational at the beginning of 1994 andthe testing of the detection and acquisition system will becarried out by using a neutron source. Several safety featureshave been added to eliminate all possible risks of humanexposure to the neutron beam.

IN 10 Backscattering spectrometeron the cold guide H15

The programme of modernization of the electronicsis nearly completed. The new motors and coders can bedirectly controlled by the VME crate, thus permitting theremoval of the CAMAC controller. This upgrading wasnecessary in order to be compatible with the new type ofoperation, with a temperature scan of the monochromator,called INI OB. The high temperature cryofurnace usedfor INI OB is being assembled and tests will be done earlyin 1994.

A new device permitting a fast exchange betweenthe doppler drive (INIOA) and the cryofurnace (INIOB)has been put in place and is working satisfactorily. This hasnecessitated some changes in the heavy concrete housing.

During the first tests of INI OB it was noted that someelectric noise was produced by the start-up of the motorswhich are driving the motion of the lead curtain.This problem has been fixed by using electronic static relays.

IN 11 Spin-Echo spectrometer on the cold guide H141

The NSE spectrometer received its new coils which havea more precise winding and current connectors placed closetogether to minimize the magnetic perturbation of the cables.The marble was extended to allow an easy exchange ofthe secondary spectrometer for INI 1C, the high anglemultidetector extension. The cabling is being reorganisedfor the same purpose. The last big items for INI 1C (detectorprotection, analyzer support) arrived in December 1993.

The He flight box and the equivalent of the "Fresnel" coilsshould come in 1994. The main and analyzer magnets arealready mounted on the supporting mechanics and can nowbe easily attached to the sample table axis. If the watercooling is installed and if we have enough supermirrorsby the restart of the reactor, in principle neutron tests could bestarted. The electronics part is being slightly modifiedto handle the new configuration.

IN15 High Resolution Spin-echo Spectrometerfor long wavelengths on the cold guide H511(cooperation ILL-KFA-HMI)

New sample cells with quartz windows for small anglescattering in a temperature range of - 100° С to 300° С havebeen designed and realized.

The multidetector has been renewed: the entrancewindow deformation has been reduced from 7 to 3 mm,the gas has been changed and the rear cover has been sealed.

It has been decided to replace the 16.5 m longprepolarizing H511 neutron guide (FeCo coating on anantireflecting layer). About 9 m of the new guide will becoated with natural Ni while only 7.5 m will be coated withthe FeCo magnetic layer.

For the focussing option, new flat samples were tested.First, samples similar to the first prototype: it is thesubstrate, zerodur glass, which is polished to a ц-roughnessguaranteed less than 3 A (rrns) on the top of which a thinlayer (= 800 A) is evaporated or sputtered; Cu 6 5 ,Cu 6 5 + AI (120 A on the top of Cu), Ni,. xMo x and Сcoatings have been tested. A second type of mirror was alsoinvestigated: it is the Ni-"Kanigen" thick layer (on analuminium substrate) which is polished to the same(J.-roughness: = 3 A rms. The diffuse scattering atthe reflected beam has been measured on the neutronreflectometer at BENSC-Berlin. A signal/noise ratioof larger than 104 has been observed for all these samplesat Q > 0.0015 A"'. This was the sensitivity of the test in viewof a 5.IO"4 background level. The addition of a protectivelayer, Al-layer, does not produce any extra scattering.Surprisingly, the same quality is also achieved withthe Ni-"Kanigen" coating.

For the time of flight option, the permanent installationof the 3 choppers in the vacuum container and the completecabling of the safety devices have been carried out.The safety unit for the choppers, also for the velocityselector, has been connected and tested. The group of4 rotors can be driven and controlled locally froma Macintosh. The software for the remote control is stillunder development: ILL and ZEL-KFA-Jiilich collaboration.The vertical Jink between the master crate of INJ5 andthe crate for the TOF-unit is still to be solved.

- D S - Т I M E-O F - F LI G HT AND HlGH RESOLUTION GROUP

el" coilsnets arean nowe watermirrorsould be

odified

IN16 New backscattering spectrometeron the cold guide H53

Highest energy resolution in backscattering of better thanI цеУ is not available presently anywhere in the world. Sohow should it be tested whether the IN 16 monochromatorsand analyzers produce the desired energy resolution of about0.2 fjeV? A more tedious way than using a backscatteringspectrometer was to modify a small angle instrument toa backscattering spectrometer (especially tedious to explainthe long measuring times to SANS physicists). This is whathas been attempted again in another improved setup on the8m-SANS at the NIST. Gaithersburg (Frick, Gehring,Neumann).

The experimental setup is shown in Fig. 1. A goodcollimation was used for passing with a roughlymonochromatic beam (from deflection by a graphite (002)crystal) through a perfect, flat Si(l 11) crystal (0 = 2 cm)mounted on a MoBbauer drive which was calibrated andoptimized to achieve low vibrational amplitudes withan interferometer. The flat transmission crystal cutsan extremely narrow gap into the wavelength band of theincoming neutrons. Neutrons with wavelengths within thegap are then missing for the backreflection on the test object,the analyzer crystal. If the transmission crystal is movedthen this gap is Doppler shifted. Thus one can scan thewavelength band of those neutrons which are backreflectedfrom the analyzer to a detector of 50% efficiency. Of coursethis works only after a precise alignment.

Several crystals were tested: I) a perfect, flat Si(l ! 1 )single crystal, giving 0.1 8 ± 0.01 ueV, probably theresolution of our setup: 2) a spherical analyzer carrying flat,polished Si(l 11) hexagons, glued according to the "classic"INK) technique, giving 0.39 ± 0.034 цеУ and 3) a sphericalanalyzer of IN 16. carrying smaller ( 4 x 4 mrrr) polishedSi(l 1 1) crystals, glued with a new technique, giving0.38 +- 0.026 ueV. Thus about the same energy resolutionwas measured for 2) and 3). For geometrical reasons onewould expect a better resolution for the smaller IN 16crystals. However, the beam size might be the limiting factorand for intensity reasons it was impossible to reduce itfurther. Thus it is still an open question whether thedeformation of the crystals prevents obtaining a betterenergy resolution.

Furthermore a whole set of purposely deformed crystalsfixed with different glues was tested. The sphericaldeformation, i.e. the Sd/d which is enlarged by deformation,should be tailored to get the desired instrumental resolution:about I |4eV for the second analyzer set of IN 16 and about0.7 [leV for the NIST backscuttering project. Clearly higherreflectivity and a wider linewidth were measured (0.6 (JeV inthe case of a polished deformed 0.7 mm thick Si(l 11)wafer). Further tests of the analyzer crystals and thetechnique to fix them onto the backing plates have beenstarted at the Siloe reactor (Blanc, Frick, Magerl) and arevery promising. A Bonse Hardt camera setup is used and it

0 diaphragm,400 mrn ,18mm

choppergraphite(002)

^ selector

diaphragm36 x 36 mm monitor

moBbauer-driveflatSi(lll) 1900 mimonochromator 0 22 mm

sphericalSi (111)analyser

Fig. I : Experimental setup used at NIST to test IN 16 analyzers.

appears that with the higher flux available at Saclay,it should be possible to learn about the deformation usingbeam sizes down to 4 x 4 mm2. This enables us to measureonly one of the small single crystals on the analyzer plate.Such measurements are scheduled.

On the instrument itself several measures wereundertaken to comply with the health physics regulationsand to improve the background. The control programs andthe electronics are currently being reviewed by theelectronics and instrument computing group.

D7 Diffuse scattering instrument with polarizationanalysis on cold guide H15

D7 is waiting for neutrons. In the last year some moneywas spent on improving the safety of the instrumentaccording to the new regulations. The shielding can now beclosed by clamps on the front and rear. Also the doors atthe entrance of the beam tube must now be closed to enablethe shutter to be opened. In previous years it was easy toforget to close these doors, resulting in a higher background.The chopper has been equipped with a new drive and controlunit and the polarizer within the shielding has been equippedwith a step motor driven rotation table. This allowsadjustment to be made from outside, thus satisfying safetyregulations. We are now working with the new sputteringmachine to get an improved polarizer, which has a highertransmission for the shorter wavelength of 0.31 nm. In thisway we hope in the future to gain a fac.or of up to tenin intensity for this wavelength range.

Albert-José Dianoux

-DS- SMALL PROJECTS

GAMS5 Project :Two-axis bent crystal spectrometer

Hans Borner

The promising progress which has been made in recentyears in developing very high performance crystal bendingdevices has prompted the idea of using the ILL's reactorshutdown to build a new crystal spectrometer that willcombine the outstanding resolving power which can beobtained with the GAMS4 flat crystal spectrometer, and theoutstanding dynamic range obtained with the DuMondGAMS 1,2/3 spectrometers.

Analogous to the two-axis flat crystal spectrometer,successive Bragg reflections on two crystals situated behindeach other (with respect to the beam axis) eliminates directimaging of the source geometry which will then be no longercritical in further improving the resolution.

The principle of operation of this new spectrometer maybe inferred from Fig. 1. If y-rays of a given wavelength A. aresuccessively Bragg-reflected by the two crystals, the secondcrystal sees the y-rays as if they originated from the virtualimage produced by the first crystal. In this way thecharacteristics of the crystals (diffraction width 9r, bendingwith 0C) determine which portion of y-rays emerging fromthe target is twice Bragg-reflected. And, as can be derivedalso from Fig. 1, the target width 0S is no longer critical.

The basic layout of the GAMS5 spectrometer is verymuch an analogue of the GAMS4 two-axis flat crystalset-up. Likewise, it is equipped with high precision angleinterferometers. The distance between the two crystals is70 cm. The crystal bending devices allow us to vary theradius of curvature. All relevant interferometer parts whichsupport the optics are made from glass ceramics, exploitingthe extremely low thermal expansion coefficient of thesematerials.

The first version of this spectrometer will be equippedwith the GAMS5T interferometer which has been built inthe frame of a Miinchen -ILL collaboration and is currentlybeing tested.

image 2

rowland 2 image 1

target

Fig. 1 : Schematic diagram describing the principleof operation of the two- axis bent crystal spectrometer.The Bragg angle ф shown here is highly exaggerated.In realistic measurements ф is typically in the orderof several minutes to degrees.

The PIAFE Project (Production, Ionisationet Accélération de Faisceaux Exotiques)Study on PN1

Herbert Faust

The PIAFE project was discussed by the Institut desSciences Nucléaires (ISN) Grenoble and ILL scientists aboutthree years ago. A collaboration has been established aroundISN with several European countries which presently isworking on a study. The aim is to use a thermal fissionsource implanted in the PN1 beamtube of the ILL reactor toprovide neutron rich isotopes for transport via a beamline tothe SARA accelerator complex at the ISN, which is some400 m from the reactor. After delivery, the isotopes will beaccelerated to energies which are sufficient to surmount theCoulomb barrier so that they can enter into nuclearreactions. For this project the LOHENGRIN facility wouldhave to be modified. In addition, this would offer thepossibility of studying very neutron rich exotic isotopes at abeam port in the ILL reactor hall. A feasibility study showsthat with a neutron flux of 1014 n/cnrs in an internal sourcearrangement, fission rates of 2.2 I0l4/s can be expected in

-DS- SMALL PROJECTS

a 6.3 kW source containing about 2g of enriched " " U .The principles on the implantation of the thermal ion sourcehave been defined in an internal report (1). Ionisationschemes, extraction and considerations on the isolator havebeen addressed in this report too. Furthermore, theradioactivity has been calculated. In follow-up work thebeam optical system has been designed, including a periodicsystem of electrostatic einzellenses to confine the radioactivebeam to the axis of the beam-tube, and a first mass separatorwith a deflection radius of 55°. Also the use of the BILLmagnet as a high resolution mass spectrometer with А/ДА>5000 has been discussed (Fig. 1). Scientific aspects areaddressed in a report, which also reviews the possibilitiesprovided by a 30 keV exotic beam port at the ILL site (2).

References

( 1 ) H.R. Faust et al., internal report ILL 93FA9T.(2) Piafe Project Physics case, H. Nifenecker editor,

submitted for publication, Annales de Physique.

ч extractionfuel element

, periodicalelectrostatic Einzellenssystemmirror

'55° massanalysing magnet

deflectornigh resolution

ч magnet (BILL)ILL reactor hall H9-area

Fig. I: Implantation study of the PIAFE project in the H9 areaof the reactor hall. The beam is guided from the source near to thefuel element by electrostatic lenses to a mirror, a mass separatora/id the high resolution magnet BILL, which will be used as a massspectrometer. For purpose of acceleration, the particles can betransported to the ISN.

The He Polariser ProjectFrancis Tasset

1993 has been another year of intense competitionbetween the two possible routes (Hyperfine coupling of 3Hewith optically pumped Rb/Direct pumping on metastable3He atoms followed by compression) toward the productionof high density spin polarised gas. Although applications infundamental physics (SLAC and MAMI) have up to nowprovided the strongest motivations and tend to concentratethe high level of expertise and funding required, severalneutron scattering groups (Los Alamos, KEK, NIST, HMI)have begun significant investments into it.

At ILL, we have been following this development forseveral years. We started with a neutron test made on D3before the reactor shutdown, on a Rb pumped cell incollaboration with the group of Professor T. Chupp. Despitethe subsequent serious reduction in the scientific staff andthe instrument development budget, the 3He projectremained funded at a reasonable level and we could continueto work on it.

At the beginning of 1993, an experiment was done byW. Heil et al. at MAMI, the Mainz Microtron, usingpolarised electrons scattered on a dense polarised 3He target.A Toepler compressor was used successfully showing thatthe compression technique was possible, competitive andmuch cheaper than the Rb one being used at SLAC. Usingfunds from the European Community HCM programme

allotted to this development, I was able to spend 3 monthsin Professor Otten's laboratory and work with R. Surkau andW. Heil on the new 2-stage amagnettc compressor madeof large titanium pistons. The stay was very interestingand quite successful, culminating in a target being filled at3 bars and 25 % polarisation.

A detailed estimate for a duplication of this glass-metalmachine having shown that it is within the initial previsionfor this project, I reported on the project at the ILL ScientificCouncil held in October with emphasis on the Mainztechnique.

A further decisive step in this direction has beenthe arrival to Mainz, on 1 October, with the help of the HCMNetwork, of H. Humbot, a research associate, who gainedexperience in the field at Orsay in collaboration withM. Leduc at ENS. His first task is to build an optimizedsystem for Neutron Spin Filters in Mainz. This system is theproperty of ILL and will be transported to Grenoble as soonas it becomes operational/useful for our polarised neutronprogramme here.

Owing to this favourable arrangement, things are nowmoving fast. Most of the optical parts, including the infraredLNA laser, were ordered in a few weeks and were deliveredin 1993. We are now consulting prospective suppliers forthe mechanical parts.

In the meantime, decisive progress has been made inthe relaxation time in the high pressure cell. Being in Mainzjust before Christmas, I was delighted to see the following:

-DS- SMALL PROJECTS

a 150 cm~ cell was filled with 2 bars of polarised gas in37 min. and then closed. The polarisation was subsequentlymonitored every two hours by NMR. Two days laterChristmas was coming and I had to leave: the signal was stillstrong showing a relaxation time of 43 hours!

It is true that hard work remains to be done in perfectingthe second stage of the compressor in order to reach the highlevel of 3He polarisation which we know is necessary toproduce really intense polarised neutron beams. This is whyit is very important that we clearly show our interest andneeds to the people who are very skilled at it and probablyable to reach such high polarisations.

On the other hand, in a relatively short time, decisivequestions have been addressed with much success on severalaspects of this system. In a very pleasant venture withatomic and fundamental physicists, the compact,transportable, neutron spin filter is becoming a reality forneutron scattering centres.

Laue-detectorsMogens Lehmann

One of the instruments in the proposed modernizationprogramme for the ILL was a diffractometer for the study oflarge unit cells. It was based on the use of the quasi-Lauemethod with cold neutrons and a limited wavelength range.

Although no modernization programme has started,the proposal has spurred a number of tests of new detectortypes. The reason for this is simple. No neutron diffractioninstrument for macromolecular crystallography is of muchuse without a large position sensitive detector, andconsidering the eventual location of the instrument atan end-guide new types of detectors have been examined.These are combinations of neutron to light/y-ray convertersplaced in front of suitable detectors.

Two approaches have been studied. In one case thedetector was a position sensitive photomultiplier while inthe other case image plate technology has been used.

For the photomultiplier (Hamamatsu R2487) a 1.5 mmthick Li glass scintillator was placed in front of the 4.5 by5.5 cm2 detector area. The 17x18 anode signals wereconverted into two pulses for each axis using a resistorchain. These four voltages were then recorded into a PCusing a fast ADC converter and the position was calculated.

The detector was tested at the DN4 of the Siloë reactorin collaboration with staff from the EMBL and the CENG.It showed the method to be feasible. Counting rates of up to10 kcounts/sec could be handled and the overall countingefficiency was 30 %.

The main difficulty seems at present to be thebackground. This is undoubtedly due to a mixture of fastneutrons and y-rays, and more work is now underwayto handle the discrimination against the latter.

Another more ambitious project is the construction of animage plate for neutrons, presently being undertaken at theEMBL outstation in Grenoble with support from the FreieUniversitat, Berlin.

Image plates are well-known to X-ray diffractionists.They are normally made from flexible plastic sheetscontaining BaFBr doped with Eu~+ ions. When irradiatedwith X-rays, electrons can be trapped in isolated, metastablestates just below the conduction band. These states can bereleased by photo stimulation with visible radiation with theresultant emitted light lying in the blue region. The plate canthus be 'read' by scanning the plate with a laser whilemeasuring the intensity and position of the emitted light.After cleaning with an intense light source the plate can bere-used.

Image plates for neutrons are obtained by adding Gd tothe system, either as a thin plate in front or as a componentof the plate. The high (n,y) capture cross section for Gdensures a good detection efficiency.

The prototype detector is a 40 cm long, 30 cm widealuminium cylinder with the axis in the horizontal plane.The sample is placed in the middle of the cylinder, the beamis orthogonal to the axis and enters the detector through asmall hole on one side. The diffracted neutrons pass throughthe aluminium to be detected by the image plate which isplaced at the outside of the cylinder. After exposure this isread off much like one reads a phonograph. The pixel size is0.25 by 0.25 mm2, and the approximately 6 Mega pixels canbe read in 5 min.

At present the detector has been assembled, and firsttests are being done using X-rays. By the time of the reactorstart-up it should be ready for testing with neutrons. Againan important part of the test will be to estimate thebackground sensitivity. To minimize this the detector testsshould preferably be made at a location far from the reactorsurface, and preliminary measurements are therefore plannedto take place at the HI42 position about 110m from core.This is a cold beam with highest flux in the range from 3 to6 A, thus well-suited for the first Laue measurement tests.These can be done with the whole spectrum, while thedetailed characterization is undoubtedly best done witha narrower wavelength range.

- PROJECTS -

AND TECHNIQUES

DIVISION

(DPT)The Projects and Techniques Division (DPT - Division

Projets et Techniques) came into being on I July 1993.The purpose of the Division is to provide engineeringservices and project management support for all aspects ofthe experimental activities, including the computinginfrastructure. It is responsible for improvements andinnovation in the areas of beam distribution, neutron opticsand detectors, sample environment and data acquisition.The Division was formed from the three previously existingTechnical Departments - the Instrument OperationDepartment (EDEX), the Instruments and MethodsDepartment (DIM) and the Computing Department (DI).Some of the activities of these Departments were moved tothe Science Division (DS) and to the AdministrationDivision (DA). From EDEX, the instrument technicianswere transferred to the Instrument Groups in Science, andresponsibility for the Chemistry and Biology Laboratoriesalso passed to the Science Division; the Site and BuildingMaintenance Service moved to Administration. While theDIM remained within DPT, parts of the ComputingDepartment dealing with administration and officecomputing, as well as Telecommunications, passedto Administration, while some staff members of theDepartment formed the nucleus of a new ScientificComputing Group in the Science Division.

The remaining parts of these Departments have beenreorganized into two Branches: 'Instrumentation' and'Development', and a Project Office. The Project Office actsalso for the Sc'ence Division and helps to coordinate theactivities of the two Divisions. It is the intention that, in thefuture, major instrument projects are managed from withinthe DPT in order to better coordinate the limited resourceswhich will be available. Where necessary the scientistresponsible will be detached to DPT from DS to act asproject manager. Initially this arrangement coversdevelopments of the neutron guide systems, the new lime-of-flight spectrometer IN4C and the 'banana' detectorof D20. Other existing instrument projects remainthe responsibility of DS.

Although the DPT came into existence only in themiddle of the year, it is appropriate that the Annual Report ispresented in the new format of the new structure.Nevertheless it should be recorded that the old departmentalstructure survived until 30 June 1993. albeit with staffwidely dispersed, both in helping the reactor refurbishmentand on detachment to other organizations where theirtechnical skills could be used in the absence of experimentalactivity at ILL. Some found the 'grass is greener on the otherside of the fence' and will not return. We wish thema successful future.

The timing of the reorganization coincided with the firstdepartures under the FNE Convention (see Director'sReport). These included two of the Department Heads:J-C. Faudou and D. Rimmer. under whose leadershipthe DIM and the DI respectively had contributed so greatlyto ILL's reputation in technical innovation and in serviceto the users. We are particularly grateful to both of them forworking hard to the last minute to ensure a smooth transitionto the new structure. A. Heidemann, previously Headof EDEX, now heads the Instrumentation Branch andC. Zeyen has taken charge of the Development Branch.

Despite the perturbations of 1993. progress has beenachieved both in preparation for the reinstallationof instruments and in the various areas of technicaldevelopment. This work, of course, all started under the oldorganization.

In this, my first and last contribution to the AnnualReport as Head of Projects and Techniques Division, I wishto pay tribute to the skills, experience and dedication of allthe staff, which I am sure will carry them well into the newlife of the ILL after the reactor restart.

Peter Schofield

PROJECTS AND TECHNIQUES DIVISION

Project Office (W. Kaiser)

The purpose of the office in the new organization is toprovide information, assistance and advice to all thoseconcerned with the management of projects in the Scienceand the Projects and Techniques Divisions, on the allocationand control of the resources, personnel, facilities and financeof the various projects. The main activity was the updateof the financial situation of spending for the instrumentsin 1993 and the preparation of the budget proposalsfor investment on the instruments in 1994 and 1995.

Neutron Guides (W. Kaiser)H1-H2 Neutron Guides

As pan of the refurbishment programme, 139 m of thein-pile guides, in the swimming pool and in the casemate,are being replaced. In addition, the opportunity is beingtaken to carry out work in these areas to enable furtherimprovements of the neutron guides at a future date withminimum disruption to the scientific programme:

• The in-pile part of two new cold guides NG12andNG13.

• The replacement of 11 m of H25 by a supermirror guide.

The guides of the in-pile part of the H1-H2refurbishment have been delivered and the H2 guides aremounted in the mechanical support. The decision for thenew guides NG12-NG13 was taken in April 1993. The newin-pile mechanical parts, allowing seven guides for coldneutrons, have been delivered and will be equipped with theguides before the end of the year (see Fig.l, page 142).The supermirror guide for H25 is being manufactured.

The replacement of the electrical control for the vacuumsystem of the H1-H2 guides has been finished.

H17-H18 Guides

The decision was taken to modify the geometry of theseguides for a radius of 27,000 m to allow the installationof the diffractometer D16 on a new H17 guide and thesmall-angle spectrometer D17 on a new HIS guide.Therefore the H17 guide will not be refurbished in the out-of-pile part, and the HIS guide will not be available forthe reactor restart. Major modification of the casemate ofthe H1-H2 guides is necessary. Preliminary studies arein progress.

H511 Neutron Guide

The present polarizing guide for the neutron spin-echospectrometer IN 15 has been coated with FeCo at HMIBerlin. After the decision to replace 16.5 m of this guide,a call for tender was prepared and the order will go out.7.5 m of this guide will be coated again with FeCo at HMI.

IN4C Thermal Time-of-FIight Project(H. Mutka)

In the new organization of the Institut, the IN4Cinstrument project was attached to the Projects andTechniques Division. This reflects the main charge onthe work, as roughly 4/5 of the manpower associated withthe project belongs to this sector.

At ILL the main progress has concentrated on thechoppers. For a while a rather uncertain situation prevailedconcerning the availability of magnetic bearings for the newbackground chopper. Finally the initial idea of employingthe old choppers adapted for a vertical rotation axis, withone new background chopper, was abandoned. A set of threenew choppers was finally ordered and it is certain that thischoice will be an advantage in the long term. The Fermichopper and the two background choppers are to bedelivered in the first half of 1994. The Italian partner(Istituto di Struttura délia Materia, CNR-Frascati,coordinator Prof. F. Sacchetti) has concentrated on themechanical design and fabrication of the curvedmonochromator assembly. A successful working prototypeof a single row of eleven orientable elements has beenproduced. The full design of the four-face assembly withfive of these rows on every face has been terminated andfabrication will be completed before the end of 1993

Fig. 2: IN4C thermal TOP spectrometer: a perspective viewof the four-face monochromolor exchanger wider constructionin Italy. Each face has 5x11 orientable elements for obtainingthe double curvature.

PROJECTS AND TECHNIQUES DIVISION

(see Fig. 2). The graphite crystals for the monoehromatorhave already been purchased and the Cu crystals arein production at the ILL. The assembly will be availablefor tests in the first half of 1994.

The Italian partner has received detector tubes which arebeing lested. Work has also started on the detectorelectronics according to the layout produced in the ILLDetector Laboratory. The cooperation on the central forwardscattering detector is progressing, with some delay due to theunforeseen departure of the Head of the Drawing Office,who was in charge of the mechanical optimization. Thisdetector will be constructed by the Italian partner accordinglo a design established by the detector group of the ILL.

Preparation of the site for the installation of the newspectrometer has started, and pre-instullation of the shieldingelements is planned to start in January 1994. Definitiveinstallation of the primary casemate will wait until the endof the reactor remounting.

The remaining design work consists of the details of thesecondary flight box and sample environment, for whichthe concept already exists.

D20 High Flux Multidetectoron the Thermal Beam Hll (P. Convert)

The construction of the powder diffractometer D20 hasbeen dominated for many years by the realization of itsfundamental part, the large linear Position SensitiveDetector, or Banana, covering 160° with 1600 cells(see Fig. 3 on page 142).

At the end of 1992. we were faced with the departureof our expert technician. M. Berneron, who had made mostof the developments for the banana construction and hadessential skills for the realization of some critical parts of thedetector. Fortunately we were able to arrange his returnto ILL in October.

1993 was used to carefully prepare the mountingof the detector:

• Realization of several frames or supports forthe centring of the electrodes on their mechanical support,and their precise positioning on the mechanics of the detector:

• Construction of guard electrodes to improve theelectrical field homogeneity at the ends of the detector /.one:

• Cleaning of the cabin built for the dust-free assemblyof the detector;

• Production of the 96-cell D20 prototype reproducingexactly the conditions of the large banana; the complete setof guard electrodes: gas filling of 3 bars 3He + I barCF4:3 modules of 32 amplifiers; 3 units of 32 logics; 3 VME dataacquisition modules.

The 96-cell D20 prototype was successfully testedin March at LLB. The electrodes were found to operateperfectly: the electrode junctions have to be adjusted witha precision of 50 microns, the guard electrodes work well:the dedicated electronics are also working properly.

Following this, and after seven months of operation inthe laboratory with a neutron source, another test was madein October-November at the Siloé reactor (CEN-G).This revealed an instability in the gas amplification of theelectrodes. This question has now to be fully understoodbefore the mounting of the large detector can take place.This will be completed as soon as the problem has beenresolved.

All the pieces for the dedicated electronics are available(50 modules of 32 amplifiers. 50 units of 32 logics, powersupplies). The}' will be assembled at the beginning of 1994.

The data acquisition system is complete, tested andoperational, except for the synchronization module whichhas been designed but still has to be made.

1994 will be very busy in order to completethe instrument by the end of the year:

• Solving the problem of instability of the electrodeamplification:

• Mounting of the banana:

• Assembly and test of the dedicated electronics:

• Mechanical modifications of the old diffractometerplatform to receive the banana;

• Reinstallation of the HI 1 primary shielding:

• Shielding of the experimental area:

• Instrument control in VME standard(motors, encoders);

• Software for the D20 control with the Silicon Graphicsdedicated computer;

• Production of the mechanical support for the HOPGmonochromator. and adjustment of the 52 blades.

-DPT- INSTRUMENTATION BRANCH

Instrumentation Branch

(A. Heidemann)

IntroductionAs part of the new organization of the ILL the

Instrumentation Branch was set up in the Projects andTechniques Division. This branch covers all activitiesconcerning the construction and maintenance of the ILLinstruments. It is responsible for the construction andinstallation of the instruments, for the delivery of neutronsto the instruments, for the design office and mechanicalworkshops (Central Workshop. Hall d'Essai), for instrumentcontrol and data acquisition, and for the computinginfrastructure excluding Management Information Systems.The Instrumentation Branch consists of five Services:

• Neutron Distribution and Central Services.

• Mechanical Engineering.

• Electronics.

• Computing: Instruments and Network Infrastructure.

• Computing: Systems and Communications.In addition the Branch has responsibility for managing

two major projects: the refurbishment of the beam shuttersand the programme for the reinstallation of instruments.

The Services have the following responsibilities:

Neutron Distribution and Central Services

• Systems for the supply of neutrons to the instruments(neutron guides, beam shutters, beam stops, safety loops).

• Operation and maintenance of the experimental halls.

• Vacuum systems.

Mechanical Engineering Service

• Finite element calculations for the layout of instruments.

• Mechanical design of instruments by the DrawingOffice

• Preparation of new instruments by the 'Hall d'Essai'and the Central Workshop.

Electronics Service

• Design, construction, testing and maintenanceof instrument control and data acquisition systems.

Instruments and Network Infrastructure Service

• Instrument computers and softwarefor the four condensed matter instrument groups.

• Hardware of the scientific computing networks.

• Coordination of the networks on the site, .ncludingconnections to ESRF, EMBL and externally.

Systems and Communications Service

• Administration and operation of central computingfacilities and of workstations.

• Data base and archives.

• Software libraries.

• Electronic mail.

• Micro-computing (PCs, Macintoshes).

• Instrument control and computingfor the Nuclear & Fundamental Physics Group.

It is hoped that despite the considerable reductionin staff, of the order of 25 to 30 % during 1993 and 1994compared to the situation in 1991, we will still be ableto provide reasonable technical support to the instruments.In the following section we present the activities of theInstrumentation Branch during the year 1993 in more detail.

Neutron Distribution and Central Services(R. Mathieu)

The main activities have been as follows:

• Contribution to the project for modernizingthe beam shutters.

• Coordination of the work on the following instruments:EVA, PF1, GAMS5, and studies for the acquisitionof the possible CRG instrument ADAM.

• Safety studies for certain nuclear physics experiments:I V 7Luand l 9 8AuonPFl.

• Work on the experimental halls ILL? and 1LL22:cleaning, painting, removal of old cables, etc.

• Contribution to the scheduling of the reinstallationof instruments.

• Assistance to the construction teams on the reactor:lifting, internal and external transport.

• Intervention work on instruments and the reactor.

• Production of poster boards to illustrate the functionand purpose of the instruments, which will be installed nextto the instruments after the restart.

• Assembly of an 'historical' exhibition in the old libraryin ILL4.

• Coordination of sales of sample environment equipment.

Mechanical Engineering (M. Thomas)Although the ILL's scientific activity was reduced during

the long reactor shutdown, the mechanical engineeringgroup's workload has not diminished, owing to the work inprogress for the ILL instruments and its contribution to thereactor refurbishment programme.

Assembly Hall and Workshop

The assembly hall, with the assistance of the NeutronDistribution and Central Services, undertook the project forrebuilding the mechanical parts of the beam shutters and

safety loops. Some of the more usual activities of theassembly hall have continued, such as the assembly and testsof the IN 15 choppers, the D22 velocity selector and therebuild of the controls of the Dl 1 velocity selector.The workshop was able to assist with the reactorrefurbishment by responding very quickly to therequirements of the project.

Drawing Office

Summer 1993 saw a change of engineer in charge(departure of A. Bill ing ton end of July and arrival ofP. Malbert beginning of September) and a reduction of staffby early retirement and detachment. The main activity wasconcentrated on improvements for existing instruments andon new instruments.

Improvement of existing instruments

• GAMS2/3: completion of the rebuild.

• New secondary spectrometer for IN 11with a multidetector.

• Sample areas of the instruments Dl 1, D17 and D22.

• Continuation of the study for the installationof the new multidetector for the instrument D20.

• Monochromators for D2B, D19 and D20.

• Multidetector modification for DI9.

New instruments

• Gamma spectrometer GAMS5.

• Continuation of intensive studies for the TOPspectrometer IN4C.

• Study of the Brillouin spectrometer IID.

Preliminary projects

• Installation of instruments ADAM and PFIon the H53 neutron guide.

• Installation of the instrument IN22 (previously IN20B)on the H25 guide.

• Modification of the H17/H18 guide area in viewof the installation of the future reflectometer (rebuild of D17).

Calculation Laboratory

The most significant of the studies carried out were:

• Study of the static behaviour of the IN4C vacuum box.

• Stress and dynamics verification of the IN4CFermi chopper.

• Optimization of the housing of the IN4C multidetector.

• Characterization of elastic behaviour of flexure-basedrotation modules for the ultra-fine rotation stage of GAMS5.

• Non-linear contact analysis of elastic behaviourof the reactor flange clamping collars.

• Magnetostatic study of neutron precession coilswith superconducting Meissner screens.

• Mechanical analysis of the anticlastic curvature effectinduced by the bending of a thin rectangular plate.

• Study of the elastic behaviour of a bilayered materialsubjected to a transversal and time-dependent thermal gradient.

• Study of the IN5 chopper disks under the effectof rotation (see Fig. 4 on page 143).

Electronics (R. Klesse)The activity of the Electronics Service was concentrated

on the following topics:

Improvement of existing instruments

The three-axis spectrometers INI and IN8 are in theprocess of being equipped with VME electronics.The backscaîtering spectrometer IN 10 is now fully VMEcontrolled and has been recabled. Dll was changed fromCAMAC to VME within three months, and the electronicswere considerably reduced. T13C was mounted on a VMEplus Macintosh base and has become an independentmoveable device. The instrument was running satisfactorilyfor the whole of 1993 at Orphée (LLB).

Preparation of the new instruments

IN15. IN16 and D22 are ready for commissioning in1994. On D22 all motors are connected and running. Dataacquisition is done with a new VME-VSB histogrammingdevice which can handle more than 10 events per second.

Restart and tests of all the instrumentsin the two neutron guide halls

Many problems have been encountered causedby the two-year shutdown. Most of them have been solved.

Technical assistance to other ILL services and externallaboratories (HMI, ESRF, PSI, Thomson, etc.)

During the period of the reactor shutdown, staff havebeen detached to other institutions, and work has beencarried out under contracts.

Computing: Instruments and NetworkInfrastructure (A. Barthélémy)

The main aims of the Instruments and Networks Servicein 1993 were:

• To maintain the equipment correctly to facilitatethe restart of the instruments.

• To restart and test the neutron guide instrumentsand to continue software developments on new instruments.

• To modernize and to standardize the older computingequipment.

• To prepare the local network for decentralizationof computing.

• To maintain a high technological level.

Maintenance

The instrument computers have remained connected.In this way the number of breakdowns has been reduced,but some units have had to be changed.

Restart of the Instruments

All the computers of the instruments on the neutronguides are operational. With the replacement of certainelectronics systems, software developments have been carriedout. This change has made it possible to check the cabling.

Modernization of the Instrument Computers

The PDP11 computers have been or are being changed,except on D3, D7 and INII. For D20 a Silicon Graphicsworkstation has been purchased, and for the three-axismachines a DECstation 3000-300L and a Hytec CAMACcontroller have been delivered.

The acquisition and control programs for a large numberof instruments have been modernized and standardized onthe MAD program (IN5. IN6, INK), IN 16, DIB. IN3. IN 12,DIG, DB21, D16, Dl I. D17, D22).

Fig. 5 presents an overview of the types of computersand electronics systems installed on the ILL instrumentsat the end of 1993.

Changes in the Local Network

Considerable technical and financial efforts have beenmade on the ILL local network:

• An FDD1 ring has been installed as part of the UNIX plan.

• A fibre optic Gigaswitch concentrator is operational;its two main aims are to permit rapid access lo ILL serverswith a possible evolution towards asynchronous transfer mode(ATM), and to prepare for changes in the computing centre.

• The asynchronous cabling has been updated withelimination of unused cables, and the installation of newterminal biprotocol servers and the gradual eliminationof the line concentrators (MJCOM. PDPI1 ) are in progress.

• A computerixed system for updating the cabling plansis operational.

• Studies are in progress for a joint program of the ILL,ESRF and EMBL networks towards RENATER plannedfor 1994.

• Monitoring of the network has been improved by wayof the network management station and specific productson Macintoshes and PCs.

INSTRUMENT COMPUTERS

VAX stationGPX CAMAC

micro VAX IIVME

Silicon GraphicsVME

LOCAL TREATMENT STATIONSSilicon Graphics D2BD10VAX station 3100D11 D17D19VAX station GPX D7HP stations 9000 PN1 PN3

PFIPF2

DEVELOPMENT SYSTEMSMicro VAX IIPC Windows NTDEC station 300Q300LDEC station 5000-200POP 11/24VME OS9 systems

IOCAL NETWORKS SYSTEMSVAX station 3100PC SnifferMacintoshRouter CISCOVAX station 2000

_ externalnetworks

VAX stationGPX VME

PCs MS-DOSCAMAC

PCs MS-DOSGPIB

Fig. 5: Overview of the types ofmmputers find eleclronirs systems

initialled on the ILL instrument!! til the end i>/ /ЧЧЗ.

Technology Monitoring

The increasingly rapid development of computing makesit necessary to be extremely vigilant about future choices.A study of the possibilities of the Windows NT systemfor operation of the Microsoft instruments has been initiated.

The new technologies of the local networks have beenstudied in particular as the local, national and internationalnetwork has become fundamental in the context of moderndecentralized computing.

Computing: Systems and Communications(M. Le Sourne)

At the end of 1992 we submitted lo the SteeringCommittee at its request the broad outlines of a UNIX planproviding for the progressive conversion of our computingapplications to a UNIX environment. This plan was acceptedas a whole, and an initial budget was provided for 1993.A considerable part of our activities has therefore involvedthe implementation of the investment plan and theestablishment of a first platform to permit this work to start.The conversion to UNIX is a major operation, which willrequire lime and effort from scientific and technicalpersonnel, and it is clear that in the context of the reductionin staff this can only be implemented very gradually.For this reason we have also worked on the developmentof our central VAX system, so that for the immediate futurewe can maintain a VMS service appropriate to our needs

Fit;. (У : The stock <>j computing equipment available for scientific

applications at the end of 1993 shown schematically.

and our financial means. Fig. 6 shows schematicallythe stock of computing equipment available for scientificapplications at the end of 1993.

The first investments have been for the purchase ofworkstations. To this end a study was carried out to comparethe main equipment on the market; after considerable debatebetween ihe scientists and the computing staff, the choicewas made of Silicon Graphics (SGI) and Hewlett-Packard(HP). Five instrument groups have received UNIXequipment:

• 2 HP stations for the Theoreticians.

• 2 SGI stations for the Diffraction Group.

• 1 SGI station for the Large Scale Structures Group.

• 1 SGI station for the Time-of-Flight and HighResolution Group.

• 1 HP station for the Nuclear Physics Group.

Reconfiguration has been carried out of one Dec5000 station to act as server for X terminals and file server.

The graphics group initiated talks with the scientiststo define the broad lines for graphics support and conversionto UNIX. This resulted in time investment in marketstandards such as XI1, OSF/MOTIF, GKS, PHIGS,in evaluation of graphical packages such as KHOROS, AVS,etc., and in comparison of user interface builders (GUI's).In parallel we have introduced in this rather heterogeneousenvironment a few X terminals which were selected, afterevaluation, from the Tektronix range.

During the whole of this period the members of theService, with the aid of a number of training courses, haveacquired considerable experience in the managementof UNIX equipment and the organization of these systemsfor client/server. For day-to-day operation a procedure hasbeen introduced to provide backups for these systems.A study is in progress for the choice of a product for savingand archiving in a heterogeneous environment.

There are several reasons, both financial and technical,why UNIX cannot be introduced immediately in its entirety:

• The investment cost of UNIX-based systemshas to be spread over several years;

• The existing VAX instrument computerswill continue to work at the reactor restart;

• There is an enormous investment in users' datatreatment programs, written in older versions of VMS Fortran.

It was therefore found necessary to maintain a centralprocessing service operating under VMS for the time being,in parallel with the installation of the UNIX computingfacilities. The decision was accordingly taken to lease aDEC Alpha 3000 - 500 AXP computer which can run eitherVMS or UNIX environment. It will enable a smoothtransition to be made at the time when a VMS centralservice is no longer required.

Data Base and Archive

The database has been renewed for integration in theUNIX environment. At present the VAX central systemstores experimental data in binary format. In parallela UNIX base will store the same experimental data in textmode. This will be maintained on a UNIX server with a treestructure permitting easy access to information. Some of thetreatment tools, represented by a library of subroutines,have been made available to the users.

Software Libraries

One of the responsibilities of the Service is to providelibraries, compilers and development tools on the stationsand servers.

• The Nag Fortran library has been installed on a UNIXserver. With a view to ensuring continuity, we have set upthe Harwell library for different types of stations.

• For'ran 90: a new version of this compiler has beeninstalled and we have produced a document giving practicaladvice for the conversion of programs written in VAX Fortran.Fortran 90 compilers will be available from manufacturersduring 1994.

Communications and E-mail

The ILL IP network is an Internet domain named ill.fr.Primary and secondary name servers have been installed ontwo existing DEC - 5000 stations. A mailing gateway hasbeen defined, one of the functions of which is thedistr ibution of mail to UNIX stations and alsoto Macintoshes and PC's. The service has also providedconsiderable assistance to users to enable them to make fulluse of the possibilities of Internet. The extension of ourcommunications on this network has made it possibleto eliminate the EARN link with Montpellier and the linkwith the HEPNET network.

Micro-computers

The stock of micros at ILL may be estimated at the endof 1993 at about 100 PC's and twice that numberof Macintoshes. For all these Micro-computers, the Servicehas provided first level intervention work, which has madeit possible to reduce maintenance costs considerably.

Macintoshes, extensively used for word-processing, areincreasingly utilized in the scientific sector for variousfunctions such as the presentation of documents, emulationof graphic terminals and X terminals, data treatment,electronic mail on IP network and access to Internet servers.

As regards PC's, these are more oriented towardsspecific tasks related to management applications andtechnical applications, and for the control of Nuclear Physicsgroup instruments.

The aim has been to make these two environmentsas uniform as possible for the use of printers, exchangeof documents, and their integration in the worlds of UNIXand VMS.

Support for the Nuclear and Fundamental Physics Group

On the basis of the timetable and forecasts producedin 1992, the group is firmly oriented towards the use andintegration of PC's for control of the Nuclear Physicsinstruments PN1, PN3, PF1 and PF2.

The first few months were devoted to the overall studyof PC's in the DOS and Windows 3.1 systems, and in thechoice of software to be used both for experiment programsand for publishing and data treatment supports. The maindirection is the choice of Microsoft software which, withoutbeing the most powerful, resolves the problem ofcompatibility between software, which goes in the directionof efficiency and reliability. The group is currentlysupporting the following software: DOS 6.0, Windows 3.1,Word 2.0C, Excel 4.0, Visual Basic Pro 3.0, Access 1.0,

LAN Manager network and LABVIEW 3.0. For thecalculations we have adopted Fortran 90 from LAHEY,which provides good compatibility with the VAX.

With a view to confirming the consistency of these ideasand their applications, we contributed to a considerableextent to the implementation of an experiment at ESRF,in coliaboration with C. Vettier. This experiment operatesvery well in accordance with specifications: four codedmovements and one acquisition system: monitor, timer,detector with scans and graphs.

We also incorporated a CAMAC driver in Windows 3.1in order to connect the electronics which will not be changedin certain experiments (e.g. PF2). With the help of this driverwe have produced an acquisition program skeleton basedon object programming. In the context of the experimentswe also restarted the magnet of the spectrometer BILLin collaboration with K. Schreckenbach (Munchen).

Another aspect of our activities has been the renovationof the data acquisition system for the reactor (TCMS II),including design study, drafting of specifications, selectionand ordering of hardware and software.

The aims for the coming year are: the restart of PF2,planned for February 1994, then PN1 for March, PN3for August and finally PF1 in the last quarter of 1994.

Coordination of the Reinstallationof the Instruments (D.A. Wheeler)

The first objective, to have all the instruments in theguide halls operational by the end of 1993, is well in hand,although a few instruments will not achieve this dueto technical difficulties.

The second objective, to have all of the 25 scheduledinstruments operational in the middle of 1994, is dependenton the date of installation of the reactor block as work on thelevel С instruments cannot start until the reactor beam tubesare installed. The reinstaflation of the instruments, whichwill mobilize more than 60 persons from the ScienceDivision, the Administration Division and the Projectsand Techniques Division, should in large part be achievedby the middle of 1994 as planned.

Beam Shutter Modernization (W. Kaiser)The activity of the refurbishment of the beam-shutter

system under Quality Assurance was concentrated onthe H1-H2 neutron guides and the instruments in the ILL?guide hall, which concerned 52 out of a total of 72 shutters.The shutter mechanism, the electro-pneumatic and electricalcontrols including supply of compressed air are completed.The new interlock system with keys for gate and shuttercontrol is in place.

-DPT- DEVELOPMENT BRANCH

Development Branch(C.Zeyen)

With this year's reorganization of the ILL the followingactivities were combined under the common label'Development Branch': Monochromators, Detectors,Multilayers, Cryogenics, High Temperatures and Pressures.A new group 'Instrumental Techniques' was created, but itsactivities could not start because the entire staff had to helpout in other areas of the ILL. The projected activity of thisgroup (B. HAMELIN) will aim initially at a more efficientuse of the reduced number of instruments as well as ofthe reduced number of cycles. The Development Branchstaff had to show a great deal of flexibility this year sincein many instances laboratory and project activities had to bedone in parallel with help to other reactor or instrument-related activities.

Monochromator Laboratory (A. Magerl)Immediately after the present shutdown in 1991

the Monochromator Group transferred one of its neutrondiffractometers for crystal testing, T13C, to theneighbouring Siloé reactor. This proved extremely valuablefor ongoing work of the group, and the long list of otherusers underlines the need for general purpose instruments.Nevertheless, the moderate beam quality and the limitedavailability of the beam made it desirable to transfer thisyear the complete second test diffractometer Т1 ЗА to a beamposition at a cold neutron guide at the LLB reactor at Saclay.The instrument is now installed with a fixed take-off angleof 90° for the primary diffractometer, but differentmonochromators such as HOPG, and Si 111, Si 113, andSi 115 made from oxygen-precipitated Czochralski crystalsoffer a good choice of wavelengths and resolutions witha very good beam quality. Monochromator componentsmeasured so far include Si crystals for applicationsin backscattering, HOPG for D20, Be-project, Ge for D2B,and Cu for IN4C and for LLB.

The present strong request for diffraction techniquesother than neutrons puts a heavy demand on the group'sX-ray and y-ray diffractometers which have been heavilyused throughout the year. However, parts of these facilitieslike the electronics and some mechanical components showserious signs of wear. For the near future improvements/investments need to be envisaged if these experimentaltechniques are to be maintained, and alternative possibilities,as offered for example by the proximity of the ESRF, shouldbe considered as well.

A new hot press for plastic deformation has beenconstructed and built in collaboration with the ILL hightemperature laboratory. At present it is about to go intothe test phase. This device is mechanically much more stable

and precise than the old hot press, which has been in usefor about 25 years, but which now lacks completely themechanical precision and temperature homogeneity needed.

The work of the group was largely concentrated on themanufacture of monochromators for IN4C (Cu), D2B (Ge)and D20 (HOPG). These are three major and work-intensiveprojects. For example, the IN4C monochromator needs 110individual Cu crystals! A significant support was alsoprovided for IN 16. The particular question here is howto cover the large spherical surfaces of 7 nrr for themonochromator/analyser system with Si crystals whichshould either be stress free to achieve highest resolutionor which should have well-defined stress conditionsto obtain, say, a 5-10 times increased neutron flux.

In addition the group is occasionally asked for urgentassistance when installed monochromators fail. This yearthe IN3 graphite monochromator was broken when theinstrument was modified, and the Ge monochrornatorof Dl A was destroyed due to an imploding guide at LLB.

This year the Be-project came to a formal end.This project linked several major neutron scattering centres(PSI, Switzerland; HMI, Germany; BNL, USA, and TohokuUniversity, Japan) with the ILL and with the Max PlanckInstitut at Stuttgart in an attempt to grow Be crystals suitablefor a neutron monochromator. It turned out that this goalwas much more difficult to achieve than expected in thebeginning. Nevertheless, there has been steady progress overthe years concerning both the growth of high quality singlecrystals and the creation of an appropriate micro structure byplastic deformation. These studies have been continued bothat Stuttgart and at the ILL within the framework ofa diploma thesis. It has been possible to produce a suitablemosaicity for the required crystallographic plane with thecorrect anisotropy. Recent investigations with 1 mm-thickBe blades have shown that it is possible to approach forlarger areas the reflecting power of Cu crystals. Furtherprogress is expected from a continuation of the presentstudies in the form of a Ph. D. thesis project which is beingcarried out in collaboration with the TU Freiberg and theMPI Stuttgart.

Another research project in collaboration with the INPG,Grenoble, was continued successfully during this year.it concerns the synthesis of Si | . xGe x crystals by a lowpressure CVD technique. The aim is to replace the mosaicityof monochromator crystals usually employed by a gradientin the lattice spacing for increased beam intensity.The diffraction properties have been calculated recentlyby a transfer matrix technique, and typical results are shownin Fig. 7. It needs to be noted that full reflectivity over anextended wavelength range can be built up in both Braggand Laue diffraction geometry by a proper choice of thegradient of the lattice spacing. Some experimental results areshown in Figs. 8 and 9 (page 143). Fig. 8 shows a neutrondiffractogram taken at the high resolution time-of-flightdiffractometer of the TU Miinchen for a crystal with

deviation y from the Bragg-position

-10deviation y from the Bragg-position

Fig. 7: Calculated diffraction profiles ofSii..flex crystals,which have a width of the reflection profiles five times largerthan the Darwin widths of a perfect crystal, with optimizedgradients in Bragg and Lane geometry, respectively. The curvespresented are calculated for a crystal thickness often timesthe extinction length. The reflection profiles for perfect crystalsof infinite thickness are shown in a deeper colour.

six Si,.xGex layers with x = 0.08, 0.14, 0.19, 0.24, 0.29, and0.32. The main peak originates from the thick Si substrateand the six additional maxima stem from the depositedepitaxial layers. Their reduced intensity and increased widthis due to the fact that the thickness of the mixed layersof about 15 цт is only about half the extinction length.The peak position for x = 0.32 corresponds to a changeof the lattice parameter of Ad/d = 1.3 %! Fig. 9 (page 143)shows a two-dimensional intensity plot in a colour code andits one-dimensional projection into a longitudinal diffractionscan of a Si].xGex crystal where the concentration wasvaried continuously during crystal growth between0 < x < 0.03. Such high energy У-ray diffraction data weretaken at both HASYLAB at DESY, Germany, and NSLSat BNL, USA. Clearly the build-up of both mosaicity andgradient of the lattice spacing can be seen for this crystalwhereas usual monochromator crystals after plasticdeformation only show mosaicity.

s: o.o

10 20 30

Germanium concentration x [%]

Fig. 8: Neutron diffraction scan of a Si/ .лСс\ with x = 0(main peak from the Si substrate), midx = 0.08, 0.14. 0.19, 0.24.0.29, and 0.32 (data taken at the high resolution time-of-flighldiffractoineter at the FRM, Munich).

Finally it should be noted that a Workshop on 'FocussingBragg Optics' was organized jointly by the ILL and thePhysikalisch-Technische Bundesanstalt Braunschweigin May. From all the contributions it became clear that thereis still a large potential for improved neutron optics relatingto new focussing principles and techniques to makeoptimized use of neutron beams.

Detector Laboratory (A. Oed)The detector laboratory staff was reduced, in the course

of the reorganization, from six to four. It was therefore notpossible to continue with all the projects which werein progress. In particular, no further development of the newneutron microstrip gas detector technique could beundertaken. Nevertheless a large number of successfulmicrostrip proportional counter (MSPC) applicationsin a variety of fields were reported at the MSPC-workshop(Report ILL 93 GE 048) held at the ILL this year.

A position-sensitive two-dimensional MSPC detectorwith charge division which was described in last year'sreport was successfully tested at the PSI reactor. For themoment the data acquisition rate is limited by the PC-baseddata system to about 7 kHz. A modification of the software,which is being implemented, will however allow dataacquisition rates of up to 20 kHz.

The prototype of the D20 large MSPC was extensivelytested, together with its VME electronics, at the Saclayreactor last March. Very high data rates at a perfectlyconstant detection probability over the entire detectorsurface were recorded. Further tests during the rest of theyear were undertaken at the laboratory with a neutronsource. The latter tests revealed a modification of themicrostrip glass substrate, and hence of the detection signalamplitude, in the course of the last nine months. To avoidthis problem in the future, a thin electronically conductingglass coating is envisaged. Promising tests have alreadybeen undertaken by the glass manufacturer. The general

future solution to this problem will be the regular useof electronically conducmig glass substrates, insteadof the ionic-conduct )T glass used in the D20 detector.The two-dimensional MSPC mentioned above is alreadyequipped with electronically conducting glass substratesfor the microstrips.

The ILL cryogenic laboratory has designed and delivereda • He distillation and purification unit which operates verysatisfactorily (see Fig. 10 and Fig. 14 on page 144).

The detector group is also involved in the constructionand further development of multiwire detectors. Thefollowing detectors were renewed or repaired: the gas chargeof the IN 15 multidetector had been polluted and wasreplaced. The opportunity was taken to pre-stress the entrywindow using a double-electron-beam weld technique inorder to reduce its deformation. With the new filter gas( 1 bar 3He + 03 bar CF4 instead of 1 bar 3He + 0.5 bar C,HS)the window deformation is reduced from 7 to 3 mm.

The D15 multidelector has been reopened and two anodewires were found to be slack. All the anodes were rewired.After remounting and tests (D. FELTIN, Charactéristiquesdu multidétecteur de D15. DIM-93/022-DF) this detectorwas lent to HMI Berlin.

The Saclay mullideleclor was repaired at ILL (underguarantee). The 128 x 128 cell detector (1.5 mm spacing) hada deformed entry window and a cracked cathode glass plate.

Both this multidetector and the IN 15 one have passedsuccessful neutron tests and the detector casings are beingclosed by welding.

Multilayer Laboratory(I.S. Anderson, O. Schàrpf)

Both evaporators have been used continuouslythroughout the year for the production of Co/Ti polari/.ersand Ni/Ti supermirrors. In addition to meeting in-house

I 150008 10000

5000О0 200 400 600 800

pulse height1000 1200

Fig. Ill: Piil.w lieixln spectrum of the ''He detection mictionmeasured in the laboratory with tin Ant-Re neutron suture and 'fie,t,'(/.v recovered ami purified using the new cryogenic unit.

demands, polarizing benders were supplied to the NationalInstitute of Standards and Technology, Washington D.C. andthe Physikalisch Technische Bundesanstalt, Braunschweig.Supermirrors for a focussing device were also producedin collaboration with the Technical University. Munich.

Although it had been foreseen within the modernizationprogramme to purchase a new sputtering facility, hopesto improve the multilayer quality were dashed when themodernization programme was stopped. Fortunately the ILLhas signed a collaborative contract with the University ofEvry. permitting the installation at ILL of a 'state of the art'sputtering facility recently developed for X-ray multilayersat the Laboratoire d'Électronique Philips (LEP).

The facility (see Fig. 11 on page 144), consisting of aUHV chamber with four RF sputtering positions, load lockmodule, on-line kinetic ellipsometry, quadrupole gasanalysis and a multitude of ancillary equipment wasdismantled by W. Graf together with the LEP staffand delivered to ILL at the end of April. The installationand commissioning of the primary functions: vacuum, watercooling, RF power, ellipsometry, were carried out duringApril and the first films deposited at the beginning of June(see Fig. 12 on page 144). In addition to significantimprovements to the basic programs, notablysimulation/fitting of ellipsometry traces (see Fig. 13) andPC-based control of the quadrupole gas analyzers, a numberof technical modifications have been made to the facilityto enable the deposition over 30 cm-long substrates.

deposition of an iron film

0.1 0.2 0.3

Tan (\|/)

0.4 0.5

rig. /.?: On-line ellipsometry essentially determines the complexindex of refraction of a film hy evaluating the ellipsicity ofpolarised light after reflection. The variables 4/and Л characterizethe dielectric function of the deposited layer and its thickness.The figure shows the ellipsomelry trajectory during the depositionof an iron film onto glass. The deposition follows the directionof the arrow, each point corresponding to a step of about I.5Â.The first pan of the curve can he simulated hy an amorphous Fcfilm containing a 20'/i mid fraction. At a thickness offiOA a suddenstep in the trajectory can he seen, corresponding to spontaneouscrystallization of the film. After crystallization the trajectorycan he well simulated hy growth of a dense film with the refractiveinde\ of pure iron.

tional. and

weig.need

ationopes

of aJock

Presently (he hardware is being adapted lo cater for 20 cm-wide samples and the optimization of the uniformity shieldsis in progress.

Furthermore a series of ex-situ analysis techniques hasbeen set up to characterize deposited films includingmechanical profilometry, quartz thickness monitors,spectroscopic transmission and X-ray reflection. We are thusready to achieve our aim: the production of significantlyimproved supermirrors for the neutron optics of ILL.

Cryogenics (D. Brochier)Standard Cryogenics

The campaign for repair, modernization, and testsof standard ILL cryostats has been continued. The newmodel of sample holder, with a much shorter response time,is being generalized. Following previous development,a pneumatic cold valve has been perfected and isprogressKely installed on all standard cryostats. Theassembly and testing of a special liquid nitrogen cryofurnacehas been carried out. The Cryopad 2 (for neutronpolarization analysis) has been assembled, tested and putinto service (for the standard cryogenics part). Assistancehas been provided for the drawings of the precession coils.

Assistance has been provided to other groups, for example:

• Construction, assembly and testing of a halogen mirrorfurnace:

• Welding for the Reactor Division;

• Preparation of experimental devices for the ESRF;

• Temporary secondment of a technician forthe installation of the new beam shutters, and re-installationof fluids distribution on experimental areas;

• Assembly of an ultra vacuum bench for 3He cells(neutron polarization by polarized ^He project);

• Study, assembly, final testing of a cryogenic • Hepurifier for large quantities of -'He, see Fig. 14 (page 144).After some assistance for the commissioning, the DetectorGroup routinely operates the system.

Very Low Temperatures

The SERC dilution insert has been repaired and re-tested.

The bottom section (heat exchangers, 1 К pot, still)of the 5 mK dilution fridge has been recently deliveredby the CRTBT. It has been assembled with the thermometry.It is currently being tested.

The collaboration with A. Benoit (CRTBT) on thedevelopment of a new a-gravitational dilution techniquehas been continued, and has shown very interesting results:

• Bolometers for the TESTA GRIGIA telescope havebeen characterized, with N.E.P. of 10"16 watt Hert7/I/2.

• The system can be operated starting from temperaturesup to 10 K. This result is of great practical interest, as muchfor space applications as for use on 4-circIe diffractometers.Studies are being carried out to extend the system by usingstandard cryo-coolers and thus saving liquid Helium.

Cryomagnets

• During a loan to the LLB, the TAS magnet has showna permanent decrease of performance, from 6 Т to 4 T.Up to now the reason for this failure has not been identified.

• The two TASSE magnets (spin-echo) have been testedsatisfactorily, each for a period of one month. A system of dataacquisition and alarms is being developed, in collaborationwith the Instrumentation Branch.

• The Zeeman polarization cryomagnet has beencommissioned. Due to a leak, the cryostat had to be returnedto the factory (Oxford Instruments). The final performanceaccords with the specifications.

• The study of a small asymmetric split pair cryomagnethas been undertaken. A magnetic field of 2.5 Т or 3 Т isexpected, in a useful diameter of 50 mm, and a useful gapof 40 mm + 5° for the neutron beam divergency, the zero fieldpoint being out of the beam. This magnet would be mountedin a standard 'orange' cryostat. A call for tender has beenissued. First replies give a clear indication of the feasibilityat fairly low cost.

Temperature Measurement and Control

Development of the new ILLSEC (ILL SampleEnvironment Controller) has progressed. A prototype wasdelivered in the middle of 1993 and since then the softwarehas been advancing steadily and hardware modificationsmade as problems or errors were encountered. Somemanpower constraints mean that the projected deliverytimetable may be retarded but every effort is being madeto avoid this.

Contact has been made with the Laboratoired'Automatique de Grenoble and it has been agreed thata newly qualified engineer will spend six months at the ILLto help develop an auto-adaptive control algorithmspecifically designed around the ILLSEC. This will meanthat the instrument will take advantage of 'state of the art'control theory.

High Temperature - High PressureLaboratory

The activities of this group have been slowed downbecause the staff have been directly involved in the reactorrefurbishment project.

Furnaces

The optical (quartz) furnace has been terminated andtested. A new 2000 К furnace has been developed, builtand successfully tested. Three 2000 К furnaces togetherwith spare resistors have been built and delivered to HMIand PSI. Several experiments with ILL furnaces have beenperformed at LLB, HMI and DESY. Each timethe laboratory gave full technical support. A 1200 К furnaceincluding a 3 tonne uni-axiul pressure rig is underconstruction for the ILL Monochromator Group.

High Pressure Sample Environment

Pressure equipment has been lent to the Labor furNeutronenstreuung ETH Zurich, in particular pressure cells,a 15 kbar pump, an orange cryostat and a high pressureHe gas generator. During 1993 this equipment has allowedformer ILL users to perform experiments initially scheduledat ILL for summer 1991. One ILL technician and oneengineer were on leave several times to PSI in order to assistwith the use of the high pressure He gas generator.The results obtained have been published.

Instrumental Techniques (B. Hamelin)The aim of this group is to assess the efficiency

of essential instrument components by simple diagnosticdevices, to propose and design improvements of theinstrument performance and of its user-friendliness.We identify a variety of actions to focus our attention on:

• Analysis and better knowledge of neutron beamdivergence, spectrum and beam profiles;

• Improve sample-positioning techniques insideenvironment devices;

• More general use of neutron imaging techniquesto ease aligning, sample quality checks by on-line topography;

• Use of a novel y-ray imaging technique (patent Bastie,Hamelin) with a high-energy X-ray tube (200-400 keV)as a source. This allows quasi instantaneous volumecharacterization (mosaicity, parasitic grains) and easysample alignment and orientation, even inside a cryostat orfurnace. It will also prove valuable for the quick alignmentor checking of composite monochromators;

• More generalized use of modern roboticson our instruments.

The Instrumental Techniques Group offers help to allinstrument scientists to improve the performance andto optimize the use of beam-time of the instruments.

INSTRUMENTS - PROJECTS - TECHNIQUES

icncynostic>f théinc.ss.n:

>stie.

(orent

Coll. 9h - Fig. 5: SANS pattern (raw ilutii) of и semidihite/winner solution (polystyrene, Mn.=5I4000 g/mole,

solvent iïi-iiclylplithalate. concentration 9r/r n/ir.température 7=25 °C), measured at PAXY, LLIi. Solution

in laminar shear flow at a gradientof y =300 x~ ' (the light spot in thé mitlille

oj the detector is due to the primary neutron beam stop).See report p. 98.

-D.V- NFP - Fig. 3: The UCN source.See report p. 107.

^L• I^®

Mambo (I

Ф Storage Trap@ Prestorage \folume® Abtorblno Roof<X Pteton® MovabteSfctewallф DeadVbfcjme&• ShuttersС Entrance Guide® Neutron Guidéelà Detector for Stored NeutromОТ MonrtorE>etector

-DS- NFP - FIK. 4: Schematic view of MAMBO II.See report p. 108.

—DS- DIP F - Fig. 1: Ethane molecule inside ч zeolitecage visualised with the CERIUS cristallographie

software on one ofllie Diffraction Group Si/conGraphics Unix workstations. See report p. III.

-DS- DIFf - Hi-. 2: Data from a 'real-lime'experiment on Dill, where ч diffraction patternhas been collected every minute a.\ lite sampleundergoes a subtle phase transition on healing,as visualised in by Iris Explorer. See report p. III.

-DS- DIFF - Fig. 3: Iris Explorermaps of the unpaired electron

distribution in KrfMnOj)->fn»npolarized neutron diffraction data:

the maximum entropy re-construction(fig. h) eliminates the spurious

oscillations in the standard Fourierinversion (fig. a). See report p. III.

ci -colite'graphici/> Silt'on•I p. HI-

DPT - Fig. I A: Family photograph of the neutron guides team.From left to right: P. Ageron. W. Kaiser, J.L. Coquin, A. Cumin,R. Gamtelli, P. Labonne (C1LAS), S. Machicoisne (CIIAS).See report p. 128.

DPT - IB: Photograph of the new mechanical supportwith the seven HI guides. The two new cold neutron

guides NGI2 and NGI3 are on the left hand side.See report p. 128.

DPT- Fig. 3: The housing of the D20banana mull/detector opens in two pieces:Michel Bemeran stands at the sideof the front part on the final aluminiumsupport which will be used at D20mi a 'Tanzboden'; the back partis mounted on a special strong support(yellow) used during the constructionphase for the mounting of the 50 glassplates composing the 1600 cells,for their precise adjustment and forthe operation of closing the housing.See report p. 129.

DPT - Fig. 4: Results of finite element calculationsof the chopper disk of the TOF spectrometer IN5:

disk rotating at 20,000 r.p.m. with a window at theperiphery. Fig. 4a shows the stress distribution.

Fig. 4b shows the deformations. The window opensunder the effect of rotation by O.IK mm which is

unacceptable for the INS resolution.See report p. 131.

О/Т - Fig. 9: 2D diffraction profile (bottom)and ID projection {top) taken by high energy X-ray

diffraction of a Si/.xGef gradient crystalwith 0<x< 0.03. G is the reciprocal lattice vector.

The green line is a Lorentzian fit to the instrumentalresolution function. The red model calculation has an

arbitrary vertical scale factor. See report p. 136.

DP'/'-Пк. II: Werner Graf in /'millofilie new \puiirring facility n/ienitedin collaboration with the University oj /;Yn.See i'e/>tn'l />. 137.

Df'l - Fix. 12:

A view iiHiiilethe deposition chamberwith tin Argon pla.Miuiilluminating tile xnhstratecurrier. Нее report p. 137.

DPI - fit;. !•(•' Cryogenic le purifierjur luri>c ytianiitU'b к/ '//с.

II.I(Current I'ntvs)

/M - Table I:

The ILL Rtttiftt't 1979-1995.See rc/wrt p. /55.

m nm I.I.INIATS

a KKn,'«»i4HMi;NMC>IVH.MSA1U)

• INVKVIMhN'IS

D(ll'!-.KAriC)N4 if,

• STAH'UÎMS

'•] '/2 Vi 44

- REACTOR DIVISION -

The organisation of the DR remains essentially thesame as last year. In the following the main emphasis ison the reactor refurbishment. The Project Group acts asclient for the project and reports to the Head of theReactor Division. The complete structure is defined bythe following organisation chart.

Dismantling

Conditioning of the reactor block

The reactor block was removed from (he reactorswimming pool on 24 November 1992 (Fig. I) and placedon the cutting machine platform. Conditioning started inposition with the cutting off of the upper structure tubes withthe aid of special tools. This work continued during the

/•"/д. /: Transfer nftlic t/ltl rcacliir vessel to lite sltmtxe poolwith iisbislaiHV "JO. Hamiet, Л. Rimel, E. Manniiw,./. Correanl,M. Selvii../. l-'imml, M. Mollier.

- D R - DISMANTLING

whole of 1993. Fig. 2 shows the support which was locatedin the storage pool. The upper part of the machine wasdelivered and assembled during the first half of April and thecutting work on the reactor block started on 19.4.93 (Fig. 3).The cutting up eonti lued satisfactorily (Fig. 4). and wascompleted on 16.12.93 by the removal from ihe storage poolof the base flange of the reactor block (Fig. 5). At present

Fig. 2: The big turntable in the murage poi>l beforethe old reactor vessel was placed on it for cutting up.

there remains only the conical base of the reactor vessel,which will be positioned on a new platform and dealt with inthe storage pool early in 1994 (Fig. 6).

Waterproofing sleeves

The stainless .steel sleeves which cross the reactorswimming pool, separating heavy from light water, wereremoved after cutting up the bellows.

When the structures of the reactor block were removed,geometrical readings were taken of the position of the differentitems, waterproofing sleeve axis for the control rod, centre ofwaterproofing sleeves for the chimney and the cold and hotsources. These records are necessary at the reinstallation stageto ensure the immediate identification of the geometricaltolerances in relation to the previous system of axes.

Fig. 4: The cutting process in a very advanced state,a) The upper anti-turbulence grid covered with sawdust,h) The lower anti-turbulence grid, last piece to be removed.

Fig. 3: The cutting machine attacks the upper panof the reactor vessel.

-DR- DISMANTLING

sel.h in

torere

ed,•enlof

hotage'cal

Fig. 5: The bottom flange of the old reactor vessel wax taken mit in one piece. C. Sevos. G. Malouillot, J.L Beguet (from left to right).

Assistance and radiological records

Wherever there was a radiological risk, health physicsstaff gave continuous assistance in the operations. It may benoted that at all points involved in the work on the reactorthe human factor has been very important in obtainingpositive results.

Waste disposal

All the radioactive parts coming from the reactor zonewhich are not intended for réutilisation are treated asradioactive waste. Optimisation of the waste from cutting upand from processing of chips resulting from the cutting up isan everyday concern which requires intensive work andreflection in order to obtain satisfactory results.

Radiological results

The doses for the operators were low, correspondingto a small fraction of the legal limits.

Fig. 6: The' conical part of the reactor vessel.

-DR- RECONSTRUCTION

Reconstruction

In parallel to the work of removing the reactor structures,1993 was characteri/.ecl by the work of reconstruction andrenovation. The most important work concerned the reactorblock and the swimming pool.

Reactor block

The different parts of the reactor vessel are beingassembled to form the reactor block, which will be deliveredto ILL early in 1994. Over the year 1993 the reactor blockwas taking shape, identical to its predecessor, see front cover.

All the work took approximately 40 000 man-hoursduring 1993.

Turned-down grid

The hydraulic studies necessary to define a new anti-turbulence grid for the heavy water came up with a new'turned-down grid' design with the advantage of thepossibility of easy replacement by removing it from thereactor through a tube in the upper structure. This new «rid(Fig. 7) was installed in the reactor vessel duringconstruction together with the fuel element support.

Beam tube thimbles

The reconstruction of the beam tube thimbles (Fig. 8) isbased on recovery and re-machining in the ILL workshops(Fig. 9) of the rear parts recovered on dismantling and thewelding of the front parts (Fig. 10) as new replacements.This operation started again in April 1993. and finished inNovember 1993, and covered the production of 10 beamtube thimbles. For the remaining positions existing beamtube thimbles will be utilised.

/•'/.i;. Л': A hi'iim tube ihinible under leak test. J.I-'. Guriii-Ciichet.J. Pellegriim. J.I'. Gonellu. C. YUCCH:.

Fig. 7: The tumed-dmvngrid far lite ней' re.wl.

Fig. '/• Marc Liicalel/i in lite ILL workshop reshaping

a heiinitiihe iliiinhlf.

Coupling sleeves

The coupling sleeves are the link between the structureof the reactor vessel and the external flange sysiem. Afternumerous forming, welding and tensile tests on formedconvolutions and after metallurgical structure examinations,ordering and manufacture of the bellows have beencompleted. All the bellows have now been delivered.The manufacturing processes and the welding procedureshave been qualified and the initial deliveries are expectedearly in 1994.

-DR- RECONSTRUCTION

/•';.!;. 10ч: .1.1'. Gonella ami his colleague././•". Gitrin-Citchcl M'cltl/nt* ti betimliihe thimble.

/•7,1,'. lOh: Close-up of the welding procedure.

Reactor .swimming pool

As a preliminary to any work in the reactor

swimming pool, the lining has hccn

decontaminated (see Fig. 1 I ), the ambient

radioactivity being now very low, such that

manual work can be carried out without any

particular radiological protection.

The lining was inspected in February/

March 1993, and no significant defect was

found in its structure (Fig. 12).

rig. 11: The swimming pool lining under inspection.

Fig. 12: J.P. Ganlier-Maiirin. .1. Gangi. L. Melesi. K. Slmpiano.С Yocco- and li. I'oclel <it the bottom of the reactor swimmingpool after cleaning, lieamliolex can be seen in the background.

- D R - RECONSTRUCTION

I5e;mi tube H1/H2

The coupling sleeve, internal shielding and beam tubethimble were tested on a trial installation (Figs 13 and 14),followed by a hydraulic test of the H1/H2 swimming pool.The coupling sleeve is currently at the final machining stagefor length adjustment. The beam tube thimble is with themanufacturer for verification of leaktightness.

A new housing for the in-pile guides permittingthe installation of two additional cold neutron guides wasbuilt (see also the contribution in the chapter on the DPT,page 128).

Chimney

The manufacture of the new chimney is progressingnormally. The stainless steel part is currently at theultrasonic inspection stage, and the timetable and analyticalrequirements have been respected. The zirconium part willbe delivered in accordance with the overall timetable forreinstallation.

Stainless steel waterproofing sleeves

The waterproofing sleeves which ensure leaktightnessbetween the reactor swimming pool tank and the externalflange system have been cut up (Fig. 15), in order to changethe stainless steel bellows. The rear part has been recoveredand the nose flange welded and machined in the swimmingpool (Figs 16 and 17).

Fig. 13: Inner end of the H1/H2 beam tithe.

Fif>. 14: J.L. Durieit ami F. Sainl Sunlicc verify llie dimensions i>j'HI/H2 relative to a model of the reactor vessel.

- D R - RECONSTRUCTION

Work was completed in September 1993 with the replacementof the boral shielding on the noses and the hydraulic test of theswimming pool, which was completely satisfactory.

Painting of the reactor shell

Between August and November the metal shell changed itsappearance (Fig. 18). The sanding and the three coats of paint onthe external and internal parts were completed. Final acceptance of thework and pressurisation of the annular space took place inmid-December 1993.

Fig. IH: Repainting of the reactor shell.

Fig. 15: A new stainless steel bellows is welded to the outer purlof the beam tube by S. Millier anil F. Millier.

Fig. 16: P. Massafra weldingthe inner pun of a new stainlesssteel bellows from the swimmingpool side.

Fig. 17: F. Miiller verifyingthe dimensions of a beam tubein the reactor swimming pool.

Mechanical maintenance

In parallel with the replacement of the centralreactor structures, maintenance work on other partsof the installation, such as circuits, handlingsystems, safety devices and controls were carriedout in 1993.

Electricity, electronics

The long reactor shutdown has been utilised forcarrying out in depth maintenance on all theelectrical and electronic installations in the reactor.

A new electrical control installation forprimary and secon !ary beam shutters has beeninstalled for the neutron beams on guides HI, H2and H5. The racks for safety circuits, safely rodcontrols and high power safety circuits have beenreorganised and renovated.

Work is well advanced on a network toimprove fire detection and extinction in the reactorbuilding and the associated facilities.

-DR- STUDIES AND METROLOGY - BUDGET AND TIMETABLE

Studies and Metrology

Studies of metal seals

The parameters necessary to obtain leaktightness bycompression of metal seals (Fig. 19) have been determinedand fried out, and (he tightening procedures are now known,ILL having carried out these tests.

Modelling studies

Models of the hot and cold sources and patterns for thefuel element and safety rods have been built: these are usedfor the geometrical verification of the equipment of the newvessel.

Metrology

The geometrical checks on the beam tubes (Fig. 20) andof the reactor block support made it possible to go back tothe original tolerances with very satisfactory results. Theequipment used made it possible to transfer the coordinatesof the swimming pool site to the supplier of the new reactorblock for the machining and assembly of the reactor block(Fig. 21 ) before its despatch.

Fig. /9: Hydraulic tightening devices used to close the topof the new reactor vessel.

Fig. 20: Geometrical checks on the beam lubes by F. Saint Sapliceand G. Signoretti.

Fig. 21: F. Saint Snplice am! A. Rimet verifying dimensiims insidethe new reactor vessel.

Budget and Timetable

The budget approved by the Steering Committee for thereactor refurbishment project is still unchanged.

The timetable has been respected as a whole, and all themajor steps for the year 1993 were respected. A minor delayis anticipated for the delivery of the reactor block. Thetimetable for the restart of the reactor remains as originallyplanned at the date of July 1994.

- ADMINISTRATION -

DIVISION

Following the general development of the Institut, therewas a change in priorities for the Administration. Supportfor the refurbishment of (he reactor remained the main task,but during the year emphasis shifted to measures preparingthe resumption of the normal scientific programme with thereactor restart, in particular the implementation of personnelpolicy measures and the reorganisation of the Institut.

A new staff complement target of approximately 400 hasbeen accepted as the minimum necessary for normaloperation, and as the maximum possible within expectedcontributions to the budget. Measures to reach this goalincluded - for the first time in the Institut's history - alimited number of redundancies for economic reasons forstaff above a certain age level (56 years and 2 months)combined with an early retirement scheme. This stepenabled the Institut to proceed with the necessaryrecruitments, in particular in the scientific sector, which hasdecreased considerably in numbers under the non-recruitment policy introduced during the reactorrefurbishment.

The reorganisation of the Institut on 1.7.93 affected allsectors. Reorganisation took place in the middle of arunning budget year. While maintaining the old budgetstructure for the whole year 1993, responsibilities forexpenditure authorisations were redefined for the periodbetween 1.7. - 31.12.93, taking account of thereorganisation. This procedure proved to be effective.

In the course of the reorganisation the AdministrationDivision was augmented by a number of technical services(Telecommunications, Management Information Systems,Building and Site Maintenance). They were integrated intothe Division, which henceforth will be organised in fourservices:

- Finance and Management Information Systems (MIS):the MIS Group has been combined with the former FinanceGroup (budget, accounting).

- Purchasing: this sector which is also responsible for thestores, transport and customs, has now been organised as aseparate service.

- Personnel and Human Resources: in addition to itsprevious tasks, this service will now also be responsible forTelecommunications (telephone, fax).

- Building and Site Maintenance: this infrastructureservice has been transferred without affecting its internalstructure and purpose.

The Administration now comprises in addition to theareas of personnel and finance all the technical supportfunctions of a general character. Within the future total staffcomplement target of the Institut the Division will consist of63 staff.

The Division provided the secretarial for the twomeetings of the Steering Committee on 1/2 June 1993 inAbingdon (UK) and on 24/25 November 1993 in Grenoble.The Subcommittee on Personnel Questions met on 7 April1993 and the Subcommittee on Reactor Refurbishment hadthree meetings (4 March, 24 June, 18 October 1993).

The Head of the Administration continues to meetregularly with the Director of Administration of ESRF tosettle questions of common interest. There were also severalmeetings with EMBL representatives to prepare theextension of the ILL/EMBL building (ILL20), as planned byEMBL. The legal instruments for the extension have beenfinalised. Construction will start in 1994 and result in 800 to900 in2 of additional laboratory and office space for the useof EMBL. ILL and ESRF staff and users will havepossibility of access.

-DA- FINANCE AND MANAGEMENT INFORMATION SYSTEMS

Finance and ManagementInformation SystemsImplementation of the 1993 Budget

The first priority of the 1993 budget was the successfulcontinuation of the refurbishment of the reactor. The otheractivities of the Institut aimed at maintaining the existingscientific and instrument potential of the ILL, completing ofinstrument projects and preparing for the restart, in particularas regards the reinstallation of instruments. Totalexpenditure is expected to amount to 323.8 MF, comprisinga normal budget of 229.2 MF and the setting up of a reactorreserve of 94.6 MF, which alone represents 29 % of the totalbudget. It is assumed that 60.7 MF of this reserve will bespent in 1993, thus leaving a balance in the reserve of33.9 MF at the end of 1993.

The following table shows the changes in expenditurebetween 1992 and 1993:

Expenditure1992

MF %1. Staff costs2. Fuel elements

ConsumablesLong term suppliesand servicesShort term suppliesand servicesTravelMiscellaneousadm. costsTaxes and fees

3. OperationBuildingsEquipmentInstrumentsOther investments

4. Total Investments5. Normal Budget

173 7599926

70482038

9453557329502 133

11 7614937

241 039

Reactor refurbishment:6. Setting-up ( 6 5 4 0 0 )

of reserve7. Expenditure8. Balance of reserve

at end of year9. Additional reserve10. Total expenditure

(S + 7 + 8 + 9)

2943309 382

56.23.25.1

2.30.7

0.311.50.90.73.81.67.0

1.0100.0

Estimatedexpenditure

1993MF %

167 5617700

77981 797

137436095

108895297

229 237

(94 600)

51.72.44.8

2.40.6

0.411.20.00.53.41.65.5

-323837100.0

Change92/93

-22.4-1.8

10.6-11.8

45.41.5

-100.0-20.5-7.47.3

Staff costs diminished by 3.6 % compared to 1992 as adirect consequence of the personnel policy initiated by theManagement in order to adjust to the particular situationduring the refurbishment and to prepare for the resumptionof normal scientific work after the reactor restart in 1994 (cf.section on personnel management and human resourcesbelow). The total staff in post decreased from 421 at the endof 1992 to 382 at the end of 1993.

Fuel costs were reduced by 22.4 % compared to 1992,because there was less expenditure for the interim storage ofthe 18 irradiated fuel elements at Cadarache (where majorexpenditure on storage facilities had occurred in 1992). Fuelelement production remained at 1 element per year. As in1992 there were no new uranium purchases, nor expenditurefor reprocessing.

Taking account of the reactor shutdown and the absenceof scientific experiments, operation costs remainedessentially at the same level as in 1992. The slight increaseof approx. 1.5 % compared to 1992 can be explained by anincrease in taxes and additional expenditure for thereinstallation of instruments.

Investments within the normal budget decreased by17.9 % compared to 1992. This decrease is due to a largeextent to the building sector where after the completion ofthe guardpost and the joint ILL/ESRF building in 1992 nonew projects were undertaken. Scientific investments werereduced by 7.4 % to 10.9 MF; main investment projectswere IN4C, PN2 (GAMS5), beamlines H1/H2 and thedevelopment of the polarized 3He filter. The increase of7.3 % in the sector of "other investments" is due mainly tothe UNIX conversion programme in computing.

As planned, the implementation of the 1993 budgetpermitted the setting-up of a reserve of 94.6 MF for therefurbishment of the reactor of which 60.7 MF will be spentin 1993, thus leaving 33.9 MF at the end of the year to becarried forward. The Management expects that theanticipated overall external expenditure of 173.1 MF for therefurbishment of the reactor will be respected. The projectwill be finished in 1994. Expenditure in 1994 is fullyfinanced by the carry-forward of the reactor reserveremaining from the years 1991, 1992 and 1993.

The normal budget decreased from 241.0 MF in 1992 byabout 5 % to 229.2 MF in 1993. This decrease affectedparticularly staff costs, fuel elements and investments,whereas operation costs increased slightly.

EMS -DA- FINANCE AND MANAGEMENT INFORMATION SYSTEMS

Income - Comparison of 1992 and 1993 Budgets

Income

Collaborationwilh ESRFILL's own incomeSpanishcontributionSwisscontributionAustriancontributionAssociates'contributionsCarry forward92/93Utilizationof interestAdditional carryforward 92/93Total

Income1992

146911 6874650

287 250

- 1 874

309 382

0.53.81.5

EstimatedIncome

1993MF %

1 45030934859

304 062

323 837

0.41.01.5

Change

-1.3-73.5+ 4.5

The contributions of the Associates amounted to 304 MFwhich represented approx. 94 % of the ILL income. Amongthe scientific members, Switzerland did not prolong itscontract with the ILL in 1993, due to the reactor shutdown.Negotiations for a new contractual basis with scientificmembers - Austria, Spain ar.H Switzerland - after 1.1.94have been held in 1993 an.: !!•£ respective contracts areexpected to be signed soon.

As regards other sources of income, the 73.5 % reductionin "ILL's own income" resulted from the request of theAssociates - following the practice at ESRF - to distributeinterest earned by the Institut to the Associates, unless theSteering Committee decides to allocate them to the annualbudget. The Associates, however, allow interest earned onparticular funds (e.g. reactor reserve) to be credited to therespective fund, and in 1993 they also agreed that 3.9 MF ofinterest should be used to finance additional expenditure forthe early retirement plan within the normal budget.

Forward look

The year 1994 is characterized by the completion of thereactor refurbishment project, the preparation for theresumption of the normal scientific programme, includingreinstallation of instruments, the actual restart of the reactorin the middle of 1994 and the pursuit of the personnelpolicy, including the early retirement programme and amajor recruitment effort in the scientific sector. The 1994budget adopted by the Steering Committee on25 November 1993 with a total of 346,6 MF comprises anormal budget of 264,0 MF and expenditure for therefurbishment of the reactor of 73,7 MF.

Overall survey: the ILL Budget 1979 -1995

Table 1 (page 144) gives a survey of the development ofthe ILL budget between 1979 and 1995 at current prices,according to categories of expenditure. For 1994 theapproved budget and for 1995 the proposed draft outlinebudget have been used. The survey shows in particular howexpenditure in the normal budget (staff costs, investments,operation and fuel) has been reduced since 1991 to facilitatethe financing of the refurbishment of the reactor.

Management Information Systems

In the framework of the reorganisation on 1.7.93 theManagement Information Systems Group was transferredfrom the former Computing Department to theAdministration Division where it is part of the Finance andManagement Information Systems Service.

On the technical side, the continued implementation ofthe UNIX plan in the context of the client-server architectureled to the installation of a new HP/UX server, the shutdownof the MISSILL system (based on an old PDP11), theintroduction of an increasing number of PCs, incorporatingword processing functions and access to data bases, while thestock of Macintoshes remained almost unchanged.

As regards applications, the interest of the "site" base ledto an increase in the number of access points (ILL andESRF) and the gradual connection of dependent applications,particularly in the fields of personnel management, medicalsurveillance and scientific work. Other developments havebeen implemented using PC software such as Excel, Paradox,Access, etc.

In the future a major task of the Management InformationSystems Group will consist in the introduction of a newsoftware system package for the finance/budget/ purchasingsector. Preparatory work for this programme will start in 1994.

- D A - PURCHASING

PurchasingThe Purchasing Service was involved in all commercial

aspects of the reactor refurbishment project, and negotiated anumber of other purchases mainly in the scientific andtechnical sectors.

Reactor Refurbishment

Purchasing continues to cooperate closely with theProject Group for the reactor refurbishment. In March, twomajor orders for the coupling sleeves of the reactor wereplaced; one half with ROLLS ROYCE THOMPSON (GB)and the other half with NEYRPIC FRAMATOMEMECANIQUE (F). The bellows which will be fitted to thecoupling sleeves have been ordered from WITZENMANN (D).

The last major orders for the refurbishment of the reactorwere approved by the Subcommittee Refurbishment in June1992. These three orders were placed as follows:

- WORMALD (GB) for the fire protection system,

- FORWARD INDUSTRIES (GB) for the centralchimney,

- BARRIER (GB) for painting of the reactor building.

Several orders of smaller value were placed, notably, thenuts and bolts for the reactor block have been ordered fromAUBERT et DUVAL (F). The contract for the manufactureof the folded-down grid and its diffuser was awarded toGIROD SISA (F); the grid was sent to ZEPPELIN (D) forassembly into the reactor block.

Other purchases

Other major purchases for the Reactor Division werefinanced from the normal budget; NOELL (D) were awardedthe contract to refurbish the rail of the overhead crane inlevel D of the reactor building. The control system of thereactor will be completely replaced; BULL (F) were selectedfor supply of the computer system and SIEMENS (D) for theprogrammable controllers.

The in-pile mechanical parts of the neutron guides HI -H2 will be replaced before the re-start of the reactor. PINKENGINEERING (GB) was selected for the manufacture ofthese parts.

For the instruments, the most notable purchases were forthe high priority "time of flight" neutron spectrometer IN4C.GLACIER (GB) won the order for the magnetic bearingsuspension systems for 1N4C neutron choppers, whereas themotors for these choppers are being supplied by AUX1LEC (F).

In the Computing area, the acquistion of a DEC - alphamachine was most significant. By stopping the maintenancecontract on the VAX 8700 the resulting savings are beingused to lease the DEC - alpha computer thereby maintainingthe central computer services' capacity for VAX-VMSprocessing and allowing a smooth transition to UNIX.

Distribution of purchases in the member states

Whenever possible, for major purchases, an internationalcall for tenders was carried out; offers were compared on anex works basis so as not to disadvantage British and Germanfirms compared with local suppliers. This, together withnegotiation of discounts from regular suppliers for routinepurchases, enabled us to achieve considerable savings.

The distribution of ILL purchases (orders exceeding50 KF) in the first 10 months of 1993 is shown below.The figure includes purchases for which a free choiceof suppliers was possible excluding therefore the fuel cycle,electricity and small purchases less than 50 KF. To enable acomparison, the relevant figures for 1992 are also indicated.The fluctuations between 1992 and 1993 can be explainedby major purchases for the refurbishment project.

Distribution of ILL purchases (orders > 50 KF)

France

Germany

United Kingdom

Others

Transport and Customs

The Single European Market came into force on1st January 1993 thus removing customs controls at theborders within the EEC. This has allowed a freer movementof goods within the Community, but companies now have todo monthly declarations of all their arrivals and despatcheson a standard form which is submitted to the customsauthorities. After some teething probiems, the system worksvery well, and we are now considering installing acomputerised system for these monthly declarations.

Stores

A new and more efficient system for the supply of officestationery was introduced in 1993. Suppliers now deliver thegoods directly to the secretaries' offices every fortnight;consequently there is now virtually no stationery held onstock in the stores.

During 1993 ESRF has set up its own store and thereforeno longer relies on ILL's general store. ESRF does,however, continue to use ILL's raw material store with itsspecial cutting equipment.

-DA- PERSONNEL AND HUMAN RESOURCES

Personnel and HumanResources

The Personnel and Human Resources Service consists ofthree groups. Personnel Management, Human Resources and- since the reorganisation of 1.7.93 - Telecommunicationsand General Services.

Personnel policy

Personnel policy was determined by the aims ofsupporting the refurbishment of the reactor, delevopingscientific expertise and controlling the staff costs budget. In1993 the emphasis moved to measures preparing for normaloperation after the reactor restart.

The Institut continued to involve its staff as far aspossible in the refurbishment of the reactor. This concernedin particular the staff of the Reactor Division, but in manyinstances also staff from other Divisions. In addition 24 staffwere transferred internally to support the refurbishment orperform other important in-house tasks. These measureshelped to retain staff, to enhance motivation and to controlthe external refurbishment costs.

Concerning the development of technical expertise theManagement encouraged the secondment or detachment ofscientists and technicians to other research centres (inparticular ESRF, CNRS, LLB, HMI, NIST) and in somecases to industry (e.g. SGS-Thomson, Pechiney). Overallthere were 38 cases of detachment or secondment which alsohelped to make considerable budgetary savings.

Since the beginning of the refurbishment project theManagement had initiated a policy of facilitating naturaldepartures to control staff costs. This policy was alsoconfirmed by the consideration that the Institut, in view ofthe expected contributions after the reactor restart in 1994, isobliged to aim at a new staff complement target ofapproximately 400 (compared to 483 staff in post at the endof 1990). As a final step within a whole range of measures toachieve this target and to ensure a balanced composition ofstaff to operate the Institut, the Management proposed a planfor a limited number of redundancies for economic reasonstogether with an early retirement plan ("Convention FNE -Fonds National pour l'Emploi"). This plan was approved bythe Steering Committee on 2 June 1993 and the Conventionwith the Labour Authorities was signed on 23 June 1993.During 1993 14 staff members aged between 56 years 2months and 60 left the Institut under this scheme, and furtherdepartures are planned for 1994. A further 8 employeesbetween 55 and 60, who had done shift work, took earlyretirement according to specific rules in 1993.

The resulting overall staff changes and the situation on31.12.93 are given in the tables 2 and 3. Recruitment in 1994and 1995 is essentially aimed at the scientific sector.

Staff complement situation at 31.12.1993

Staff movements in 1993 have slightly changedthe breakdown by nationalities (numbers in brackets indicatethe situation in 1992):

French

German

British

Others

64.8 % (63.2 %)

15.5% (16.4%)

12.8% (14.7%)

6.9 % (5.7 %)

Far a comprehensive survey see Table 3.

Average age

The average age at ILL on 31.12.93 was 44.7 years.Table 4 shows the breakdown by age and staff category.

Salaries

A salary agreement was signed by the Management withthe SA-ILL and FO unions on 4 May 1993 providing forgeneral salary increases in 1993 as follows:

1 % on 1 May 1993

1.6% on 1 December 1993

A meeting of the signatories will be held at the beginningof 1994 to review the application of this agreement. Anadjustment may be made as a function of the generaleconomic trends and the situation of the ILL.

3501990 91

Table 2: Staff movements.

93 94 95end of year

96 97 98

-DA- PERSONNEL AND HUMAN RESOURCES

DIRECTOR'S SERVICES

SCIENCE DIVISION

PROJECTS &TECHNIQUESDIVISION

REACTOR DIVISION

ADMINISTRATIONDIVISION

Staff at 3 1 . 12.92

DIFFERENCE 92/93

CADRES

AverageAge

THESIS STUDENTS

AverageAge

NON-CADRES

AverageAge

G: German, В: British, F: French, О: Others, Т: Total

Table 3: Staff complement situation at 31.12.1993

Professional training

French legislation requires employers to assist infinancing professional training, and 1.5 % of the payrollmust be devoted to training costs. Part of this percentage ispaid directly to the State as a contribution to the organisationof courses for young people and also to finance the systemof leave for training. The majority of training provided inthis context for ILL staff consisted of language and technicalcourses. In 1993 the conversion to the UNIX systemrequired a specific training effort for computing staff andusers. In 1993, 205 staff attended training courses.

International schooling

Schooling for children continues to be an essential pointin the integration of families. ILL and the other employersconcerned in Grenoble, including ESRF, have set up anAssociation (Association pour le Développement del'Enseignement International dans la Région Grenobloise -ADEIRG) to develop and improve the system of'international sections' set up by the French Ministry ofEducation. The purpose of this Association is to be a singlerepresentative spokesperson vis-à-vis the EducationAuthorities, and to permit a frank dialogue on individualcases and questions such as the contracts of the teachersin this system.

a= 80Stn

Ъ 60-f 40

a cadres• thesis students• пол-cadres

21-25 26-30 31-35 3640 4145 46-50 51-55 5 Ш 61-65a g e interval l

Table 4: Breakdown by age and category at 31.12.1993

Communication

There have been two issues of the magazine 'La Boîteà Neutrons' in 1993. The subjects covered are connectedwith research, know-how and other subjects of generalinterest at ILL.

Telecommunications and General Services

The Joint Telephone Service continued to provideILL and ESRF with te lephone l ines . The ILLradiotelecommunication systems have been modernised togive users a better and more efficient service.This group alsoprovides a number of general services to facilitate the workof all staff as regards post, reprographics, photocopiers,errands in town, etc.

-DA- BUILDING AND SITE MAINTENANCE

Building and Site Maintenance

The Building and Site Maintenance Service is in chargeof the maintenance and modifications of the ILL site,buildings, technical installations (except the reactor) andexperimental positions. Its purpose is to provide thenecessary technical support in this field to all sectors of theInstitut. Under the new management structure implementedon 1.7.93 the Service is attached to the AdministrationDivision.

Maintenance, Repairs and Improvements

The areas concerned are: ILL site (roads and car parks,fences, drainage system and open spaces), buildings(structure and fittings, waterproofing) and technicalinstallations (electricity, plumbing, heating, ventilation, airconditioning, handling) associated with buildings andexperiments. Systematic maintenance is planned to preventbreakdowns, repairs are executed to minimize "down time"and improvements are made to increase reliability. Theinterventions are carried out by the group's workshops or byexternal contractors.

The Service also supervises the cleaning of buildings andopen spaces, the clearing of snow and waste removal, thesupply of furniture. Due to the reorganisation it had toorganise and carry out many transfers of offices.

Constructions and Modifications

The Service designs and follows up the construction,renovation and modification of buildings, offices,laboratories and technical installations. In 1993 the Servicewas strongly engaged in the work for the refurbishment ofthe reactor. It supervised the repainting of the interior andthe exterior of the steel shell of the reactor. It also managedthe renovation of rails and structures of the main crane in thelevel D of the reactor building. The workshops of theService, in particular the main sheet metal workshop, arecontinuously carrying out specific tasks for therefurbishment project.

To prepare the restart of the scientific programme, theService installed new safety barriers around the experimentalpositions, carried out a renovation of the electricaldistribution on these positions and constructed shielding forIN4C, EVA, ADAM and PF1. The Service will continue toparticipate in the reinstallation of instruments.

Another important project was the installation of the newpremises for the joint ILL/ESRF Medical Service.

- COMMUNICATIONS -

SeminarsCollege 2

Theory"Quasiparticle currents in one dimensional Peierls and

Hubbard models".S. MATVEENKO, Landau Institute, Moscow, Russia.

"Quantum localization transitions in generalized polaronmodels".J. PALMERI, ILL, Grenoble, France.

"Liquid helium films: structure, growth and dynamics".B. CLEMENTS, ILL, Grenoble, France.

"Electrons in magnetic fields".I. VAGNER, SNCI, CNRS, Grenoble, France.

"Théorie de gap de spin dans les supraconducteursà haute Te : discussion des expériences de diffractionneutronique et de RMN".M. LAVAGNA, DRFMC/MDN, CEN-Grenoble, France.

"Unified approach to the charge/spin density waveselectrodynamics".S. BRAZOVSKII, Landau Institute, Moscow, Russia.

"Treatment of recoil in neutron scattering from classicalsystems".G.R. KNELLER, DBCM-SBPM, CEA-Saclay, France.

"Order by disorder and spin origami in stronglyfluctuating magnetic systems".E. SHENDER, University of Ottawa, Ontario, Canada.

"Spin supercurrents in He В under an electric field".V.P. MINEEV, Landau Institute, Moscow, Russia.

"Ondes de densité de charge bipolaroniques".P. QUEMERAIS, ILL, Grenoble, France.

"Enroulement et localisation d'une chaîne polymère:influence des interactions chirales".B. HOUCHMANDZADEH, Spectrométrie Physique,Université Joseph Fourier, Saint-Martin-d'Hères, France.

"Crossover from BCS superconductivityto Bose-Einstein condensation".R. HAUSSMANN, Univ. Miinchen, Germany.

"Superconductivity and superfluidity in Fermi systemswith repulsive interactions".M. KAGAN, Kapitza Institute, Moscow.

"First principle theory in alloy surfaces".A. PASTUREL, Maison des Magistères, Grenoble, France.

"Vérifications expérimentales des états polaroniques".J. RANNINGER, CRTBT, CNRS, Grenoble, France.

"Two dimensional crystallization of organic moleculesat the water surface".B. BERGE, Spectrométrie Physique, UniversitéJoseph Fourier, Saint-Martin-d'Hères Cedex, France.

"Sum rules and angular dependence in photoemission".B. THOLE, Univ. de Groningen, Germany, and ESRF,Grenoble, France.

"Finite size magnetization and scaling behaviourin 2D x-y magnets".P. HOLDSWORTH, ENS, Lyon, France.

"Reversible plasticity and surface phenomenain perfect crystals".A.F. ANDREEV, Kapitza Institute, Moscow, Russia.

"X-ray dichroism: more sum rules".P. CARRA, ESRF, Grenoble, France.

"Exact map of Kondo impurities onto a semiinfinite chain".N. SCHOPOHL, CRTBT, CNRS, Grenoble, France.

"Metals in a high magnetic field: a new universalityclass of marginal Fermi liquids".V. YAKOVENKO, Rutgers University, New Brunswick,NJ, USA.

"Negative U extended Hubbard model for doped bariumbismuthates".A. TARAPHDER, NEC + LEPES, CNRS Grenoble, France.

S EM I N ARS

"Modèle de Hubbard avec intégrale de saut dépendantde l'occupation des sites".M. AVIGNON, LEPES, CNRS, Grenoble, France.

"Superconductivity in incommensurate crystals".V.P. MINEEV, Landau Institute, Moscowand CEN-Grenoble, France.

"Singularités dans les écoulements incompressibles".T. DOMBRE, CRTBT, CNRS, Grenoble, France.

"Renormalization effects of vortex fluctuationsin layered superconductors".S. SCHEIDL, Univ. Munchen, Germany.

"Vortex bidimensionnels et lignes de vortexdans les supraconducteurs lamellaires".D. FEINBERG, LEPES, CNRS, Grenoble, France.

"Conductivity peaks broadening in the quantumHall regime".B. SHKLOVSKI, Univ. of Minnesota, USA.

"Hydrodynamics of density wave crystals".S. BRAZOVSKÎI, Landau Institute, Moscow and ILL,Grenoble, France.

"Achille, la tortue et la croissance des cristaux".J. VILLAIN, DRFMC/SPSMS/MDN, CEN-Grenoble,France.

"Pinning phenomena in superconductors".A. LARKIN, Landau Institute, Moscow and CRTBT,CNRS, Grenoble, France.

"Statistics of conductance fluctuations in quantum dots".K. EFETOV, M.P.I. Stuttgart, Germany.

"Liquides de spin sur le cactus de Husimi".B. DOUÇOT, CRTBT, CNRS, Grenoble, France.

"Nearly ideal 2D Fermi gas in a magnetic field".Y. BYCHKOV, Landau Institute, Moscow, Russia.

"Le mouvement Brownien retrouvé, ou, commentcalculer correctement le coefficient de frictionhydrodynamique".J.P. HANSEN, ENS, Lyon, France.

"Paired electron crystal in the low densityelectron limit".K. MOULOPOULOS, LEPES, CNRS, Grenoble, France.

"Breakdown of Fermi liquid beyond 1 dimension".P.A. BARES, ILL, Grenoble, France.

"Points de Néel et ondes spirales dans un cristal liquide".P. COULLET, Institut Non Linéaire, Nice, France.

"The s-wave, d-wave controversy in high temperaturesuperconductors".C.M. VARMA, A.T. and T. Bell Laboratories, Murray Hill,NJ, USA.

"Ab initio molecular dynamics studies of fullerenesand fullerides".W. ANDREONI, IBM, Zurich, Switzerland.

"Light ys electrons: a survey of multiple scatteringtransport".B. van TIGGELEN, Maison des Magistères,Grenoble, France.

"Ising simulations and nucleation in cellular automata".G. GOMBOS, Res. inst. for Techn. Physics, Budapest,Hungary.

"Formation de structures organisées à l'état solideen métallurgie physique: exemples et nouvelles approches".Y. BRECHET, LTPCM, Grenoble, France.

"Le modèle de Hubbard à 2D à faible remplissage de banH<>"Anne-Marie DARÉ, Univ. de Sherbrooke, Canada.

Collège 3

Fundamental and Nuclear Physics"Recent experiences in preparing to dismantle

a nuclear reactor".C. BATES, University of Liverpool and Manchester, UK.

"Ultra-cold neutron projects at pulsed sources".A.V. STRELKOV, J.I.N.R., Dubna, Russia.

"Production of defects by neutrino recoil observedby perturbed angular correlation".R. SIELEMANN, HMI, Berlin, Germany.

"Space and time reversal symmetry violationand polarized eV neutrons".Yasuhiro MASUDA, KEK, Japan.

"Progress report on the implementationof a thermal ion source at the ILL (PIAFE)".H. FAUST, ILL, Grenoble, France.

"Instrument neutron activation analysis at S51".R. OLIVER, ILL, Grenoble, France.

"Antiprotonic X-rays as a probe of the hadronic interaction".G. BORCHERT, KFA Jiilich, Germany.

"Error assessment for future neutron lifetimemeasurements with MAMBO H".V. NESVIZHEVSKY, PNPI, Saint-Petersburg, Russia.

"A simple phenomenology of pre-collective nuclei".N.V. ZAMFIR, Brookhaven Nat. Laboratory,Upton, LI, USA.

"Probing low-energy collective nuclear modeswith the inelastic neutron scattering reaction".S.W. YATES, University of Lexington, Kentucky, USA.

SEMINARS

"A future for electron spectroscopy at the ILL".W.D. HAMILTON, University of Sussex, UK.

"Ion beam mixing of metal/metal and metal/Nitridelayers - New perspectives".K.P. LIEB, Univ. Gôttingen, Germany.

"A tuneable monochromatic y-ray sourceat the Gent Linac".J. JOLIE, Univ. de Fribourg, Suisse.

"Recoil-ion momentum spectroscopy: a new toolto probe collision induced atomic reactions".J. ULRICH, GSI Darmstadt, Germany.

"Multilayer mirror interferometer for cold neutrons".Y. OTAKE-TAKAHARA, Kyoto Univ. Japan.

"Quality and availability of highly enriched actinideisotopes at VNIIEF".S. VESNOVSK1, All Russia Scient. Res. Inst.for Exp. Phys. Arzamas-16 (VNIIEF) Russia.

"The capability of the high flux pulse reactor BIGR(Arzamas - 16) for high density UCN production.V. SHVETSOV. A. STRELKOV, JINR Laboratoryof Neutron Physics, Dubna, Russia.

College 4Structural and Magnetic Excitations

"On the valence of Praseodymium in Pr-Ba-Cu-O".V. NEKVASIL, Czechoslovak Acad. of Sciences, Prague,Czechoslovakia.

"Investigation of phonons in Cr-iO^ on the PRISMAneutron T-O-F spectrometer".T. MAY, Univ. Regensburg, Germany.

"Statics and dynamics in a model for modulatedphases in AiBX4 systems".T. JANSSEN, Univ. of Nijmegen, The Netherlands.

"Fast convolution in four dimensions: a new methodfor the interpretation of neutron scattering data".W. SCHMIDT, ISIS, Rutherford Appleton Laboratory, UK.

The problem of the convolution of the Lorentzianand the Lorentzian squared with the resolution function.J.E. LORENZO, Brookhaven Nat. Lab., USA.

"Neutron scattering study of CsFeClj and CsFeBrçin external magnetic fields".B. SCHMIDT, ILL, Grenoble, France.

"A Monte-Carlo study of magnetic phase transitionson an FexMg].xCb model. From pure metamagnetto random field behaviour".Laura HERNANDEZ, Inst. Nat. Sci. Appliquées,Toulouse, France.

"Phase transitions in disordered Perovskite-Iikesingle crystals".S. VAKHRUSHEV, A.F. loffe Physico-Technical Institute,St. Petersburg, Russia.

"Some structural and electronic propertiesof monomolecular organic layers on semiconductors".B.A. NESTERENKO, Acad.of Sci. of Ukrainia, Kiev,Russia.

Lattice dynamics and Fermi surfaces in metalsand alloys investigated by neutron inelastic scattering".A. IVANOV, Kurchatov Institute, Moscow, Russia.

"Recent advances in lattice dynamics".D. STRAUCH, Universitat Regensburg, Germany.

"X-ray and neutron diffraction analysis of dislocationstructures in polycrystals".P. KLIMANEK, TU Mining Academy Freiberg, Germany.

"Antiferromagnetic rare-earth ordering in the high-Tc

superconductors Rba2Cu3Ox (R = Yb, Ho), RBa2Cu4O8

(R = Ho, Dy) and spin-wave excitations in Bi?CuO4".B. ROESSLI, Paul Scherrer Institut, Villigen, Suisse.

"Investigation des verres protoniques Rb].x(NH4)x

H2PO4 avec T12+ par résonance magnétique électronique".V. IZOTOV, Univ. de Kazan, Tatarstan, Russie.

"Influence of dilution on the critical behaviour in thefrustrated 3D Heisenberg system CdCr2(1_x)In2xs4"-Stéphanie POUCET, ILL, Grenoble, France.

"Magnetic ordering and excitations in quantumantiferromagnets".A. HARRISON, Univ. of Edinburgh, UK.

College 5Crystal and Magnetic Structures

"The first steps in a new dimension: an introductionto the silicon graphics workstation of the diffraction group".A. HEWAT, ILL; G. McFNTYRE, ILL; A. FITCH, ESRF;F. TASSET, ILL, Grenoble, France.

"Incommensurate magnetic systems:a quantitative analysis".D. SCHMITT, Laboratoire de Magnétisme Louis Néel,CNRS, Grenoble, France.

"Flashes of Science" (I):"The magnetic phase transitions of MnWO4".G. LAUTENSCHLÂGER, ILL, Grenoble, France.

"The investigation of the surface superconducting regionin lead films using polarized neutron reflectivity".M. NUTLEY, ILL, Grenoble, France.

"X-ray diffuse scattering from rough suinterfaces and volume defects".V. HOLY, The Masaryk University, Czechos.o, "da.

SEMINARS

"Neutron backscattering from vibrating silicon crystals".R. HOCK, Univ. of Wiirzburg, Germany.

"Flashes of Science" (II):"Magnetic structures of R2BaNiO5 compounds(R = rare earth)".E. GARC1A-MATRES. ILL, Grenoble, France.

"Etude du magnétisme des composesCe2Fe,7Hx (x = 0:5) and Ce2Fe17N3".O. ÎSNARD, ILL, Grenoble, France.

"X-ray scattering from epitaxial multilayersand surface gratings".G.T. BAUMBACH, ILL, Grenoble, France.

"X-ray and neutron scattering studies of oxygen orderingin YBA2Cu206+x".V. PLAKHTY, PNPI-CEN-Grenoble and St. PetersburgNuclear Physics Institute, Russia.

"Electron and nuclear densities from maximum entropymethod analyses of X-ray and neutron diffraction data".C. HOWARD, ANSTO Lucas Heights ResearchLaboratories, Australia.

"Quantum theory of giant magnetoresistancein multilayered structures".A. VEDYAYEV, DRF, CEN-Grenoble, France,and Moscow University, Russia.

"Magnetic properties of ternary phosphideswith ThCr2Si2 - and Zr2Fe12P7 - type structure".M. REEHUIS, Hahn-Meitner-Institut Berlin, Germanyand ILL, Grenoble, France.

"Neutun scattering from cubic ZrO2".D.N. ARGYRIOU, Australian Nucl. Sci. and Tech.Organisation, Menai, Australia.

"Symmetry analysis of magnetic structuresof R2CuO4 (R = rare earth)".I.M.VlTEBSKY, Inst. for Single Crystals,Ukrainia Acad. of Science, Russia.

"How I spent my summer holidays - part I":"Straight from the Seoul", A. HEW AT."Nipponese neutrons". C. ZEYEN."Neutron optics with bent perfect crystals".J. KULDA, ILL, Grenoble, France.

"Surface anisotropies in epitaxial thin iron (110) films".O.Mc GRATH, Lab. Louis Néel, CNRS, Grenoble.

"Numerical methods in micromagnetics: determinationof the magnetic structure in ferromagnets".D.V. BERKOV, Inst. of Chem. Phys. Chernogolovka, Russia.

"Applications of non-contact ultrasound".S.P. PALMER, Univ. Warwick, UK.

College 6Liquids, Disordered Materialsand Metal Physics

"Density expansion spectroscopy:light and neutron scattering".F. BAROCCHI, Univ. di Firenze, Italy.

"Structural studies of highly corrugated surfaceswith He-beam diffraction".E. KIRSTEN, MPI fur Stromungsforschung,Berlin, Germany.

"Lattice dynamics of three dimensional quasicrystals".P. GALLO, Univ. dell'Aquila, Italy.

"|iSR studies of hydrogen in metals".F.N. GYGAX, ETH Zurich and PSI Villigen, Switzerland.

"Relaxation in glycerol:Do neutrons and light see the same ?"J. WUTTKE, TU MUnchen, Garching, Germany.

"Progress Report on Be".C. MAY, ILL, Grenoble, France.

CollegesBiological Structures and Dynamics

"Protein structure: analysis, prediction and design".J.M. THORNTON, Univ. College London, UK.

"Une nouvelle famille de protéines riches en cystéines:structure et modélisation".F. BAUD, ILL-IBS, Grenoble, France.

Collège 9Chemistry

"Neutron reflectivity and surface tension studyof a diblock copolymer at the surface of a selective solvent"B.J. FACTOR, Institut Curie, Paris, France.

"Microstructure and rheology of soft matter -Investigations using neutron scattering and othertechniques".J.D.F. RAMSAY, Institut de Recherches sur la Catalyse,CNRS, Villeurbanne, France.

"On thé application of polymer theoryto giant worm-like lecithin microemulsions".P. SCHURTENBERGER, ETH Zurich, Switzerland.

"Weakly charged polyelectrolytes".F. SCHOSSELER, Université Louis Pasteur,Strasbourg, France.

"Fullerene intercalation chemistryand superconductivity".M.J. ROSSEINSKY, Inorganic Chemistry Laboratory,Univ. of Oxford, UK.

SEMINARS

"Laminar and turbulent flow behaviourof viscoelastic surfactant solutions".H.W. BEWERSDORFF, Swiss Federal Instituteof Technology, Zurich, Suisse.

"Structural and spectroscopic studiesof rare earth oxy compounds".J. HÔLSÀ, University of Turku, Finland.

"SANS and neutron reflectivity studiesof grafted copolymers".W. DOZIER, Argonne Nat. laboratory, USA.

"Rotational tunnelling of ammonia molecules".M. HAVIGHORST, IFF, KFA, Jiilich, Germany.

"Inelastic neutron scattering studiesof the proton transfer dynamic in high region bonds".F. FILLIAUX, LASIR-CNRS, Thiais, France.

"An introduction to Bayesian model selection".D. SIVIA, RAL, Didcot, UK.

Thursday colloquium"L'organisation spontanée dans les plantes

vers des structures cristallines particulières".S. DOUDAY, E.N.S. Paris, France.

"Modèles statistiques de l'évolution Darwinienne".L. PELITI, Institut Curie, Paris, France.

"Physical properties of ultra thin films investigatedby X-ray reflectivity".J.J. BENATTAR, SPEC, CE Saclay, Gif-sur-Yvette, France.

"Nuclear magnetic ordering in metals".F. POBELL, Univ. Bayreuth, Germany.

"The complex Ginzburg Landau approachto nonequilibrium pattern formation".Wim van SAARLOOS, Leiden University, The Netherlands.

"High-Tc superconductors:Present status of applications".H. RIETSCHEL, Kernforschungszentrum,Karlsruhe, Germany.

"Fluids in space".D. BEYSENS, SPEC, CE Saclay, Gif-sur-Yvette, France.

"Giant, micelles, fluid membranes and reversiblyconnected networks: towards a unified view of amphiphilicpolymorphism".G. PORTE, USTL, Montpellier, France.

"High-resolution electron microscopyand its application to high-temperature superconductors".K. URBAN, Inst. fur Festkorperforschung,Forschungszentrum, Jiilich, Germany.

"Morphogenesis of unicellular algae".P. PELCE, Université de Provence - St. Jerome,Marseille, France.

"The human genome project (HGP)".V. NOWOTNY, Washington Univ. Schoolof Medicine, Missouri, USA.

"Liquid helium seen with neutrons".R. SCHERM, ILL, Grenoble, France.

"Future neutron sources: reactors or spallation ?"F. MEZEI, Hahn-Meitner Institut/BENSC, Berlin, Germany.

"Scars and isospectra: experiments in quantum chaosand mathematics".S. SRIDHAR, Northeastern University, Boston, USA.

"Hydrodynamics of quasicrystals".P. KALUGIN, Landau Institute, Moscow, Russia.

"Recent applications of muon-spin-resonance-spectroscopy to the study of magnetic propertiesof heavy fermion compounds".A. SCHENCK, ETH Zurich and Paul Scherrer Institute,Zurich, Switzerland.

"Fluctuations in the C60 fullerene: aspectsof rotational and translational fluidity".N. ASHCROFT, Cornell University, Ithaca, NY, USA.

"The onset of superfluidity in thin 4He filmsadsorbed on graphite".P. CROWELL, Cornell University, Ithaca, NY, USA.

"High pressure effects on 1-D transition metalchalcogenides, fulJerenes and high-temperaturesuperconductors".M. NUNEZ-REGUEIRO, CRTBT, CNRS,Grenoble, France.

WO R К S HO PS

Workshops organized orsponsored by the ILL in 1993

Braunschweig, Germany, May 10-11,1993.Workshop on Focusing Crystal Optics.

Organizers: MAGERL A., WAGNER V.

La Grande-Motte, France, May 17-19,1993.Journées de la Diffusion Neutronique

Organizers: CHIEUX P., FRIES E.

Grenoble (ILL), France, January 21-23,1993.International Workshop on the Use of Neutrons

and X-rays in the Study of Magnetism.Organizers: BROWN P.J., LANDER G.H., MARTINEZ Jv

STIRLING W.G., VETTIER C.

Grenoble (ILL), France, January 29,1993.Colloquium in memory of Walter Mampe.

Organizers: PENDLEBURY M., BOERNER H.

Grenoble (ILL), France, March 22-24,1993.International Workshop of the Institut Laue-Langevin

(ILL) and the Institut fuer Festkoerperforschung (IFF)der KFA Juelich on Dynamics of Disordered Materials II.Organizers: PETRY W., RICHTER D., DIANOUX A.J.

Grenoble (ILL), France, June 2-4,1993.Réunion Annuelle du Groupe Français d'Etude

des Quasicristaux. (Livre de Résumés 1 - 2)Organizer: JANOT C.

Grenoble, France, June 21-23,1993.Workshop on Progress in Gaseous Microstrip

Proportional Chambers.Organizer: GELTENBORT P.

Stockholm, Sweden, May 13-17,1993.Euroconference on Neutrons in Surface Science

and at Interfaces.Organizers: BERMEJO F.J., COSTA M.M.R.R.,DAHLBORG U., FONTANA M., GAMARI-SEALE H.,SCHERM R., LOVESEY S.W., DAHLBORG M.

Book PublishedBARUCHEL J., HODEAU J.L., LEHMANN M.,REGNARD J.R., SCHLENKER C. [Editors]Neutron and Synchrotron Radiation for Condensed MatterStudies. Volume 1. Theory, Instruments and Methods.(HERCULES: Higher European Course for Usersof Large Experimental Systems)(Springer Verlag, Berlin/Les Editions de Physique,Paris, 1993) ISBN 286883-185-0.

Conference ProceedingsPublished as Booksor Journal IssuesProceedings of the International Workshop on Dynamicsof Disordered Materials II.DIANOUX A.J., PETRY W., RICHTER D. [Editors]PHYSICA A 201 n° 1-3 (1993).

Proceedings of the ILL/ESRF Workshop on Methods in theDetermination of Partial Structure Factors of DisorderedMatter by Neutron and Anomalous X-ray Diffraction.SUCK J.B., RAOUX D., CHIEUX P., RIEKEL C. [Editors](World Scientific Publishing, Singapore, 1993)ISBN 981-02-1463-4.

Proceedings of the 7th Conference of the Liquids Sectionfor the European Physical Society on "Neutron Scatteringfrom Liquids".TEIXEIRA J., WANDERLINGH F., GIORDANO R.,DIANOUX A.J., BARNES A.J. [Editors]Journal of Molecular Structure 296, n°3 (1993).

Proceedings of the Workshop on the Use of Neutronsand X-rays in the Study of Magnetism.LANDER G.H., STIRLING W.G. [Editors]PHYSICA В Volume 192 , № 1-2 (1993).

THESES

Theses

in theed

itors]

BOUDARD M.Structure et propriétés dynamiques de la phase

icosaédrique AlPdMn.Thèse, Institut National Polytechnique de Grenoble,

Grenoble le 30 mars 1993.

EDER K.J.Das Superpendel - Ein neues System zur

Schwingungsisolierung fuer die Neutronenoptik.Inaugurât Dissertation, Leopold-Franzens-Universitaet

Innsbruck, Mai 1993.

GUTSMIEDL E.Erzeugung und Aufwaertsstreuung von ultrakalten

Neutronen in superfluessigem Hélium.Dissertation, Technische Universitat Munchen, 1993.

LAUTENSCHLAEGER G.Untersuchung der magnetischen Phasenuebergaenge

des Manganwolframats, MnWO4.Inaugurât Dissertation, Technische Hochschule

Darmstadt, 1993.

NOELDEKE C.Anordnung und Anregungen des Ammoniaks

in Ytterbiumliexaammin.Inaugurât Dissertation, Christian-Albrechts-Universitaet,

Kiel, 1993.

SCHMIDB.Inelastische magnetische Neutronenstreuung an den

quasi-eindimensionalen SingulettgrundzustandssystemenCsFeCl3 und CsFeBrç unter dem Einfluss eines aeusserenMagnetfeldes.

Inaugurât Dissertation, Universitaet Regensburg, 1993.

STUHR U.NeutronenspektrokopischeUntersuchungen

der Diffusion und der optischen Schwingungsmodenvon Wasserstoff in Metall-Wasserstoff-Systemen.

Dissertation, Technische Hochschule Darmstadt, 1993.

TORRELLES ALBAREDA J.Estudio de la relajacion estructural inducida

termicamente en aleaciones vitreas del sistema Ge-Semediante diffraccion de neutrones.

Memoria para optar al grado de Doctor en CienciasFisicas Universitat Autonoma de Barcelona, Febrero 1993.

WEBER M.Untersuchungen zur Vibrationsdaempfung an den

hochaufloesenden Gammaspektrometern GAMS 2/3 undGAMS 4 am ILL Grenoble. Kemspektroskopie an | 7 7 Т тund 177Lu.

Inaugurât Dissertation, Technische UniversitaetMuenchen, 1993.

ioning

CONFERENCE CONTRIBUTIONS

Conference ContributionsABINGDON, UK: ICANS-XII International

Collaboration on Advanced Neutron Sources -

1993/05/24-28

ANDERSON I., BOENI P., BUFFAT P., ELSENHAUS O.,

FRIEDLI H.P., GRIMMER H., HAUERT R., LEIFER K.,

MENELLE A., PENFOLD J., SOECHTIG J.

Recent progress in supermirrors at PSI. (Contributed paper)

ALICANTE, Spain: 2nd International Discussion

Meeting on Relaxations in Complex Systems -

1993/06/28-07/08

DIANOUX A.J., SAUVAJOL J.L., SMITH J.,

KNELLER G.R. Dynamics of cis- and trans-polyacetylene:

a combined inelastic neutron scattering and computer

simulation analysis. (Invited talk)

FRICK В., RICHTER D., ZORN R., FETTERS LJ. The

fast relaxation process near the glass transition in amorphous

polymers with different microstructure. (Contributed paper)

ANTIBES/JUAN-LES-PINS, France: 9th International

Colloquium on Plasma Processes - 1993/06/6-11

ANDERSON I., ELSENHAUS O., BOENI P., BUFFAT P.,

FRIEDLI H.P., GRIMMER H., HAUERT R., LEIFER K.,

SOECHTIG J. Artificial multilayer supermirrors for

neutron optics. (Contributed paper)

ASCONA, Switzerland: 2nd International Conference

on Magnetoelectric Interaction Phenomena in Crystals

(MEIPIC - 2) -1993/09/13-18

MCINTVRE G.J., VISSER D., COLDWELL T.R.,GRAF H., WEISS L., ZEISKE TH., PLUMER M.L.Magnetic ordering in the stacked triangular antiferromagnetСзМпВгз in the presence of an electric field. (Talk)

BEIDAIHE, China: Neutron Scattering Satellite

Meeting, NSS-93 -1993/08/17-19

CHATTOPADHYAY T. Modulated magnetic phases.(Invited talk)

KULDA J., LUKAS P., MIKULA P., VRANA M.High-resolution neutron diffraction study of internalstresses. (Poster)

KULDA J., STRAUCH D., ISHII Y. Experimental studyof inelastic structure factors in silicon. (Poster)

MCINTYRE G.J. Geometrical aspects of single-crystaldiffractometry with position-sensitive detectors. (Poster)

MCINTYRE G.J., PTASIEWICZ-BAK H. Phasesof magnetic structure factors of non-centrosymmetricmagnetised crystals by polarised-neutron diffraction. (Poster)

MIKULA P., KULDA J., L UKAS P., VRANA M.,WAGNER V., SCHERM R. Recent developments of theneutron monochromators based on bent perfect crystals.(Invited talk)

MIKULA P., LUKAS P., KULDA J., STRUNZ P.,SAROUN J., VRANA M., WAGNER V., ALEFELD B.Applications of curved crystals in many-crystal settings.(Poster)

BEIJING, China: XVIth International Congressof Crystallography -1993/08/21-29

BAUMBACH G.T., GAILHANOU M., MARTI U.,SILVA P., BESSIERE M., REINHART F.K., ILEGEMS M.Characterization of quantum well wires and surface gratingsby X-ray diffraction reciprocal space mapping.

CHATTOPADHYAY T., BROWN P.J. Suddendisappearance of three-dimensional magnetic orderingin Gd2CuO4. (Poster)

LEHMANN M.S. Protein diffraction around the sulfurK-absorption edge using 5 A X-rays from a storage ring.(Talk)

LEHMANN M.S., CIPRIANI F., DAUVERGNE F.,GABRIEL A., WILKINSON C. An image plate detectorfor quasi-Laue neutron diffractometry. (Poster)

LEHMANN M.S., WILKINSON C., GABRIEL A.,ALLIBON J., DAUVERGNE F. Position sensitivephotomultiplier tube neutron detector. (Poster)

MCINTYRE G.J. Empirical and calculated thermal-diffuse-scattering corrections for single-crystal diffractiondata collected with a two-dimensional position-sensitivedetector. (Poster)

MCINTYRE G.J., OLOVSSON I., PTASIEWICZ-BAK H.Chemical bonding and temperature effects in the chargeand spin densities of NiSO4 6 H 2 O and NiSO4 7 H 2 O. (Poster)

REEHUIS M., OULADDIAF В., VOMHOF T.,JEITSCHKO W. Magnetic order in the phosphidesHo 2 Fe| 2 P 7 , Nd 2 Co ) 2 P 7 and Ho 2 Co l 2 P 7 . (Talk)

BEIJING, China: XVIth International Congressof Crystallography. Synchrotron Radiation SatelliteMeeting -1993/08/31-09/03

LEHMANN M.S. Protein crystallographic measurementon the Troika undulator beam line of the ESRF. (Talk)

BENEDIKTBEUREN, Germany: BMFT VerbundtreffenNeutronen -1993/10/18-20

DORNER B. Magnetische Anregungen in den quasiI-D Systemen CsFeCI3 und CsFeBr, im Magnetfeld parallelund senkrecht zur Kettenrichtung. (Talk)

LISS K.D., MAGERL A., SPRINGER T.Beugungseigenschaften von Si|. xGe x Gradientenkristallen.(Poster)

MAGERL A., ZULEHNER W. OptimierteSauerstotïpraezipitation in Silizium: ein Beitrag derNeutronenstreuung zum Gigabit Bauelement. (Talk)

MAY R.P. D22, ein neues Instrument fuerNeutronenkleinwinkelstreuung am ILL. (Poster)

RITTER C., MONDAL S., CYWINSKI R..KILCOYNE S.H., RAINFORD B.D. A study of thetransition between intrinsic and induced Mn momentin the system Dy|.xYxMn2. (Poster)

STOELKEN S., BARTSCH E., SILLESCU H.,LINDNER P., ANTONIETTI M. KugelffoermigePolymermikronetzwerke - neuartige Materialien alsBindeglied zwischen Polymeren und Kolloiden. (Poster)

BRAUNSCHWEIG, Germany: Workshop on FocusingBragg Optics -1993/05/10-11

DORNER B. Comparison of gradient and mosaic crystalsby means of k-distributions in reciprocal space. (Talk)

KULDA J.. WAGNER V., MIKULA P., SAROUN J.Comparative tests of neutron monochromators usingelastically bent silicon and mosaic crystals. (Talk)

LISS K.D., MAGERL A. Can a gradient crystal competewith a mosaic crystal as a monochromator in neutron-or X-ray diffraction? (Talk)

MAGERL A., LISS K.D., DOLL C., MADAR R.,STEICHELE E. Will gradient crystals become availablefor neutron diffraction? (Contributed paper)

MIKULA P., KULDA J., LUKAS P., VRANA M.,WAGNER V., SCHERM R. Bent perfect crystalsin asymmetric diffraction geometry in neutron scatteringexperiments. (Talk)

MUTKA H. Coupled time and space focusingfor time-of-flight inelastic scattering. (Talk)

BRISTOL, UK: Vllth ECIS Conference -1993/09TERECH P. Surfactant aggregation in organic solvents:

physical gels and living polymers. (Poster)

BUDAPEST, Hungary: Workshop on the InternationalUse of Centres of Excellence and Joint Projects -1993/03/26-27

HEIDEMANN A. The ILL: An international neutronresearch center. (Poster)

CARGESE, France: NATO-ARW on Hydrogen BondNetworks -1993/08/16-22

DIANOUX A.J., HARRIS K.D.M., GUILLAUME F.Molecular motions in urea inclusion compounds.(Contributed paper)

CARRY-LE-ROUET, France: International Workshopon Electron Crystals - 1993/06/02-04

CURRAT R., LORENZO-DIAZ J.E. Neutron study ofphase transitions and low-frequency excitations in (MSe4)nIcompounds. (Invited talk)

COMO, Italy: NATO Advanced Study Institute"Modern Aspects of Small-Angle Scattering" -1993/05/12-22

LINDNER P. Polymers in solution. Flow techniques.(Invited talk).

MAY R.P. Small-angle neutron scattering of biologicalmacromolecular complexes consisting of proteins andnucleic acids. (Poster & Talk)

DRESDEN, Germany: Workshop on High-ResolutionSpectroscopy of Fission Fragments, Neutrons and y-Rays -1993/03

GELTENBORT P., MUELLER A., GOENNENWEIN F.,KAUFMANN J., PETROV G., DUERING I.. MAERTENH., RUBEN A., OED A. Cold fission studies usinga double-ionization chamber. (Contributed paper)

DUBNA, Russia: 3rd International Conference onSurface X-ray and Neutron Scattering -1993/06/24-29

BAUMBACH G.T., HOLY V. Umweganregung excitedby specular internal reflection and strong asymmetric X-raydiffraction.

BAUMBACH G.T., HOLY V., PIETSCH U.,GAILHANOU M. The influence of specular interfacereflection on grazing incidence diffraction and diffusescattering from superlattices.

SCHAERPF O. Surfaces and interfaces and their rolein supermirrors. (Invited talk)

EUGENE, USA: 20th International Conferenceon Low Temperature Physics -1993/08/04-11

MARTINEZ J.L., GARCIA-MATRES E..GARCIA-MUNOZ J.L.. RODRIGUEZ J.Magnetic properties of RiBaNiOs oxides. (Poster)

FLORENCE, Italy: 2nd Liquid Matter Conference -1993/09/18-22

SUCK J.-B., CHIEUX P., DUPUY-PHILON J..JALJ.-F..MORKELC.

Collective atomic dynamics in mixtures of liquid metalsand molten salts. (Contributed paper)

FRIBOURG, Switzerland: 8th International Symposiumon Capture Gamma-Ray Spectroscopy and RelatedTopics -1993/09/20-24

BOERNER H.G., PENDLEBURY J.M. Newdevelopments for the nuclear and fundamental physicsfacilities at the high flux reactor of the ILL Grenoble.(Invited talk)

onays-

DRISS1 S., DÉLÈZE M., GARRETT P.E., JOLIE J.,KERN J., MANNANAL S.J., TERCIER P.A., VORLET J.P.,WARR N., MOUZE G., YTHIER CH., BOERNER H.G.,JUDGE S., SCHRECKENBACH K., WILLIAMS A.Complete level structure of ' l2Cd and the SU(5) dynamicalsymmetry. (Invited talk & Contributed paper)

JUNGCLAUS A. The gamma-ray induced Doppler(GRID) broadening method: a status report. (Invited talk)

GAITHERSBURG, USA: The Eighth InternationalMeeting on Ferroelectricity -1993/08/08-13

KAMBA S., PETZELT J., ZELEZNY V., SMUTNY F.,DVORAK V., HLINKA J., QUILICHINI M., VOLKOV A.A.,GORSHUNOV B.P., KOZLOV G.V., CURRAT R.,LEGRAND J.F. Dynamical studies of fully deuteratedBCCD. (Contributed paper)

GARCHY, France: Rhéophysique des SuspensionsColloïdales -1993/12/15-17

TERECH P. Polymères vivants en milieu organique,exemple d'un complexe organométallique dans le cyclohexane.

GIF-SUR-YVETTE, France: Formation JeunesChercheurs "Frustration Géométrique en MatièreCondensée" -1993/12

CHARVOLIN J. Films d'amphiphiles. (Invited talk)

GLASGOW, Scotland: IXth International Conférenceof Virology -1993/08/08-13

TIMMINS P. A. The architecture of tomato bushy stuntvirus: Distribution of RNA and protein. (Contributed paper)

TIMMINS P.A. A decapsidation mechanism for turnipyellow mosaic virus. (Poster)

GRENOBLE, France: International Workshop on theUse of Neutrons and X-rays in the Study of Magnetism -1993/01/21-23

KULDA J. On the cross-section of the thermal neutroncoherent inelastic scattering. (Poster)

MCINTYRE G.J., PTASIEWICZ-BAK H., OLOVSSON I.Chemical bonding and covalency in NiSO4.6H2Oby measurement of charge and spin densities. (Poster)

OULADDIAF В., BALLOU R., LEKIEVRE-BERNA E.Magnetic phase diagram of TbMn^ (Poster)

RITTER C., CYWINSKI R., KILCOYNE S.H.,MONDAL S., RAINFORD B.D. Volume anomalies andthermal expansion in the system Dy(.xYxMn2. (Poster)

SCH AERPF O. Use of a multidetector in neutronpolarization analysis of magnetic scattering. (Poster)

SCHAERPF O. Absolute cross-section determinationof magnetic scattering from a La2CuO4 single crystal aboveTN . (Poster)

GRENOBLE, France: HERCULES Course -1993/02/14-04/02

LEHMANN M.S. Neutron crystallographyof biological molecules. (Invited talk)

TIMMINS P.A. Virus structure. (Invited talk)

GRENOBLE, France: Workshop on"Dynamics in Disordered Materials II" - 1993/03/22-24

BUCHENAU U., LINDER K., FRICK B. Debye-Wallerfactors in amorphous polymers. (Poster & Contributed paper)

DUVAL E., ACHIBAT T., BOUKENTER A., FRICK В.,GARCIA N., SERUGHETTI J. Comparison between lightand neutron inelastic scatterings. The frequency linearbehaviour of the light-vibration coupling coefficient.(Contributed paper)

FERRAND M. Thermal motions and functionof bacteriorhodopsin in purple membranes: effectsof temperature and hydration studied by neutron scattering.(Poster)

FERRAND M., DIANOUX A.J., PETRY W., ZACCAÏ G.Dynamical transition of bacteriorhodopsin in purplemembranes revealed by neutron scattering: a relation betweenstructure, dynamics and function. (Contributed paper)

FRICK В., RICHTER D., TREVINO S. Inelastic fastrelaxation in a weakly fragile polymer glass near T g .(Contributed paper)

ZORN R., RICHTER D., FRICK В., FARAGO B.Neutron scattering experiments on the glass transitionof polymers. (Invited talk & Contributed paper)

GRENOBLE, France: IAEA Interregional TrainingCourse on Nuclear Methods in Materials Research -1993/05/10-21

ANDERSON I. Multilayer design and productionfor neutron optics. (Talk)

CONVERT P. Thermal neutron detection. (Talk)

HEW AT A.W. High T c superconductors studiedby neutron powder diffraction. (Talk)

KEARLEY G. Molecular spectroscopy and catalysis.(Talk)

LINDNER P. Polymers in solution. Flow techniques.(Talk)

PANNETIER J. Studying chemical reactions by neutronpowder diffraction. (Talk)

RITTER C. Materials research on DIB. (Talk)

GRENOBLE, France: BEST, INPG, ENSPG SummerCourse "Neutrons and Synchrotron Radiation" -1993/09/14-24

DORNER B. Inelastic neutron scattering. (Invited talk)

TIMMINS P.A. Neutrons in biology. (Invited talk)

HELSINKI, Finland: Nordic Structural ChemistryMeeting-1993/01/11-13

MCINTYRE G.J., OLOVSSON I., PTASIEWICZ-BAK H. Spin and charge density in NiSO4.6H2O. Bondingdeformation and superposition effects. (Poster)

JUELICH, Germany: Neutron Scattering Seminar -1993/10/11-12

TRAMPENAU J., DUBOS O., HENNION В., PETRY W.Strongly anharmonic phonons in monoatomic bcc phases.(Invited talk)

KOCHI, Japan: Meeting of the Japanese PhysicalSociety Section on Elementary Particles -1993/10/04-06

PENDLEBURY J.M. Electric dipole momentsand CP violation. (Invited talk)

LA GRANDE-MOTTE, France: Secondes Journéesde la Diffusion Neutronique -1993/05/17-19

BALLOU R., DEPORTES J., OULADDIAF B.Effets de substitutions de Tb et Al sur l'hélimagnétismeà longue période dans le composé YMn2. (Poster)

BALLOU R., DEPORTES T., OULADDIAF B.Dimorphisme structural, instabilité magnétique et frustrationtopologique dans la série (Dy|_xLax)Mn2. (Poster)

CURRAT R. Etude par diffusion de neutronsdes transitions de phase dans les composés quasi-unidimensionnels (TaSe4)2I et (NbSe4)3I. (Poster)

DIANOUX A.J., KNELLER G.R., SAUVAJOL J.L.,SMITH J.C. Densité d'états vibrationnels du polyacétylène:simulations de dynamique moléculaire et comparaisonavec les résultats de diffusion des neutrons. (Poster)

MUTKA H. Diffusion Brillouin aux neutrons. Instrumentinélastique aux petits angles. (Poster)

MUTKA H., ECCLESTON R., MOLINIE P., PAYEN C.Effet de la température sur la dynamique de spinsde la chaîne antiferromagnétique de Heisenberg S=l :étude par la diffusion inélastique des neutronsde AgVP2S6. (Poster)

LONDON, UK: Third London Conferenceon Position-Sensitive Detectors -1993/09/6-10

GELTENBORT P., OED A. MicroStrip gas chambersat the Institute Laue-Langevin. (Talk)

LOUVAIN-LA-NEUVE, Belgium: Workshop onSymmetries in Semi-Ieptonic and Leptonic WeakInteractions -1993/06/4-7

LAST J. Cold, ultracold and polarised neutrons.(Invited talk)

PENDLEBURY J.M. Improving the neutron electricdipole moment measurements. (Invited talk)

LUNTEREN, Holland: European Research Conferenceon Dynamical Properties of Solids - 1993/09/26-30

CURRAT R. Neutron study of phase transitionsand low-frequency excitations in modulated crystals.(Invited talk)

SUCK J.-B. Collective excitations in topologicallydisordered systems studied by neutron inelastic scattering.(Invited talk)

MAINZ, Germany: Spring Meeting of the GermanPhysical Society, Section Hadrons and Nuclei -1993/03/21-26

ABELE H., HELM G., KANIA U., SCHMIDT C.,LASTJ., DUBBERSD.Verlustfreie Messung von 35S und 63Ni fi-Spektren,und der Ursprung der 17 keV Neutrino-Signale. (Talk)

FIONI G., HESSE M., FAUST H. Eine neuelonisationskammer fuer das erweiterte MassenspektrometerLOHENGRIN am ILL Grenoble. (Poster)

GELTENBORT P, OED A. Features of micro stripproportional counters (group report). (Talk)

MINNEAPOLIS, USA: 38th Annual Conference onMagnetism and Magnetic Materials -1993/11/15-18

BRAMWELL S.T. Order by disorder in an anisotropicpyrochlore antiferromagnet. (Talk)

BRAMWELL S.T. Weak ferromagnetismin a Kagome lattice antiferromagnet. (Talk)

CHATTOPADHYAY T., BROWN P.J., ROESSLI B.Disappearance of three-dimensional magnetic ordering inGd2CuO4. (Talk)

CHATTOPADHYAY T., ROSOV N.. LYNN J.W.,KAESTNER J., WASSERMANN E.F., BACH H.Temperature dependence of the magnetic excitations inordered and disordered Рез?!. (Talk)

ISNARD O., MIRAGLIA S., GUILLOT M.,FRUCHART D. High field magnetization measurements ofSm 2Fe| 7, Sm 2Fe I 7N 3, Sm 2 Fe| 7 D 5 and Pr2Fe,7, Pr2Fe,7N3.'Invited talk)

MITO, Japan: 5th International Symposiumon Advanced Nuclear Energy Research -1993/03

DORNER B. Inelastic neutron scatteringand polarized neutrons. (Panel contribution)

KULDA J., STRAUCH D., ISHII Y. Refinementof phonon eigenvector phases from intensities of neutroninelastic scattering in Si. (Contributed paper)

MONTE VERITA, Switzerland: 2nd InternationalConference on Magnetoelectric Interaction Phenomenain Crystals (MEIPIC - 2) -1993/09/13-18

MCINTYRE G.J., VISSER D., COLDWELL T.R.,GRAF H., WEISS L., ZEISKE T., PLUMER M.L. Magneticordering in the stacked triangular antiferromagnet CsMnBr3in the presence of an electric field. (Talk)

MONTERREY, USA: 20th RERC -1993/08MARTINEZ J.L., SAEZ PUCHO R., HERNANDEZ J.,

RODRIGUEZ;., GARCIA MATRES E. Magneticproperties of novel R7BaCoO.;.

MONTPELLIER, France: Journée de BiochimieStructurale -1993/12/02

TIMMINS P.A. Etudes structurales de macromoléculesbiologiques par diffusion des neutrons. (Invited talk)

NATHIAGALI, Pakistan: Seventeenth Internationa)Workshop on Condensed Matter Theories -1993/06/18-24

CLEMENTS B.E. Dynamic excitations in Bose liquidfilms. (Invited talk)

NEW LONDON, USA: Gordon Conference on X-rayPhysics -1993/08/09-13

LEHMANN M.S. Protein crystallography with softX-ray near the K-absorption edge of sulfur. (Talk)

OAK RIDGE, USA: Workshop on Fundamental Physicsat the Advanced Neutron Source -1993/11/09-10

BOERNER H.G. Precision gamma ray measurements:a review. (Invited talk)

PENDLEBURY J.M. Ultracold neutrons: a review.(Invited talk)

OKA YAMA, Japan: Meeting of the Japanese PhysicalSociety Section on Atoms and Molecules -1993/10/11-13

PENDLEBURY J.M. Fundamental physics withultracold neutrons. (Invited talk)

PREDEAL, Romania: NATO Advanced Study Institute"Frontier Topics in Nuclear Physics" -1993/08/24-09/04

JUNGCLAUS A., BOERNER H.G., JOLIE J., LIEBK.P., ULBIG S. Lifetime measurements with the gamma rayinduced doppler (GRID) broadening method. (Talk)

REGENSBURG, Germany: 13th General Conferenceof the Condensed Matter Division. European PhysicalSociety -1993/03/29-04/02

BAUMBACH G.T., PIETSCH U. Grazing incidenceX-ray diffaction and its interdependence on the specularX-ray reflectivity in the case of a semiconductor superlattice.(Abstract)

DIANOUX A.J., GUILLAUME F., EL BAGHDADI A.Dynamics of alkyl-type chains in crystals. (Contributed paper)

LISS K.D., MAGERL A., SPRINGER T., MADAR R.Fabrication and diffraction properties of Si|.xGex gradientcrystals. (Poster)

SCHAERPF O. A neutron multidetector with spinanalysis applied to measure absolute magnetic cross-sectionson high Tc materials. (Talk)

VOIT J. Charge-spin separation and the spectralproperties of Luttinger liquids. (Talk)

VOIT J., BARANOWSKI D., BUETTNER H.Electronic correlations and electron-libron couplingin polyaniline. (Abstract)

RIS0, Denmark: Users' Meeting -1993/01/08-09LINDNER P. Semidilute polymer solutions under shear.

(Poster)MAY R.P. D22, the new small-angle neutron scattering

facility at the ILL. (Poster)

ROSKILDE, Denmark: RITA Workshop -1993/08/28KULDA J. Elastically deformed versus mosaic

monochromators. (Talk)

ROUEN, France: Réunion Annuelle du Groupe DéfautsPonctuels -1993/06/24-25

RANDL O. Lacunes, phonons et diffusion atomiquedans des alliages intermétalliques. (Talk)

SACLAY, France: Conférence on Membrane Structure,Dynamics and Interactions via Neutron and X-rayScattering -1993/04

CHARVOLIN J. Membranes in chloroplastsand etioplasts. (Invited talk)

SACLAY, France: IXth Internationa] Conférenceon Small Angle Scattering -1993/04/27-30

LINDNER P. Semidilute polymer solutions under shear.(Poster)

MAY R.P. D22, the new small-angle neutron scatteringfacility at the ILL. (Poster)

MAY R.P. Geometrical optimisation of neutronsmall-angle scattering instruments. (Poster & Talk)

TIMMINS P.A. Small angle neutron scatteringfrom solutions and crystals of biological macromolecules.(Invited talk)

SACLAY-LLB, France: Réunion Thématique"Dynamique et Spectres de Phonons" -1993/03/11-12

SUCK J.-B. Generalized vibrational density of statesand total dynamic structure factor of icosahedral alloys.(Invited talk)

SAN DIEGO, USA: Fifth International Conferenceon the Crystallization of Biological Macromolecules -1993/08/08-13

TIMMINS P.A. The organisation of detergentsin solution and in crystals of membrane proteins.(Invited talk & Abstract)

SAN SEBASTIAN, Spain: QUENS'93 QuasielasticNeutron Scattering - 1993/09/27-28

DIANOUX A.J., EL BAGHDADI A., GUILLAUME F.,BOYSEN H., CODDENS G. Translational and rotationalmotions of n-alkane molecules within the channelsof urea inclusion compounds. (Contributed paper)

HEIDEMANN A. Directions in instrumentationfor quasielastic neutron scattering. (Invited talk)

MUTKA H. Energy-resolved small-angle thermalneutron scattering: a challenge for instrumentation. (Talk)

SAN SEBASTIAN, Spain: NATO Advanced ResearchWorkshop - "The Physics and Mathematical Physicsof the Hubbard Model" -1993/10/3-8

VOIT J. Charge-spin separation and the spectralproperties of Luttinger liquids. (Invited talk)

SANDBJERG CASTLE, Denmark: Nordic Schoolon the Application of X-ray Synchrotron Radiation -1993/06/25-07/03

LEHMANN M.S.Anomalous scattering in biology. (Talk)

LEHMANN M.S.The noble art of proposal writing. (Talk)

SEATTLE, USA: American Institute of PhysicsSpring Meeting -1993/03/22-26

BRAMWELL S.T. Critical propertiesof ultrathin films. (Talk)

BROWN P.J. Magnetic correlations in La2_xSrxNiO4.(Invited talk)

CHATTOPADHYAY T., SUMARLIN I.W.,LYNN J.W., BARILO S.N., ZHIGUNOV D.I.Magnetic excitons of Pr in Pr2CuO4. (Talk)

NEUMANN D.A., KAMITAKAHARA W.A.,FRICK B. Neutron scattering from vibrational modesin carbon solids. (Contributed paper)

NGAI K., FRICK В., TREVINO S.F., RICHTER D.Excitations in glassy polymers. (Contributed paper)

TRIESTE, Italy: Workshop on "The Liquid State ofMatter: Opportunities from New Radiation Sources" -1993/07

CHIEUX P., DAMAY P. Accuracy in neutron scatteringdetermination of the structure of disordered materials.(Invited talk)

CHIEUX P., DAMAY P. Is neutron small anglescattering an appropriate tool for the study of criticality ?(Invited talk)

TROIS-RIVIERES, QUEBEC, Canada: SixthInternational Conference on Organized Molecular Films -1993/07/04-09

LEGRAND J.F. X-ray grazing incidence studiesof the 2-D crystallization of monolayers of 1-alcoholsat the air-water interface. (Poster)

ULM, Germany: 28th Europhysics Conference on"Transitions in Oligomer and Polymer Systems" -1993/09/27-10/1

FRICK В., BUCHENAU U. Boson peak and fastrelaxation process near the glass transition in polystyrene.(Contributed paper)

VELDHOVEN, Holland: Europhysics IndustrialWorkshop EIW-9 - "Nanometer-scale Methods in X-rayTechnology" -1993/10/11-13

BAUMBACH G.T., GA1LHANOU M. X-ray diffractionfrom simple and epitaxial multilayered surface gratings.

BAUMBACH G.T., HOLY V. X-ray reflection fromrough periodical multilayers.

VILLEURBANNE, France: Colloque S.F.M.E. -1993/04CHEYNET M.C., SOLAS D., ANTONIADIS A.,

BERRUYER J., FILHOL A. Microanalyse des ségrégrationsen soluté dans les PFZ formés aux joints de graind'un alliage AI-Zn-Mg. (Contributed paper)

WARSAW, Poland: Polish Academy of Sciences Courseon Structural Biology -1993/01/21-24

TIMMINS P.A. Neutron scattering for the studyof biological macromolecules. (Invited talk)

TIMMINS P.A. Virus structure. (Invited talk)

SHEFFIELD, UK: UK Neutron Beam Users Meeting •1993/09/01-02

TIMMINS P.A. Neutrons in biology. (Invited talk)

STRASBOURG, France: E-MRS 1993 Spring Meeting -1993/05/4-7

BAUMBACH G.T., GAILHANOU M., FISCHER H.,MARTI U., SILVA P.C., REINHART F.K., ILEGEMS M.X-ray diffraction reciprocal space mapping of III-V gratings.

WINDSOR, UK: Conference on Quantum MolecularTunneling in Solids -1993/07/12-15

HEIDEMANN A. New methods in neutronspectroscopy. (Invited talk)

ZUOZ, Switzerland: Summerschool on NeutronScattering -1993/08/15-21

DORNER B. Structural excitations. (Invited talk)TIMMINS P.A. Neutron scattering in biology.

(Invited talk)

159 l&o

PUBLICATIONS - ILL-REPORTS

Publications -ILL-Reports 1993

This list groups publications received during 1993 resultingfrom the research at the ILL.ILL-Reports are listed first. They are followed by the listof publications in journals, conference proceedings, bookswith ILL authors and co-authors and by publications relatedto experimental work performed by visiting scientists at theILL but without ILL co-authors.

ILL-Reports(Code number I to 9)

93CO01GCOOK J.C. Monte Carlo simulation of the energy resolutionfunction of the backscattering spectrometer INIO.ILL-Report.

93PA02TPAPOULAR R.J., RESSOUCHE E., TASSET F.Comparison on various computers and workstations: runtimenecessary to compute a crystallographic inverse Fouriertransform using maximum entropy.ILL-Report.

93MA03TMA YERHOFER U. User's manual: a short guideand introduction to the hp9000/710 of college III.ILL-Report.

93NE04TNESVIZHEVSKY V.V. Error assessment for neutronlifetime measurement with MAMBO-2.ILL-Report.

93PEOSTPENDLEBURY M., BOERNER H. Colloquium in memoryof Walter Mampe. Grenoble (ILL), France, January 29,1993.ILL-Report.

93GE06TGELTENBORT P. Workshop on Progress in GaseousMicrostrip Proportional Chambers. Grenoble (France),June 21-23 1993.ILL-Report.

93JA07TJANOT C. Réunion annuelle du Groupe Français d'Etudedes Quasicristaux. Grenoble (France), 2-4 Juin 1993.(Livre de résumés 1 - 2)ILL-Report.

93JA08TJANOT C. Conférence Quasicristaux. Commande de travauxsur mémoire MS/SC n°92-1552/AOOO/DRET/DS/SR.Fiche de synthèse, Ministère de la Défense -Direction des Recherches Etudes et Techniques.ILL-Report.

93FA09TFAUST H., AGERON P., FOGELBERG В., JACOBSONL., PINSTON J.A., BENABED A., LIATARD E., PIAFECOLLABORATION. Principles on the implantationof a thermal ion source in the H9 beam tube of the ILL.Progress report.ILL-Report.

Papers published in Scientific periodicals,Books and Conference Proceedings:

1. With ILL authors & Co-authors(Code number 101 to 400).

93FE101FERNANDEZ-DIAZ M.T., MARTINEZ J.L.,RODRIGUEZ-CARVAJAL J., BEILLE J., MARTINEZ В.,OBRADORS X., ODIER P.Metamagnerism in single-crystal Pr2NiO4

Physical Review В 47, 5834-5840 (1993).

93JU102JUNGCLAUS A., BOERNER H.G., JOLIE J., ULBIG S.,CASTEN R.F., ZAMFIR N.V., BRENTANO P. V.,LIEB K.P. Absolute B(EI ) values in the shape transitionall 4 X - | 3 2 Sm isotopes.Physical Review С 47, 1020-1026 (1993).

93LA103LANGAN P., FORSYTH V.T., MAHENDRASINGAM A.,PIGRAM W.J., MASON S.A., FULLER W. A high angleneutron fibre diffraction study of the hydration of the Aconformation of the DNA double helix.Journal of Biomolecular Structure and Dynamics 10,489-503(1992).

93VE104VERGNAT M., HOUSSAINI S., MARCHAL G., MANGINP., VETTIER C. Hydrogen diffusion and densificationin amorphous silicon.Physical Review В 47, 7584-7587 (1993).

93МШ05MUTKA H., PA YEN C., MOLINIE P.One-dimensional Heisenberg antiferromagnet with spinS = 3/2. Experiments on AgCrP2S6.Europhysics Letters 21, 623-628 (1993).

93BE106BEAUFILS J.P. Structural study, by surface differentialdiffraction of neutrons, of the surface of a nickel powdercovered with deuterium.Surface Science 280, 197-207 (1993).

93RI107RICHTER D., FARAGO В., BUTERA R., FETTERS L.J.,HUANG J.S., EWEN B.On the origins of entanglement constraints.Macromolecules 26, 795-804 (1993).

93FA108FANJAT N.. LUCAZEAU G.Magnetic properties of Ре2Наз(РО4)з-1. Calculationof magnon dispersion curves in a complex structure.Journal of Physics and Chemistry of Solids 54, 1 87- 1 96(1993).

93DO109DOENNI A., FURRER A., FISCHER P., HAYDEN S.M.,HULLIGER F., SUZUKI T.Magnetic properties of the dense Kondo compound CeSestudied by neutron scattering.Journal of Physics: Condensed Matter 5, 1 1 19-1 132 (1993).

93GA110GARCIA-MATRES E., RODRIGUEZ-CARVAJAL J.,MARTINEZ J.L., SALINAS-SANCHEZ A.,SAEZ-PUCHE R. Magnetic structure of Ho2BaNiO5.Solid State Communications 85, 553-559 (1993).

93MU111MUTKA H., PA YEN C., MOLINIE P.Finite segments, "free spins" and random exchangein spin S=l quasi one-dimensional antiferromagnets.Solid State Communications 85, 597-599 (1993).

93BO112BOUDARD M., BOISSIEU M. DE, JANOT С., HEGER G.,BEELI С., NISSEN H.U., VINCENT H., AUDIER M.,DUBOIS J.M. Atomic structure of the Al-Pd-Mnicosahedral phase.Journal of Non-Crystalline Solids 153-154, 5-9 (1993).

93BO113BOISSIEU M. DE, BOUDARD M., MOUDDEN H.,QUILICHINI M., BELLISSENTR., HENNION В.,CURRAT R., GOLDMAN A., JANOT C.Dynamical properties of the AIPdMn icosahedral phase.Journal of Non-Crystalline Solids 153-154, 552-556 (1993).

93KL114KLEIN T., PARES G., SUCK J.B., FOURCAUDOT G.,CYROT-LACKMANN F. Atomic dynamics of icosahedral

a comparative study using inelastic neutron scattering.Journal of Non-Crystalline Solids 153-154, 562-567 (1993).

93SU115SUCK J.B.Generalized vibrational density of states of icosahedralAl7 |Pd,gMn, ( ).Journal of Non-Crystalline Solids 153-154, 573-577 (1993).

93CL116CLEMENTS B.E., KROTSCHECK E., LAUTER H.J.

Growth instability in helium films.Physical Review Letters 70, 1287-1290 (1993).

93FI117FITCH A.N., COCKCROFT J.K.The structure of solid carbon tetrafluoride.Zeitschrift fuer Kristallographie 203, 29-39 (1993).

93SC118SCHNEIDER M., LUTZ H.D., COCKCROFT J.K..Polymorphic und Pseudosyrnmetrie von LiiCoCbt.Zeitschrift fuer Kristallographie 203, 183-197 (1993).

93BE119BERTHOLD H.J., VONHOLDT E., WARTCHOW R.,VOGT T.

Neutron diffraction study of the orthorhombic low-temperature phase of N2D7I and x-ray investigationsof the tetragonal and orthorhombic phases of N2H7I.Zeitschrift fuer Kristallographie 203, 199-214 (1993).

93BA120BALDO CEOLIN M., BENETTI P., BOBISUT F., GIBIN D.,GUGLIELMI A., MATTIOLI F., MEZZETTO M.,PUGLIERIN G., SCONZA A.,VISENTIN L.Performance of the N-N scintillation counters triggerand TOP system.Il Nuovo Cimento 105A, 1679-1690(1993).

93FO121FORSYTH V.T., LANGAN P., MAHENDRASINGAM A.,FULLER W., MASON S.A.High-angle neutron fiber diffraction studies of DNA.Neutron News 3, n°4, 21-24 (1992).

93SA122SAUVAJOL J.L., DJURADO D., DIANOUX A.J.,FISCHER J.E., SCHERR E.M., MACDIARMID A.G.Polarized vibrational density of states of polyaniline fromincoherent neutron scattering: measurements of the phenyl-ring dynamics.Physical Review В 47,4959-4963 (1993).

93AS123ASMUSSEN В., PRESS W., PRAGER M., BLANK H.Rotational excitations in CH4/krypton mixtures.Journal of Chemical Physics 98, 158-163 (1993).

93PE124

PETKOV P.. ANDREJTSCHEFF W., ROBINSON S.J.,MAYERHOFER U., VON EGIDY T., BRANT S.,PAAR V., LOPAC V.Electromagnetic transition strengths in the transitional

doubly odd nucleus Au.Nuclear Physics A 554, 189-208 (1993).

93HO125

HOCK R., VOGT T., KULDA J., MURSIC Z., FUESS H.,MAGERL A.

Neutron backscattering on vibrating silicon crystals -experimental results on the neutron backscatteringspectrometer JN10.

Zeitschrift fuer Physik В 90, 143-153 (1993).

93ST126

STROKA В., SCHROEDER A., TRAPPMANN T.,LOEHNEYSEN H. V., LOEWENHAUPT M., SEVERING A.Crystal-field excitations in the heavy-fermion alloysCeCu6.xAux studied by specific heat and inelasticneutron scattering.Zeitschrift tuer Physik В 90, 155-160 (1993).

93SC127

SCHLFCHENMAIER R., SCHWEDA E.,STRAEHLE J., VOGT T.

Synthèse und Struktur von Z ^ O ^ F j , einer Verbindungmit fluorit-verwandter Ueberstruktur vom Vernier-typ.

Zeitschrift fuer Anorganische und Allgemeine Chemie 619,367-373(1993).

93SC128SCHAERPF O., CHATTOPADHYAY T., WEBER H.W.,HYUN O.B., FINNEMORE O.K.

Polarized neutron experiments on REBa2Cu3O7_5with polarization and time of flight energy analysis.

Physica Status Solidi (b) 175, 175-196(1993).

93BA129BARTSCH E., BERTAGNOLLI H., CHIEUX P.,DAVID A., SILLESCU H.

Temperature dependence of the static structure factorof ortho-terphenyl in the supercooled liquid regime closeto the glass transition.

Chemical Physics 169, 373-378 (1993).

93VO130VOITJ.

Charge-spin separation and the spectral propertiesof Luttinger liquids.

Physical Review В 47,6740-6743 (1993).

93РИ31PILSL H., HOFFMANN H., HOFMANN S., KALUS J.,KENCONO A.W., LINDNER P., ULBRICHT W.Shape investigation of mixed micelles by small angleneutron scattering.Journal of Physical Chemistry 97, 2745-2754 (1993).

93NO132NOZ1ERES P.Amplitude expansion for the Grinfeld instabilitydue to uniaxial stress at a solid surface.Journal de Physique 13,681 -686 ( 1993).

93FI133FISCHER P., KALDIS E., KARP1NSKI J., RUSJECK1 S.,JILEK E., TROUNOV V., HEW AT A.W.Neutron diffraction analysis of ^ C a and Ca substitutedsuperconductors YBa^C^Ojj with T c = 90 K.Physica С 205, 259-265 (1993).

93GA134GARCIA-MATRES E., MARTINEZ J.L., RODRIGUEZ-CAR VAJAL J., ALONSO J.A., SALINAS-SANCHEZ A.,SAEZ-PUCHE R. Structural characterization andpolymorphism of R2BaNiO5 (R = Nd, Gd, Dy, Y, Ho, Er,Tm, Yb) studied by neutron diffraction.Journal of Solid State Chemistry 103, 322-333 (1993).

93AR135ARBE A., ALEGRIA A., ALVAREZ F., COLMENERO J.,FRICK B. Dynamics of the a-relaxation in glass-formingpolymeric systems. Study by neutron scattering andrelaxation techniques.Progress in Colloid and Polymer Science 91, 24-27 (1993).

93BA136BASTIDE J., BOUE F., MENDES E., ZIELINSKI F.,BUZIER M., LARTIGUE C., OESER R., LINDNER P.Is the distribution of entanglements homogeneousin polymer melts ?Progress in Colloid and Polymer Science 91,105-108(1993).

93EW137EWEN В., RICHTER D., FARAGO В., MASCHKE U.The effect of microscopic spatial restrictionson the segmentai diffusion of dense polymer systems: theirobservation and analysis by neutron spin echo spectroscopy.Progress in Colloid and Polymer Science 91,121-123(1993).

93RI13SRICHTER D., EWEN В., FETTERS L.J., HUANG J.S.,FARAGO B. On the dynamics of dense polymer systems.Progress in Colloid and Polymer Science 91,130-134(1993).

93HE139HELLMANN G.P., HELLMANN E.H., RENNIE A.R.Chain fragmentation and fragment diffusion at the glasstransition.Progress in Colloid and Polymer Science 91,146-148(1993).

93OL140OLOVSSON I., PTASIEWICZ-BAK H., MCINTYRE G.J.Superposition and polarization effects on the electrondensity of lone pairs.Zeitschrift fuer Naturforschung A 48, 3-1 ! (1993).

93DA141DAY P., DELFS C.D.. FIGGIS B.N., REYNOLDS P.A..TASSET F.Polarized neutron diffraction from CsiKFe(CN)6.The orbital moment and its anisotropy.Molecular Physics 78, 769-780 (1993).

93MO142MORAL A. DEL, ARNAUDAS J.I., GEHRING P.M.,SALAMON MB., RITTER C, JOVEN E., CULLEN J.Magnetic first-order phase transition and crossoverassociated with random anisotropy in crystallineDyxY,.xAI2.Physical Review В 47, 7892-7896 (1993).

93WI143WILLIAMS J.H. Modeling the vibrational dynamicsof solid beiuene: hexafluorobenzene. The anatomyof a phase transition.Chemical Physics 172, 171-186(1993).

93VO144VOGT T., FITCH A.N., COCKCROFT J.K. A powderneutron diffraction investigation of the solid phases of IF7.Journal of Solid State Chemistry 103, 275-279 (1993).

93PA145PAIXAO J.A., LANDER G.H., TANG C.C., STIRLING W.G.,BLAISE A., BURLET P., BROWN P.J., VOGT O.Magnetization, neutron- and resonant x-ray diffractionstudies of U0 xsTho |SSb.Physical Review В 47, 8634-8645 (1993).

93LA146LANGEL W., PRAGER M., FLEGER H.W.,KNOEZINGER E., LAUTER H.J., BLANK H.,CARLILE C.J. Methane tunneling in disordered solidargon-nitrogen phases.Journal of Chemical Physics 98, 4838-4849 (1993).

93KE147KELLERSOHN T., DELAPLANE R.G., OLOVSSON I.,MCINTYRE G.J. The experimental electron density inmonoclinic cobalt sulfate hexahydrate, CoSO^oDiO. at 25K.Acta Crystallographica В 49, 179-192 (1993).

93PT148

PTASIEWICZ-BAK H., OLOVSSON I., MCINTYRE G.J.

Bonding deformation and superposition in the electron

density of tetragonal NiSO4.6H2O at 25 K.

Acla Crystallographica В 49, 192-201 (1993).

93HA149

HARRISON D.H., MAY R.P., MOORE P.B.

Measurement of the radii of gyration of ribosomalcomponents in situ by neutron scattering.

Journal of Applied Crystallography 26, 198-206 ( 1993).

93SC150

SCHAERPF O., CAPELLMANN H. The XYZ-differencemethod with polarized neutrons and the separationof coherent, spin incoherent, and magnetic scattering crosssections in a multidetector.

Physica Status Solidi (a) 135, 359-379 (1993).

93HI15I

HILFRICH K., KOELKER W., PETRY W., SCHAERPF O.,NEMBACH E. Growth of antiphase domains in ОО?

long-range ordered iron-rich iron-silicon alloys.Zeitschrift fuer Metallkunde 84, 255-258 (1993).

93CH1S2

CHAHID A., BERMEJO F.J., ENCISO E., GARCIA-HERNANDEZ M.. MARTINEZ J.L. Magnetic dynamicsin the disordered phases of condensed oxygen.Journal of Physics: Condensed Matter 5, 423-442 (1993).

93VO1S3

VOGT T., SCHMAHL W.W. The high-temperature phasetransition in perovskite.

Europhysics Letters 24, 281-285 (1993).

93ME154

MESOT J., ALLENSPACH P., STAUB U., FURRER A.,MUTKA H. Neutron spectroscopic evidence for clusterformation and percolative superconductivity in ErBaiCu3Ox.Physical Review Letters 70, 865-868 (1993).

93RI155

RITTER C., IBARRA M.R., IBBERSON R.M.

The low-temperature orthorhombic structure of YCu.

Journal of Physics: Condensed Matter 4, L39-L42 (1992).

93BR156

BRAMWELL ST., HOLDSWORTH P.C.W.

Magnetization and universal sub-critical behaviour

in two-dimensional XY magnets.

Journal of Physics: Condensed Matters, L53-L59 ( 1993).

P U B M C A T / O N S - ILL-REPORTS

93ТШ57TURRILLAS X., BARNES P , TARLING S.E.,JONES S.L., NORMAN C.J., RITTER C.Neutron thermodiffractometry and synchrotron energy-dispersive diffraction studies of zirconium hydroxidecalcination.Journal of Materials Sciences Letters 12, 223-226 (1993).

93DU158

DUPUY J.. JAL J.F., PREVEL В., AOUIZERAT-ELARBY A., CHIEUX P., DIANOUX A.J., LEGRAND J.F.

Vibrational dynamics and structural relaxation in aqueouselectrolyte solutions in the liquid, undercooled liquidand glassy states. "European Workshop on Glassesand Gels", January 29-31. 1992.

Journal de Physique IV, Colloque 2, 179-184 (1992).

93RO1S9

ROUSSELOTC, MERCIER R., MALUGANI J.P.,TACHEZ M., CHIEUX P. Modélisation de l'ordreà moyenne distance dans les verres surperconducteursioniques AgPO^-AgX par diffraction de neutrons."European Workshop on Glasses and Gels",January 29-31, 1992.Journal de Physique IV, Colloque 2, 219-222 (1992).

93RO160

ROUSSELOT С., TACHEZ M.. MAI .UGANI J.P.,MERCIER R., CHIEUX P. Structure primaire des verressuperconducteuis ioniques AgPO3-AgX par diffractiondes neutrons. "European Workshop on Glasses and Gels",January 29-31, 1992.Journal de Physique IV, Colloque 2, 211 -214 ( 1992).

93BO161

BOUQUIERE J.P., FINNEY J.L., LEHMANN Vi.S.,LINDLEY P.F., SAVAGE H.F.J. High-resolution neutronstudy of vitamin B, 2 coenzyme at 15 К: structure analysisand comparison with the structure at 279 K.Acta Crystallographica В 49,79-89 (1993).

93WA162

WAGEMANS C., D'HONDT P., BRISSOT R.

Determination of the 3 2S(n t h, a)2 9Si and 3 3S(n t h, oc)30Si

reaction cross-sections.

Journal of Physics G 19, supplement, 247-252 (1993).

93FE163

FERRAND M., ZACCAI G., NINA M., SMITH J.C.,ETCHEBEST C., ROUX B. Structure and dynamicsof bacteriorhodopsin. Comparison of simulationand experiment.FEBS Letters 327, 256-260 (1993).

93ME164MESOT J., ALLENSPACH P., STAUB U., FURRER A..MUTKA H., OSBORN R., TAYLOR A.D.Neutron spectroscopic studies of the crystal fieldin ErBa2Cu3Ox (6<x<7).

93PA165PAYER A., SCHOELLHORN R., RITTER C.,PAULUS W. Neutron diffraction study of the structureof chalcogen spinels Cu 1 + Y Cr 2 X 4 (X = Se, Te).Journal of Alloys and Compounds 191, 37-42 (1993).

93BO166BOERNER H.G., JOLIE J. Sub-picosecond lifetimemeasurements by gamma ray induced Doppler broadening.Journal of Physics G 19, 217-248 (1993).

93NE167NEEDHAM L.M., CUTRONI M., DIANOUX A.J.,ROSENBERG H.M. A study of the vibrational spectrumof amorphous and crystalline SeTe samples by inelasticneutron scattering.Journal of Physics: Condensed Matters, 637-646 (1993).

93TE168TERBURG B.P., VERKERK P., JERICHA E.,ZAWISKY M. Coherent scattering length measurementon krypton with neutron interferometry at a small reactor.Journal of Neutron Research 1, n"2, 37-42 (1993).

93TR169

TRAMPENAU J., PETRY W., HERZIG C.^emperature dependence of .ie lattice dynamicsof chromium.Physical Review В 47, 3132-3137 (1993).

93BA170BAROCCHI F., CHIEUX P., MAGbl R., REATTO L.,TAU M. Neutron diffraction study of liquid kryptonand the interatomic interaction.Physical Review Letters 70, 947-950 (1993).

93AB171

ABELE H., HELM G., KANIA U., SCHMIDT C., LAST J.,DUBBERS D. On the origin of the 17 KeV neutrino signaland a !oss-free measurement of the 3:>S p-spectrum.Physics Letters В 316. 26-31 (1993).

93DR172

DRUYTS S., WAGEMANS C , POMME S.,GELTENBORT P., TRAUTVETTER H.P.Measurement of the l4N(n t |p p)' 4C reaction cross-section.Journal of Physics G 9, supplement, 243-246 (1993).

93HO173HORSEWILL A.J., HEIDEMANN A., HAYASHI S.Hydrogen bond dynamics in dodecanoic acid studiedby QNS and NMR.Zeitschrift fuer Physik В 90, 319-324 (1993).

93BR174BRAMWELL ST., WILLIAMS J.H. Thermal expansion ofthe lowest-temperature phase of benzene:hexafluorobenzene.Journal of the Chemical Society Faraday Transactions 88,2721-2724(1992).

93MC175MCMAHON M.I., NELMES R.J., PILTZ R.O.,KUHS W.F., WRIGHT N.G. Neutron-diffraction studiesof the heavy-atom structure in H-ordering materials.Ferroelectrics 124, 351-354 (1991).

93UW176UWAHA M. Evolution of a train of interacting stepsin a surface diffusion field.Journal of Crystal Growth 128,92-96 (1993).

93UW177UWAHA M., SAITO Y. Fluctuation of stepsin a surface diffusion field.Journal of Crystal Growth 128, 87-91 (1993).

93GO178GOENNENWEIN F., BOERSIG В., NAST-LINKE U.,NEUMAIER S., MUTTERER M., THEOBALD J.P.,FAUST H., GELTENBORT P. Emission of clustersin nuclear fission.Institute of Physics Conference Series 132,453-458 (1993).

93BE179BERNSTEIN E., BLANCHIN M.G., RAVELLE-CHAPUIS R.,RODRIGUEZ-CARVAJALJ. Structural studiesof phase transformations in ultrafine zirconia powders.Journal of Materials Science 27, 6519-6524 (1992).

93SA180SAITO Y., UWAHA M., SEKI S. Dynamics and structure ofan aggregation growing from a diffusion field.In "Interactive Dynamics of Convection and Solidification"S.H. Davis et al. Eds.(Kluwer Academic Press, 1992) pp. 27-29.

93МСШMCEWEN K.A., STEIGENBERGER U., MARTINEZ J.L.Magnetic excitations and phase transitions in UPd3.Physica В 186-188, 670-674 ( 1993).

93GU182GUETHOFF F., PETRY W., STASSIS C, HEIMING A.,HENNION В., HERZIG C., TRAMPENAU J.Phonon dispersion of bcc La.Physical Review В 47, 2563-2572 (1993).

93LO183LORENZO J.E., CURRAT R., MONCEAU P., HENNION В.,LEVY F. Neutron investigation of optic-phonon branches inthe quasi-one-dimensional compound (TaSe4bI.Physical Review В 47, 10116-10121 (1993).

93HA184HARDER A., MICHAELSEN S., LIEB K.P.,WILLIAMS A.P. Thermal neutron capture y-rayspectroscopy of 5 9Ni and 6 1Ni.Zeitschrift fuer Physik A 345, 143-53 (1993).

93BO185BOUDARD M., BOISSIEU M. DE, JANOT С.Quasi-crystal structure: one drawback of Patterson analyses.Europhysics Letters 22, 181-186 (1993).

93BA186BAROCCH1 F., CHIEUX P., MAGLI R., REATTO L.,TAU M. Static structure of dense krypton and interatomicinteraction.Journal of Physics: Condensed Matter 5, 4299-4314 (1993).

93BE187

BENA I., MISBAH C., VALANCE A. Nonlinear evolutionof a terrace edge during step-flow growth.Physical Review В 47, 7408-7419 (1993).

93LE188

LEHMANN M.S., MUELLER H.H., STUHRMANN H.B.Protein single-crystal diffraction with 5 A synchrotronx-rays at the sulfur K-absorption edge.Acta Crystallographica D 49,308-310 (1993).

93BA189BASTIDE J., BOUE F., MENDES E., ZIELINSKI F.,BUZIER M., BEINERT G., OESER R., LARTIGUE C.Neutron scattering investigation of the deformationat molecular scales in polymer networks.Poly mer Net works 91, 119-145 (1992).

93PA190PASYUK V.V., LAUTER H.J., JOHNSON M.T.,DEN BROEDER F.J.A., JANSSEN E., BLAND J.A.C.,PETRENKO A.V., GAY J.M. Interface magnetisationin a single ultra-thin Pd/Co/Pd sandwich structure.Journal of Magnetism and Magnetic Materials 121,180-184(1993).

93BA191BATESON R.D., FORD G.W., BLAND J.A.C, LAUTERH.J., HEINRÏCH В., CELINSKI Z. Diffuse polarised neutronreflection studies of ultrathin bcc Fe(001 ) epitaxial films.Journal of Magnetism and Magnetic Materials 121,189-193 (1993).

nalyses.

93HO192HOPPE U., CHIEUX P., STACHEL D. Reverse MonteCarlo modelling of some metaphosphate glass structures.Zeitschrift fuer Kristallographie Supplement 7, 88 (1993).

93ST193STAUB U., MESOT J., ALLENSPACH P.. FURRER A.,MUTKA H. Crystal field, cluster formation and percolativesuperconductivity in ЕгВа2СизОх.Journal of Alloys and Compounds 195, 595-598 (1993).

93JA194JANOT C. The structure of quasicrystals.Journal of Non-Crystalline Solids 156-158, 852-864 (1993).

93FO195FORD G.W., O'CONNELL R.F. Relativisticform of radiation reaction.Physics Letters A 174, 182-184(1993).

93MA196MAERZ K., LINDNER P., URBAN G., KUGLER J.,BALLAUFF M., FISCHER E.W. Conformation and shapeof rigid-.vd polyesters substituted with flexible side chainsas revealed by small-angle neutron scattering.Acta Polymerica 44, 139-147 (1993).

93ST197STEYTLER D.C., ROBINSON B.H., EASTOE J., IBEL K.,DORE J.C., MCDONALD I. Effects of solidificationof the oil phase on the structure of colloidal dispersionsin cyclohexane.Langmuir 9, 903-911 (1993).

93ZA198ZARBAKHSH A., COWLAM N.. CONVERT P.,HIGHMORE R.J., SOMEKH R.E. Neutron diffractionstudy of a Ni-42.2 at % Zr alloy made by the multilayeramorphisation reaction and of Ni-42.2 at % Zr metallicalloy glass.Journal of Non-Crystalline Solids 156-158, 177-180(1993).

93FI199FIONI G., FAUST H.R., GROSS M., HESSE M.,ARMBRUSTER P., GOENNENWEIN F.,MUENZENBERG G. Reduction of energy dispersionon a parabola mass spectrometer.Nuclear Instruments and Methods in Physics Research A332, 175-180(1993).

93CH200CHEVRIER J., SUCK J.B., LASJAUNIAS J.C.Lattice instability in aluminum-silicon solid solutions.Journal of Non-Crystalline Solids 156-158,564-566 (1993).

93SU201SUCK J.B. Dynamical properties of stable icosahedral alloys.Journal of Non-Crystalline Solids 156-158,872-881 (1993).

93MA202MARET M., DUBOIS J.M., CHIEUX P.Neutron scattering study of quasicrystal-forming liquidalloys: Al 7 1 Pdi 9 M 1 0 (M = Mny(FeCr),.y).

Journal of Non-Crystalline Solids 156-158, 918-922 (1993).

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ROESSLI В., FISCHER P., ZOLLIKER M.,ALLENSPACH P., MESOT J., STAUB U., FURRER A.,KALDIS E., BUCHER В., KARPINSKI J., JILEK E.,MUTKA H. Crystal-field splitting and temperaturedependence of two-dimensional antiferromagnetismin the high-Tc compound DyBa2Cu4O8.Zeitschrift fuer Physik В 91, 149-153 (1993).

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93BA205BARANOWSKI D., BUETTNER Helmut, VOIT J.Breakdown of the spin-Peierls state in a one-dimensionalmodel for electron-libron coupling.Physical Review В 47, 15472-15475 (1993).

93WU206WUTTKE J., KIEBEL M., BARTSCH E., FUJARA F.,PETRY W., SILLESCU H. Relaxation and phonons inviscous and glassy orthoterphenyl by neutron scattering.Zeitschrift fuer Physik В 91, 357-365 (1993).

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JAYASOORIYA U.A., CANNON R.D., WHITE R.P.,STRIDE J.A., GRINTER R., KEARLEY G.J.Exchange interactions in trinuclear basic chromium (III)clusters: direct observation of the magnetic spectrum byinelastic neutron scattering.Journal of Chemical Physics 98,9303-9310 (1993).

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BLANK H., KEARLEY G.J. The effect of anionsubstitution in nickel hexammine salts.Journal de Physique IV C5, 345-349 (1991).

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PROFFEN T., NEDER R.B., FREY F., KEEN D.A.,ZEYEN C.M.E. Defect structure and diffuse scatteringof zirconia single crystals with 10 and 15 mol% CaO attemperatures up to 1750 K.Acta Crystallographica В 49,605-610 (1993).

93MI210MIEHE G., VOGT T., FUESS H., MUELLER U.A study of disorder in the SiO2 host lattice of dodecasil 1Husing synchrotron radiation.Acta Crystallographica В 49, 745-754 (1993).

93GI211GIAMARCHI T., VARMA C.M., RUCKENSTEIN A.E.,NOZIERES P. Singular low energy propertiesof an impurity model with finite range interactions.Physical Review Letters 70, 3967-3970 ( 1993).

93MU212MUTKA H. A dedicated instrument for thermal neutronBrillouin scattering - Design and simulation.Journal of Molecular Structure 296, 321-328 (1993).

93CR213CRETTEZ J.M., COQUET E., BOUILLOT J., LE ROY J.,PANNETIER J. Temperature dependence of the structureof 1Л|_хНх1Оз studied by high resolution neutron powderdiffraction between 10 and 380 K.Journal of Solid State Chemistry 105, 336-345 (1993).

93ST214STRAUCH D., DORNER B.Lattice dynamics of ct-quartz: /. Experiment.Journal of Physics: Condensed Matter 5, 6149-6154 (1993).

93SC215SCHOBER H., STRAUCH D., NUETZEL K., DORNER B.Lattice dynamics of cc-quartz: II. Theory.Journal of Physics: Condensed Matter 5, 6155-6164(1993).

93SC216SCHOBER H., STRAUCH D. Investigation of the LO-TOsplitting in complex binary crystals.Journal of Physics: Condensed Matter 5,6165-6182 (1993).

93CH217CHAHID A., BERMEJO F.J., CRIADO A., MARTINEZ J.L.,GARCIA-HERNANDEZ M.Spin dynamics in p-oxygen.Journal of Physics: Condensed Matter 5,6295-6312 ( 1993).

93BA218BAROCCHI R, CHIEUX P., MAGLI R.Precise experimental determination of the structureof noble gases: two- and many-body contributions.Journal of Physics: Condensed Matter 5, B49-B63 (1993).

93BE219BERMEJO F.J., СНАН1Г A., CRIADO A., GARCIA-HERNANDEZ M., MARTINEZ J.L., MOMPEAN F.J.Neutron inelastic scattering from molecular liquidsand glasses.Journal of Molecular Structure 296, 295-311 (1993).

93BE220BERMEJO F.J., MOMPEAN F.J., GARCIA-HERNANDEZ M.,MARTINEZ J.L., MARTIN-MARERO D., CHAHID A.,SENGER G., RISTIG M.L. Collective excitationsin liquid deuterium: neutron-scattering and correlated-density-matrix results.Physical Review В 47, 15097-15112(1993).

93FA221FARAGO В., MONKENBUSCH M., RICHTER D.,HUANG J.S., FETTERS L.J., CAST A.P.Collective dynamics of tethered chains: breathing modes.Physical Review Letters 71, 1015-1018 (1993).

93DE222DERIU A., CAVATORTA F., Dl COLA D.,MIDDENDORF H.D. Large scale structure and dynamicsof polysaccharide gels.Journal de Physique IV Cl, 237-247 (1993).

93KE223KENNEDY S.J., BROWN P.J., COLES B.R. A polarizedneutron study of the magnetic form factors in CeFe2.Journal of Physics: Condensed Matter 5, 5169-5178 (1993).

93KE224KEARLEY G.J., TROUW F.A high-resolution inverted time-of-flight spectrometerfor reactor cold-sources.Journal of Neutron Research 1,45-51 (1993).

93BO225BOUDJADA N.. RODRIGUEZ-CARVAJAL J., ANNE M.,FIGLARZ M. Dehydration of MoO3.2H2O: a neutronthermodiffractometry study.Journal of Solid State Chemistry 105, 211-222 (1993).

93CL226CLARKE S.J., COCKCROFT J.K., FITCH A.N.The structure of solid CF3I.Zeitschrift fuer Kristallographie 206, 87-95 (1993).

93VO227VOIT J. Charge transport and percolation in conductingpolymers.In "Chemical Physics of Intercalation II" P. Bernieret al. Eds. (Plenum Press, New York, 1993) pp. 291-298.

93BR228BROWN P.J. Magnetization distributions.International Journal of Modern Physics В 7, 3029-3048(1993).

93NE229NEEDHAM L.M., WILLIAMS V.G., TAYLOR A.D.A neutron scattering investigation of the magnetic formfactor for the intermultiplet transitions in Sm and SmPd3.Journal of Physics: Condensed Matter 5, 2591-2602 (1993).

м..93BR230BROWN P.J., FORSYTH J.B., TASSET F.Neutron polarimetry.

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FERRAND M., DIANOUX A.J., RETRY W., ZACCAI G.

Thermal motions and function of bacteriorhodopsinin purple membranes: Effects of temperature and hydrationstudied by neutron scattering.

Proceedings of the National Academy of Sciences 90,9668-9672(1993).

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JANOT C, BOISSIEU M. DE, BOUDARD M.,VINCENT H., DURAND M., DUBOIS J.M., DONG C.

A single-crystal x-ray diffraction studyof an A l 7 0 5 P d 2 | M n 8 5 icosahedral quasicrystal.

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JANOT С. The crystallography of quasicrystals.

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LLEWELLYN P.L., COULOMB J.P., GRILLET Y.,PATARIN J., LAUTER H.J., REICHERT H.,ROUQUEROL J. Adsorption by MFI-type zeolitesexamined by isothermal microcalorimetry and neutrondiffraction. 1. Argon, krypton and methane.Langmuir9, 1846-1851 (1993).

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REEHUIS M, BROWN P.J., JEITSCHKO W.,MOELLER M.H., VOMHOF T. A neutron diffractionstudy of the magnetic order in the ThCr2Si2 typephosphides PrCo2P2 and NdCo2P2.

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GODFRIN H. Adsorbed quantum gases.In "Excitations in Two-Dimensional and Three-DimensionalQuantum Fluids" A.G.F. Wyatt and H.J. Lauter Eds.(Plenum Press, New York, 1991) pp. 445-451.

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HENSLER J., BOYSEN H., BISMAYER U., VOGT T.

Ferroelastic transformation and crystal structure

of Ba-diluted lead phosphate, (Pbi.xBax)3(PO4)2.

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93LA238LAUTENSCHLAEGER G., WEITZEL H., VOGT T.,HOCK R., BOEHM A.. BONNET M., FUESS H.Magnetic phase transitions of MnWO4 studied by the useof neutron diffraction.Physical Review В 48, 6087-6098 (1993).

93KL239KLORA J., BOERNER H.G., EGIDY T.VON, GEORGII R..JOLIE J.. JUDGE S., KHITROV V.A., KRUSCHE В.,LIBMAN V.A., LINDNER H., LITVINSKY L.L.,MAYERHOFER U., MURZIN A.V., ROBINSON S.J..SUKHOVOJ A.M., TRIES H.Nuclear structure of I S 6Gd studied with (n, y), (n, e"), (d, p),(d, t) reactions and lifetime measurements.Nuclear Physics A561, 1-73 (19^3).

93KR240KRIMMEL A., LOIDL A., FISCHER P.. ROESSLI В.,DOENNI A., KITA K., SATO N.. ENDOH Y..KOMATSUBARA T., GEIBEL C., STEGLICH F.Single crystal neutron diffraction studies of the heavyfermion superconductor UPd2AI3.Solid State Communications 87, 829-831 (1993).

93MA241MARMEGGI J.C., LANDER G.H., BRUECKEL T.Progress towards producing a monodomain in the charge-density-wave state of alpha-uranium.Solid State Communications 87, 837-841 (1993).

93GO242GOMEZ-SAL J.C., ESPESO J.I., RODRIGUEZFERNANDEZ J., BLANCO J.A., RODRIGUEZCARVAJAL J. Crystallographic study and magneticstructures of CeNixPt].x and diluted related compounds.Solid State Communications 87, 863-868 (1993).

93H0243HOUSSAINI S., VERGNAT M., BRUSON A., MARCHAL G.,VETTIER C. Study of the hydrogen stabilityin evaporated amorphous Sij.xSnx: H (0<x<0.2) alloysby neutron scattering and exodiffusion measurements.Journal of Applied Physics 73,483-485 (1993).

93VI244VISSER D., BRAMWELL S.T.Determination of the interlayer superexchangein the two-dimensional ferromagnet Rb2CrCl4_4Brx

by means of quasielastic neutron scattering (abstract).Journal of Applied Physics 73, 5345 (1993).

93BR245BRAMWELL S.T., HOLDSWORTH P.C.W.Universality in two-dimensional magnetic systems.Journal of Applied Physics 73, 6096-6098 (1993).

93ME246MESOT J., ALLENSPACH P., STAUB U., FURRER A.,MUTKA H. Crystal field, phase separation, and percolativesuperconductivity in ЕгВа2СизОх (6<х<7) (abstract).Journal of Applied Physics 73, 6334 (1993).

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MORON M.C., PALACIO F., RODRIGUEZ-CARVAJAL J.

Antiterromagnetic behavior in S = 2 layered RbMnF4.

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BOENI P., ANDERSON I.S., BUFFAT P., ELSENHANS O.,FRIEDLI H.P., GRIMMER H., HAUERT R., LEIFER K.,PENFOLD J.. SOECHTIG J. Recent progress insupermirrors at PSI.

1CANS XII International Collaboration on AdvancedNeutron Sources. The Cosener's House, RutherfordAppleton Laboratory, Abingdon, May 24-28, 1993, pp. 1-8.

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On the infrared absorption of acidified water.

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WILLIAMS J.H., COCKCROFT J.K., FITCH A.N.

Structure of the lowest temperature phase of the solid

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AYACHE C , CURRAT R., HENNION В., MOLINIE P.

Anomalous features of the CDW transition in metallic 2Hdichalcogenides.

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CURRAT R., LORENZO-DIAZ J.E., MONCEAU P.,HENNION В., LEVY F. Neutron study of the Peierlstransition and low-frequency excitations in (TaSe^I.Journal de Physique IV, Colloque 2, 209-214 (1993).

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JOHNSON M.R., AIBOUT A., HORSEWILL A.J.,WILLIAMS J. The pressure dependence of methyltunnelling in acetylacetone.Journal of Physics: Condensed Matter 5, 7375-7386 (1993).

93PE2S4PETRY W., TRAMPENAU J., HERZIG C.Phonon dispersion of |3-Sc.

93BO255BONNETE F., EBEL C., ZACCAI G., EISENBERG H.Biophysical study of halophilic malate dehydrogenasein solution: revised subunit structure and solvent interactionsof native and recombinant enzyme.

Journal of The Chemical Society. Faraday Transactions, 89,2659-2666(1993).

93CH256CHATTOPADHYAY T. Modulated magnetic phases.International Journal of Modern Physics В 7,3225-3254(1993).

93R1257RIPERT M., POINSIGNON C., CHABRE Y.,PANNETIER J. Structural study of proton electrochemicalintercalation in manganese dioxide.Phase Transitions 32, 205-209 ( 1991 ).

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BALTA CALLEJA F.J., GONZALEZ ARCHE A.,EZQUERRA T.A., SANTA CRUZ C., BATALLAN F.,FRICK В., LOPEZ CABARCOS E. Structure and propertiesof ferroelectric copolymers of poly (vinylidene fluoride).Advances in Polymer Science 108, 1-48 (1993).

93JA259JANOT C., MAGERL A., FRICK В., BOJSSIEU M. DE.

Localized vibrations from clusters in quasicrystals.

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ARCHE A.G., BATALLAN F., BALTA CALLEJA F.J.,LOPEZ CABARCOS E., FRICK B. Molecular dynamicsin vinylidene fluoride-trifluoethylene IP(VF2/F1E)]ferroelectric copolymers.

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GALERA GOMEZ P., LOPEZ CABARCOS E., GEYER A. DE.SANS studies on micellar solutions of undecylammoniumchloride in presence of sodium chloride.In "Spanish Scientific Research Using Neutron ScatteringTechniques" GOMEZ SAL J. et al. Eds. (Universidade deCantabria, 1991) pp. 203-205.

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Determinacion del tamano y forma de micelas mediantedispersion de neutrones.In "XXIV Jornadas del Comité Espanol de la Detergencia"Comité Espanol de la Detergencia Tensiaactivos y AfinesEd., (Barcelona, 1993) pp. 337-351

PR Ч M.. ASMl viEN В., LANGEL W.,CAk, . i; C.J., В1.Л v H. Méthane rotationand the pi ase diagram of CH /xenon.Journal о! Chemical Physics 99. 2052-2058 (1993).

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93KN265KNELL U., WIPF H., LAUTER H.J., UDOVIC T.J.,RUSH J.J. A neutron-spectroscopy study of the hydrogenvibrations in hydrogen-doped ¥Ва2СизОх.

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93DO266DOSCH H., AL ULSAT K., LIED A., DREXEL W.,PEISL J. The evanescent neutron wave diffractometer:on the way to surface sensitive neutron scattering.Review of Scientific Instruments 63, 5533-5542 (1992).

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MARMEGGI J.C., LAUGIER J., FILHOL A.Simulation numérique et indexation en diffractométriede Laue: application aux transitions de phase.La Revue de Métallurgie - CIT/Science et Géniedes Matériaux, n°9, 1182-1182 (1993).

93LE268LEISURE R.G., SCHWARZ R.B., MIGLIORI A.,TORGESON D.R., SVARE I., ANDERSON I.S. Deuteriummotion in yttrium studied by ultrasonic measurements.Physical Review В 48, 887-892 (1993).

93PA269PANNETIER J., TRANQUI D., SLEIGHT A.W.Preparation and crystal structure of an oxide containing goldand mixed valent bismuth (Na2Bi l n

4Bi vAuO/|).Materials Research Bulletin 28,989-995 (1993).

93JU271JUNGCLAUS A., BELGYA T., DIPRETE P., VILLANI M.,JOHNSON E.L., BAUM E.M., MCGRATH C.A.,YATES S.W., ZAMFIR N.V. Lifetimes and electromagneticdecay properties of negative-parity states in 1 5 0 ' 1 5 2 - ' 5 4 Smfrom (n, n' Y) measurements.

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93SE272SEGUIN L., FIGLARZ M., PANNETIER J.A novel supermetastable WO3 phase.Solid State Ionics 63-65,437-441 (1993).

93VO273VOGL G., RANDL O.G., PETRY W., HUENECKE J.Quasielastic neutron scattering study of the Ni diffusionmechanism in the intermetallic alloy NiSb.Journal of Physics: Condensed Matter 5, 7215-7230 (1993).

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VATIN-PERIGNON N., OLIVER R.A.. GOEMANS P..KELLER F., BRIQUEU L., SALAS A.G.Geodynamic interpretations of plate subductionin the northernmost part of the central volcanic /one fromthe geochemical evolution and quantification of the crustalcontamination of the Nevado Solimana vok .11». southern Peru.

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PFEIFFER W., KOENIG S.. LEGK \ND J.F.. BAYERL T.,RICHTER D.. SACKMANN E. Neutron spin echo .sr Чof membrane undulations in lipid multihil.r TS.Europhysics Letters 23, 4c~-462 ( ICW

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TERECH P. 12-D-Hydroxyoctadecanoic acid oi i/iogcK:a small angle neutron scattering siudy.Journal de Physique 2. 2181 -2 i 95 ( 1993 ).

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SCHOPOHL N., WAX MAN D. On ihe moving A-B phaseboundary of superfluid 'He.

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BOIREAU A., SOUBEYROUX J.L., GRAVEREAU P..OLAZCUAGA R., LE FLEM (i. Evidence of copper pairingin Cu'2CrZr(PO4)3, acrystalloj;raphic study.

European Journal of Solid State and Inorganic Chemistry 30,337-346(1993).

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UWAHA M., SAITO Y. Roughening and smu , lung

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GELTENBORT P., OED A.Features of microstrip proportional counters.Proceedings SPIE 1737, 289-293 (1992).

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BUNE A.V., FRIDKIN V.M., VERKHOVSKAYA K.A.,LEGRAND J.F. Absorption changes at the phase transitionof ferroelectric copolymers doped by a cyanine dye.Ferroelectric.* 127, 221-224(1992).

93KE282KEARLCY G.J., CODDENS G., FILLAUX R,TOMKINSON J., WEGENER W. The effects of NH3

free rotation on the inelastic neutron scattering spectrumof Ni(NH3)2Ni(CN)4.2C6D6 at 20 K.Chemicaf Physics 176, 279-287 (1993).

93BO283BOIREAU A., SOUBEYROUX J.L., OLAZCUAGA R.,DELMAS C., LE FLEM G. Li intercalation in(Cu\S(II;0.5)Ti2(PO4)3: a neutron diffraction studyofLi 3 5 Cu 0 5 Tf 2 PO 4 ) 3 .Solid State Ionics 63-65, 484-487 (1993).

93DI284DIANOUX A.J., KNELLER G.R., SAUVAJOL J.L.,SMITH J.C. The polarized density of states of crystallinepolyacetylene. Molecular dynamics analysis and comparisonwith neutron scattering results.Journal of Chemical Physics 99, 5586-5596 (1993).

93VO285VOIT J. Charge-spin separation and the spectral propertiesof Luttinger liquids.Journal of Physics: Condensed Matter 5, 8305-8336 (1993).

93RI286RITTER C., NOELDEKE C., PRESS W., STEGE U.,SCHOELLHORN R. High Ni2+-mobility in the Chevrelphase Ni2Mo6S8: a quasielastic neutron scattering study.Zeitschrift fuer Physik В 92, 437-442 (1993).

93PL287PLAKHTY V., GOLOSOVSKY I., GUKASOV A.,SMIRNOV O., BRUECKEL T., CORNER В., BURLET P.Spin waves and exchange interactions in theantiferromagnetic garnets with Fe 3 + in the octahedral sites.Zeitschrift fuer Physik В 92,443-449 (1993).

93KO288KOEBLER U., APFELSTEDT I., FISCHER K., ZINN W.,SCHEER E., WOSNITZA J., LOEHNEYSEN H.V.,BRUECKEL T. Biquadratic exchange and critical behaviourin the diluted antiferromagnet EuxSri_xTe.Zeitschrift fuer Physik В 92, 475-487 (1993).

93ST289STEPANOV A.A., WYDER P., CHATTOPADHYAY T.,BROWN P.J., PILLION G., VITEBSKY I.M., DEVILLEA., GAILLARD В., BARILO S.N., ZHIGUNOV D.I.Origin of the weak ferromagnetism in Gd2CuO4.Physical Review В 48, 12979-12984 (1993).

93BR290BROWN P.J.Magnetic structure studied with zero-field polarimetry.PhysicaB 192, 14-24(1993).

93BO291BOUCHERLE J.X., HENRY J.Y., PAPOULAR R.J.,ROSSAT-MIGNOD J., SCHWEIZER J., TASSET F.,UIMING.Polarised neutron study of high-Tc superconductors.PhysicaB 192,25-38(1993).

93RO292RODRIGUEZ-CAR VAJAL J.Recent advances in magnetic structure determinationby neutron powder diffraction.

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93PE293PENDLEBURY J.M.Fundamental physics with ultracold neutrons.

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MURANI A.P., TAYLOR A.D., OSBORN R.,BOWDEN Z.A. Evolution of the spin-orbit excitationwith increasing Kondo energy in CeIn3_xSnx

93DO295DORNER B. Eigenvector determination - a dynamicalstructure determination. In "Proceedings of the Internationalseminar on structural investigations on pulsed neutronsources" (Joint Institute for Nuclear Research, Dubna, 1993)Report E-3-93-65 pp. 105-111.

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LISS K.D., MAGERL A., GLAESER W.A neutron diffraction study on the very narrow dynamicalwidth of GaAs [200].

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MURANI A.P., BOWDEN Z.A., TAYLOR A.D.,OSBORN R., MARSHALL W.G. Evidencefor localized 4f states in oc-Ce.Physical Review В 48, 13981-13984 (1993).

93BA298BARANOWSKI D., BUETTNER Helmut, VOIT J.Electron-libron coupling in polyaniline.Synthetic Metals 57,4608-4613 (1993).

93WA299WALKER M.B., BUYERS W.J.L., TUN Z., QUE W.,MENOVSKY А.Л., GARRETT J.D. Nature of the orderparameter in the heavy-fermions system URu2Si2.Physical Review Letters 71, 2630-2633 (1993).

93ВШООBUSSIERE A., GRIVOT P., KOSSAKOWSKI R.,LIAUD P., SAINTIGNON P. DE, SCHRECKENBACH K.A monochromatized chopped beam of cold neutronsfor low background experiments.Nuclear Instruments and Methods in Physics Research A332,220-223(1993).

93BR301BRAMWELL ST., G1NRAS M.J.P., HOLDSWORTH P.C.W.Temperature dependence of XY-like order parameters inthin free-standing smectic liquid-crystal films.Physical Review E 48, 625-627 (1993).

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KAPPLER C., WALKER M.B. Symmetry-based model forthe modulated phases of betaine calcium chloride dihydrate.Physical Review В 48, 5902-5909 (1993).

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AGTERBERG D.F., QUE W., WALKER M.B.Comment on "Structure and lattice dynamics of the orderedphase of solid Суд".Chemical Physics Letters 213, 207-208 (1993).

93FE304FEHST I., PAASCH M., HUTTON S.L., BRAUNE M.,BOEHMER R., LOIDL A., DOERFFEL M., NARZ T.,HAUSSUEHL S., MCINTYRE G.J. Paraelectric andferroelectric phases of betaine phosphite: structural,thermodynamic and dielectric properties.Ferroelectrics 138, 1-10(1993).

93MC305MCINTYRE G.J. Single-crystal diffractometrywith monochromatic x-rays and neutrons.

In "Neutrons and Synchrotron Radiation for CondensedMatter Studies. Volume 1. Theory" J. Baruchel et al. Eds.(Les Editions de Physique/Springer Verlag ,1993) pp.179-206.

93HI306HILFRICH K., SCHAERPF O., NEMBACH E.The state of order of grain-oriented iron-silicon transformersheets investigated by neutron scattering.

Journal of Applied Physics 74, 2354 2358 (1993).

93KA307KALOSKAMIS N.I., CHAN K.C., CHISHTI A.A.,GREENBERG J.S., LISTER C.J., FREEDMAN S.J.,WOLANSKI M., LAST J., UTTS B. The trigger detectorfor APEX: an array of position-sensitive Nal(Tl) detectorsfor the imaging of positrons from heavy-ion collisions.Nuclear Instruments and Methods in Physics Research A330,447-457(1993).

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KOLESNIKOV A.I., BARKALOV O.I., BELASH I.T.,PONYATOVSKY E.G., LASJAUNIAS J.C., BUCHENAUU., SCHOBER H.R., FRICK B. Neutron scattering andspecific heat study of AlGe and AISi alloys quenched underhigh pressure.Journal of Physics: Condensed Matter 5,4737-4748 (1993).

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GARC1A-MATRES E., RODRIGUEZ-CARVAJAL J.,MARTINEZ J.L., ALONSO J.A., SALINAS-SANCHEZA., SAEZ-PUCHE R. Polymorphism in the oxidesR2BaNiO5 (R = Tm, Yb, Lu).Solid State Ionics 63-65, 915-921 (1993).

93AL310

ALS-NIELSEN J., BRAMWELL S.T., HUTCHINGS M.T.,MCINTYRE G.J., VISSER D. Neutron scatteringinvestigation of the static critical properties of Rb2CrCl4.Journal of Physics: Condensed Matter 5,7871-7892 (1993).

93FR311

FRICK В., RICHTER D. Change of the vibrationaldynamics near the glass transition in polyisobutylene:inelastic neutron scattering on a nonfragile polymer.Physical Review В 47, 14795-14804 (1993).

93BO312

BOISSIEU M. DE, BOUDARD M., BELLISSENT R.,QUILICHINI M., HENNION В., CURRAT R., GOLDMANA., JANOT C. Dynamics of the AIPdMn icosahedral phase.Journal of Physics: Condensed Matter 5,4945-4966 (1993).

93JA313

JANOT C. Quasicrystals: structure and properties.In "International Conference on the Physics of TransitionMetals, Volume I", P.M. Oppeneer et al. Eds. (WorldScientific, 1993) pp. 310-317.

93ME314

MENGUY N., AUDIER M., BOISSIEU M. DE, GUYOTP.,BOUDARD M., JANOT С. Phason-phonon-assisted epitaxyat icosahedral-decagonal interfaces in Al-Pd-Mnquasicrystals.

Philosophical Magazine Letters 67, 35 (1993).

93DE315

DELEZE M., DRISSI S., KERN J., TERCIER P.A.,VORLET J.P., RIKOVSKA J., OTSUKA T., JUDGE S.,WILLIAMS A.P. Systematic study of the mixed ground-state and "intruder" bands in ' I 0 - ' 1 2 J 14Cd.Nuclear Physics A 551, 269-294 (1993).

93HA316HARDER A., MICHAELSEN S., JUNGCLAUS A.,LIEB K.P., WILLIAMS A.P., BOERNER H.G.Précision neutron binding energies of s9-61-63-64!^ and 9()Yobtained from thermal neutron capture reactions.Institute of Physics Conference Series 132, Section 1,69-71 (1993).

93FI317FILLAUX F., CARLILE C.J., KEARLEY G.J.Rotational tunnelling and the rotational potential of methylgroups in the zinc, manganese and cobalt chlorides saltsof 4-methy Ipy ridine.Molecular Physics 80,671-683 (1993).

93HE318HESSE M., FAUST H.R., FIONIG., GROSS M.,GOENNENWEIN F. New ionization chamber for the massspectrometer Lohengrin.In "Proceedings of Workshop on High ResolutionSpectroscopy of Fission Fragments, Neutrons and y rays"H. Maerten et al. Eds., (Forschungszentrum Rossendorf,1993) Report FZR-93-08 pp. 31-37.

93SC319SCHOBER H., STRAUCH D., DORNER B.Lattice dynamics of sapphire ( А^Оз).Zeitschrift fuer Physik В 92, 273-283 (1993).

93RE320RENKER В., GOMPF F., SCHOBER H., ADELMANN P.,BORNEMANN H.J., HEID R. Intermolecular vibrations inpure and doped C^Q. An inelastic neutron scattering study.Zeitschrift fuer Physik В 92,451-455 (1993).

93RE321RENKER В., GOMPF F., HEID R., ADELMANN P.,HEIMING A., REICHARDT W., ROTH G., SCHOBER H.,RIETSCHEL H. Neutron scattering study of intermolecularexcitations in solid С<ю and C70.Zeitschrift fuer Physik В 92, 325-329 (1993).

93AG322AGTERBERG D.F., WALKER M.B. Modelfor the anisotropic intermolecular potential for C 7 0 .Physical Review В 48, 5630-5633 (1993).

93LI323LINDGARD P. A., SCHMID B. Theory of singlet groundstate magnetism: application to field induced transitionsin CsFeCI3 and CsFeBr3.Physical Review В 48, 13636-13646 (1993).

93BO324BOERNER H.G., JOLIE J., °ENDLEBURY M.Workshop on high resolution gamma ray spectroscopy.Neutron News 4, n'-'l, 6 (1993).

93DI325DIANOUX A.J. Neutron scattering from liquids.

Neutron News 4, n'-'l, 6-7 (1993).

93FE326FERNANDEZ-DIAZ M.T., GARCIA-MATRES E.,GARCIA-MUNOZ J.L., MEDARDE M., RODRIGUEZ-CARVAJAL J., MARTINEZ J.L.Structural characterization of Cu and Ni oxides:a high resolution study by means of neutron techniques.

In "Superconductividad en Espana" F. Yndurain Ed.(Programa "Midas" Madrid, 1993) pp. 225-247.

93GA327

GARCIA-MUNOZ J.L., MEDARDE M., GARCIA-MATRES E., FERNANDEZ-DIAZ M.T., RODRIGUEZ-CARVAJAL J., MARTINEZ J.L. Magnetism of copperand nickel oxides studied by neutron techniques.In "Superconductividad en Espana" F. Yndurain Ed.(Programa "Midas" Madrid, 1993) pp. 251-276.

93WI328

WILLIAMS J.H. The molecular electric quadrupolemoment and solid-state architecture.

Accounts of Chemical Research 26, 593-598 (1993).

93WI330

WILLIAMS J.H., BECUCCI M. Vibrational Ramanspectroscopy of solid benzenerhexafluorobenzene.Chemical Physics 177, 191-202 (1993).

93WO331

WOUTERSEN A.T.J.M., MAY R.P., DE KRUIF C.G.

The shear-distorted microstructure of adhesive hard sphere

dispersions: a small-angle neutron scattering study.

Journal of Rheology 37, 71-88 (1993)

93VA332

VANATALU K., PAALME T., VILU R., BURKHARDT N.,JUENEMANN R., MAY R.P., RUEHL M., WADZACK J.,NIERHAUS K.H. Large-scale preparation of fullydeuterated cell components ribosomes from escherichiacoli with high biological activity.European Journal of Biochemistry 216, 315-321 (1993).

93MO333

MOELLER A., GOENNENWEIN F., KAUFMANN J.,PETROV G., DUERING I., MAERTEN H., RUBEN A.,GELTENBORT P., OED A. Cold fission studies usinga double-ionization chamber.In "Proceedings of the Workshop on High-ResolutionSpectroscopy of Fission Fragments, Neutrons and y-Rays"(Dresden, Germany, 1993) Report FZR-93-08 p. 24

P U B I / C A T / O N S - ILL-REPORTS

93FI334FILLAUX R, FONTAINE J.P., BARON M.H.,KEARLEY G.J., TOMKINSON J. Inelastic neutron-scatteringstudy of the proton dynamics in N-methylacetamide at 20 K.Chemical Physics 176, 249-278 (1993).

93CO335CORBETT J.D., ECKERT J., JAYASOORIYA U.A.,KEARLEY G.J., WHITE R.P., ZHANG J.Inelastic neutron scattering study of the metal clustercompound Li6(Zr6Cl|8H).Journal of Physical Chemistry 97, 8384-8386 (1993).

93OD336ODDOU J.L., JEANDEY C., BALLOU R., DEPORTES J.,OULADDIAF B. Moessbauer investigation of the peculiarmagnetism of Tb(Mn|. xFe x)2 at small substitutionof Fe for Mn.Solid State Communications 85, 419-422 (1993).

93LE337LELIEVRE-BERNA E., OULADDIAF В., CALERA R.M.,DEPORTES J., BALLOU R. Mn moment instabilityand magnetic structures of Tb]_xScxMn2.Journal of Magnetism and Magnetic Materials 123,L249-L254U993).

93NI338NIELD V.M., MCGREEVY R.L., CHIEUX P.,VERKERK P., VAN DER ENDE P. Continuityof short- range order at the melting/freezing pointin rubidium. Physica В 183, 70-74 (1994).

93KU339KUGLER S., PUSZTAIL., ROSTA L., CHIEUX P.,BELLISSENT R. Structure of evaporated pureamorphous silicon: neutron-diffraction and reverseMonte Carlo investigations.Physical Review В 48, 7685-7688 (1993).

93AN340ANDONOV P., CHIEUX P., KIMURA S. A local orderstudy of molten LiNbO3 by neutron diffraction.Journal of Physics: Condensed Matter 5,4865-4876 ( 1993).

93CH341CHARVOLIN J. Evolution of cylindrical structuresin the system sodium decylsulphate/decanol/water.

Liquid Crystals 13, 829-842 (1993).

93WI342WITZ J., TIMMINS P.A., ADRIAN M. Organizationof turnip yellow mosaic virus investigated by neutron smallangle scattering at 80 K: an intermediate state precedingdecapsidation of the virion ?Proteins: Structure, Function and Genetics 17,223-231 (1993).

93CL343CLEMENTS B.E., EPSTEIN J.L., KROTSCHECK E.,SAARELA M. Structure of boson quantum films.Physical Review В 48,7450-7470 (1993).

93CL344CLEMENTS B.E., KROTSCHECK E., SMITH J.A.,CAMPBELL C.E. Statistical mechanics of stronglycorrelated Bose quantum fluids.Physical Review В 47, 5239-5252 (1993).

93BA345

BAUD F., PEBAY-PEYROULA E., COHEN-ADDAD C.,ODANI S., LEHMANN M.S. Crystal structureof hydrophobic protein from soybean; a memberof a new cysteine-rich family.

Journal of Molecular Biology 231, 877-887 (1993).

93CH346CHRISTENSEN A.N., HAZELL R.G., LEHMANN M.S.,NIELSEN M. Crystal structure of 2-[N-morpholino]ethanesulfonic acid hydrate, C 6H 1 5NO 5S.Acta Chemica Scandinavica 47, 753-756 ( 1993).

93BO347BOUQUIERE J.P., FINNEY J.L., LEHMANN M.S.Interaction of the tetramethylammonium ion with thelysozyme molecule, studied using neutron diffraction.Journal of the Chemical Society. Faraday Transactions 89,2701-2705(1993).

93WI348

WILKINSON C., GABRIEL A., LEHMANN M.S.,ZEMB T.. NE F. Image plate neutron detector.Proceedings SPIE 1737, 324-329 (1992).

93LE349

LEHMANN M.S., ALS-NIELSEN J., GRUEBEL G.,LEGRAND J.F. Protein crystallographic measurementson BL9 (Troika) of the ESRF, February-March 1993.Joint CCP4 and ESF-EACBM Newsletter on ProteinCrystallography 28, 14- 5 (1993).

93CH350CHARVOLIN J., ROUX D., CANDAU S.

Auto-association des molécules amphiphiles.In "Grands Colloques de Prospective SMO. De la Matièreau Vivant: Systèmes moléculaires organisés",(1993) PP. 31-37.

93SH351SHAPIRO S.M., SVENSSON E.C., VETTIER C ,HENNION B. Uniaxial-stress dependence of the phononbehavior in the premartensitic phase of Ni62.5Al37 5.Physical Review В 48, 13223-13229 ( 1993)!

93HO352HOUSSAINI S., VERGNAT M, BRUSON A., MARCHAL G.,MANGIN P., VETTIER C. Evidence of hydrogenmodulation in amorphous germanium preparedby reactive evaporation.Applied Physics Letters 63, 2109-2111 (1993).

93GA353GAILHANOU M., BAUMBACH T., MARTI U., SILVA P.C.,RE1NHART F.K., ILEGEMS M. X-ray diffractionreciprocal space mapping of a GaAs surface grating.Applied Physics Letters 62, 1623-1625 (1993).

93DE354DESCOTES L., BELLISSENT R., PFEUTY P.,DIANOUX A.J. Dynamics of liquid sulphur aroundthe equilibrium polymerization transition.PhysicaA20I,38l-385(l993).

93DE355FERRAND M., PETRY W., DIANOUX A.J., ZACCAI G.Dynamical transition of bacteriorhodopsin in purplemembranes revealed by neutron scattering: a relationbetween structure, dynamics and function.Physica A 201,425-429 (1993).

93BU356BUCHENAU U., NUECKER N.. DIANOUX A.J.,KRAUSE D. Fast relaxations in a silicate glass.Physica A 201, 372-374 (1993).

93ZE357ZEPPENFELD K., POETTGEN R., REEHUIS M.,JEITSCHKO W., BEHRENS R.K. Preparation of Yb2Cr2C3

and magnetic properties of the carbidesR2Cr2C3 (R=Y,Gd-Lu) with Ho2Cr2C3 -type structure.Journal of Physics and Chemistry of Solids 54,257-261 (1993).

93GE3S8GEYER A. DE. Phase behavior of surfactant-alcohol-oil-water cubic liquid crystals.Progress in Colloid & Polymer Science 93, 76-80 (1993).

93SA359SAARELA M., CLEMENTS B.E., KROTSCHECK E.,KUSMARTSEV F.V. Phase transitions in the growthof 4He films.Journal of Low Temperature Physics 93,971-985 (1993).

93PE360PEREZ-VILLAR V., VAZQUEZ-IGLESIAS M.E.,GEYER A. DE. Small-angle scattering studiesof chlorpromazme micelles in aqueous solutions.Journal of Physical Chemistry 97, 5149-5154 (1993).

93BA361BATLLE X., OBRADORS X., MEDARDE M.,RODRIGUEZ-CARVAJAL J., PERNET M.,VALLET-REGI M. Surface spin canting in BaFe,2O19

fine particles.Journal of Magnetism and Magnetic Materials 124,228-238(1993).

93MO362MORON M.C., PALACIO F., RODRIGUEZ-CARVAJAL J.Crystal and magnetic structures of RbMnF4 and KMnF4investigated by neutron powder diffraction: the relationshipbetween structure and magnetic properties in the Mn- +

layered perovskites AMnF4 (A = Na, K, Rb, Cs).Journal of Physics: Condensed Matter 5,4909-4928 (1993).

93TO363TOMEY E., ISNARD O., PAGAN A., DESMOULINS C.,MIRAGLIA S., SOUBEYROUX J.L., FRUCHART D.Modulation of spin reorientation transitions in the seriesR(Fe, M),2Xy (R = Y, Nd. Ho ; M = Mo, Ti : X = N, H).Journal of Alloys and Compounds 191, 233-238 (1993).

93BL364BLESA M.C., AMADOR U., MORAN E., MENENDEZ N.,TORNERO J.D., RODRIGUEZ-CARVAJAL J.Synthesis and characterization of nickel and magnesiumferrites obtained from cc-NaFeO2.Solid State Ionics 63-65,429-436 (1993).

93FE365FERNANDEZ-DIAZ M.T., MARTINEZ J.L.,RODRIGUEZ-CARVAJAL J. High temperature phasetransformation of oxidized R2NiO4+5 (R = La, Pr and Nd)under vacuum.Solid State Ionics 63-65, 902-906 (1993).

93FO366FORSYTH V.T., LANGAN P., MAHENDRASINGAM A.,MASON S.A., FULLER W. The location of ionsand water around the D conformation of DNA.In "Water-Biomolecule Interactions" M.U. Palma et al. Eds.(SIF, Bologna, 1993) Conference Proceedings 43,231-234(1993).

93RI367RITTER C., NOELDEKE C., PRESS W.,SCHOELLHORN R. High Ni2+-mobility in the Chevrelphase Ni2Mo6S8: a quasielastic neutron scattering study.Zeitschrift fuer Physik В 92,437-442 (1993).

93DA368DARDEL В., MALTERRE D., GRIONI M., WEIBEL P.,BAER Y., VOIT J., JEROME D. Possible observationof a Luttinger-liquid behaviour from photoemissionspectroscopy of one-dimensional organic conductors.Europhysics Letters 24, 687-692 (1993).

93AN369ANDONOV P., CHIEUX P., KIMURA S., WASEDA Y.Local order refinement in liquid niobate usinga two radiation method (x-rays and neutrons).Zeitschrift fuer Naturforschung A 48, 955-964 (1993).

93LA370

LANGAN P., FORSYTH V.T., MAHENDRASINGAM A.,ALEXEEV D., MASON S.A., FULLER W.Complementary x-ray and neutron fibre diffraction studiesof the distribution of water and cations around the A-DNAdouble helix.

In "Water-Biomolecule Interactions" M.U. Palma et al. Eds.(S1F, Bologna, 1993) Conference Proceedings 43,235-238(1993).

93BO371

BOERNER H.G., JUNGCLAUS A., ULBIG S., JOLIE J.High resolution gamma ray spectroscopy and its applicationto y-ray induced Doppler broadening.Acta Polytechnica 33, 87- 92 (1993).

93KL372

KLAUMUENZER S., PETRY W., SCHUMACHER G.A search for particle tracks in the metallic glass PdsoSi?o.Nuclear Tracks and Radiation Measurements 19,907-910(1991)

93HO373

HOHLWEG G., HOLZER В., PETRY W., STROBL G.,STUEHN B. Neutron scattering study of segmentaidynamics in the disordered regions of partially crystallinepolyethylene.

Macromolecules 25, 6248-6254 (1992).

93LE374

LE CAER G., MALAMAN В., ISNARD O.,SOUBEYROUX J.L., FRUCHART D., JACOBS Т.Н.,BUSCHOW K.H.J. Magnetic characterisationof the ternary carbide ThFe, ,CX ( 1.5<x<2) by 5 7 FeMoessbauer spectroscopy.

Hyperfine Interactions 77, 221-234 (1993).

93GU37S

GUILLAUME F., EL BAGHDADI A., DIANOUX A.J.Dynamics of alkyl-type chains in crystals.Physica Scripta T49, 691 -698 ( 1993).

93IS376

ISNARD O., MIRAGLIA S., SOUBEYROUX J.L.,FRUCHART D., DEPORTES J., BUSCHOW K.H.J.Structural study and magnetic characterization ofTh 2Fei 7D 5, Th2Fe,7CxH -_x and Th 2 Fe| 7 N 3

Journal of Physics: Condensed Matter 5, 5481-5490 (1993).

93RI377RICHTER D., WILLNER L., ZIRKEL A., FARAGO В.,FETTERS L.J., HUANG J.S. Onset of topologicalconstraints in polymer melts: a mode analysis by neutronspin echo spectroscopy.Physical Review Letters 71, 4158-4161 (1993).

93SU378SUCK J.B. Collective excitations in disordered systems.International Journal of Modern Physics В 7,3003-3028(1993).

93BR380BRUECKEL T., PAULSEN C., PRANDL W., WEISS L.Magnetic structure phase transition and magnetizationdynamics of pseudo-ID CoNiTAC mixed crystals.Journal de Physique: Série I, 3, 1839-1859 (1993).

93CH381CHIEUX P. Introduction to accurate structure factormeasurements of disordered materials by neutron scattering.Journal of Molecular Structure 296, 177-198 (1993).

93KN382

KNELL U., HEID C., WIPF H., UDOVIC T.J., RUSH J.J.,LAUTER H.J. Hydrogen in YBa2Cu3Ox: a neutronspectroscopy and a nuclear magnetic resonance study.Zeitschrift fuer Physikalische Chemie 179, 397-401 (1993).

93TE383TEN KATE H.H.J., HARTMANN R.A., ZEYEN C.M.E.,TEN HAKEN В., VAN DE KLUNDERT L.J.M.Construction of optimized superconducting spin precessionmagnets for neutron spectroscopy.IEEE Transactions on Magnetics 25, 1688-1691 (1989).

93MO384

MOMPEAN F.J., MARTIN-MARERO D., GARCIA-HERNANDEZ M., BERMEJO F.J., FAK В., MARTINEZ J.L.,SENGER G., RISTIG M. Collective excitationsin liquid deuterium in three thermodynamic states.Journal of Molecular Structure 296, 313-320 (1993).

93SC385SCHERM R., GUCKELSBERGER K., SZPRYNGER A.,FAK B. The dispersion of sHe quasiparticle.s in He IIfrom neutron scattering.Journal of Low Temperature Physics 93, 57-83 (1993).

93AS386ASGHAR M., BOUCHENEB N., MEDKOUR G.,GELTENBORT P., LEROUX B. Measurement of coldfission for 2 2 9Th(n t h, f), 2 3 2U(n t h,f) and 2 3 9Pu(n,h f)with the Cosi fan tutte spectrometer.Nuclear Physics A 560,677-688 (1993).

93MA387

MARTINEZ J.L., BERMEJO F.J., GARCIA-HERNANDEZ M., ALONSO J., MOMPEAN F.J.Collective excitations in a molecular glass.Springer Series in Solid State Sciences 112, 301-302 (1993).

93AE388

AEBERSOLD M.A., GUEDEL H.U., HAUSER A.,

FURRER A., BLANK H., KAHN R. Exchange interactionsin mixed Yb3+-Cr3+ and Yb3+-Ho3+ dimers: an inelas'.ic-neutron-scattering investigation of Cs3Yb| 8 Cr 0 2 Br 9 andCs3Yb, KHo() 2Br9.

93RA389

RAMSAY J.D.F., LINDNER P.

Small-angle neutron scattering investigations of the structureof thixotropic dispersions of smectite clay colloids.Journal of the Chemical Society Faraday Transactions 89,4207-4214(1993).

93LE390

LEGRAND J.F. Morphology and structure of polymerelectrets and ferroelectric polymers.

IEEE Transactions on Electrical Insulation 28, 336-343(1993).

93SC391

SCHLAPBACH L., ANDERSON I., BURGER J.P.

Hydrogen in metals.in "Materials Science and Techniques" Buschow K.H.J. Ed.(VCh., 1993) pp. 271-331.

93KR392

KRUEGER J.K., PRECHTL M., WITTMANN J.C.,MEYER S., LEGRAND J.F., D'ASSEZA G. Structure andproperties of semi-crystalline polymers via high frequencyacoustic and x-ray measurements. I - FerroelectricP(VDFAYFe) copolymer.Journal of Polymer Science В 31, 505-512 (1993).

93ES393

ESSER A., THIELENS N.M., ZACCAI G. Small angleneutron scattering studies of C8 and C9 and their interactionsin solution.Biophysical Journal 64, 743-748 (1993)

93CE394

CENDRIN F., CHROBOCZEK J., ZACCAI G.,EISENBERG H., MEVARECH M. Cloning, sequencingand expression in Escherichia coli of the gene codingformalate dehydrogenase of the extremely halophilicarchaebacterium haloarcula marismortui.Biochemistry 32,4308-4313 (1993).

93LI395LINDER K., FRICK В., BUCHENAU U.Debye-Waller factors in amorphous polymers.PhysicaA201, 112-114(1993)

93FR396FRICK В., RICHTER D., TREVINO S. Inelastic fastrelaxation in a weakly fragile polymer glass near Тц.Physica A 201, 88-94 ( 1993 )

93BA397BARTSCH E., FUJARA F., GEIL В., KIEBEL M.,PETRY W., SCHNAUSS W., SILLESCU H., WUTTKE J.Signatures of the glass transition in a van der Waals liquidseen by neutrons and NMR.Physica A 201, 223-236 (1993)

93AC398ACHIBAT T., BOUKENTER A., DUVAL E., FRICK В.,GARCIA N., SERUGHETT1 J. Comparison between lightand neutron inelastic scatterings. The frequency linearbehaviour of the light-vibration coupling coefficient.Physica A 201, 257-262 (1993)

93ZO399

ZORN R., RICHTER D., FRICK В., FARAGO B.Neutron scattering experiments on the glass transitionof polymers.

Physica A 201,52-66(1993)

93FA400FANJAT N., BARJ M., BRIAT В., SCHAERPF O.,LUCAZEAU G. Study of inelastic magnetic excitationsin №зСг2(РО4)з by neutron scattering.Journal of Physics and Chemistry of Solids 54,1515-1526(1993)

2. Without ILL authors and co-authors(Code number 1001 to 1025).

93BE1001

BERNHOEFT N. Low energy neutron scatteringin the vicinity of the superconducting phase transition.Neutron News4, n'Jl, 21-23 (1993).

93DU1002

DUBOIS M., GULIK-KRZYWICKI T., CABANE В.Growth of silica polymers in a lamellar mesophase.Langmuir 9, 673-680 (1993).

93NE1003NELMES R.J., MCMAHON M.I., PILTZ R.O.,WRIGHT N.G. High-pressure neutron-diffraction studiesof KH2PO4-type phase transitions as Tc tends to OK.Ferroelectrics 124, 355-360 ( 1991 ).

93L01004LOVEDAY J.S., NELMES R.J., MAHON M.I.M.,ALLAN D.R.. KALDIS E., KARPINSKIJ., RAVEAU В.,CA1GNAERT V. Structural studies of copper-oxidesuperconductors.Ferroelectrics 128, 93-98 (1993).

93EC1005ECKERT J,. KUBAS J. Barrier to rotationof the dihydrogen ligand in metal complexes.Journal of Physical Chemistry 97, 2378-2384 (1993).

93NU1006NUDING M., LAMPARTER P., STEEB S. Short rangestructure of amorphous electrodeposited СгдоСюНюand Сг7зС|2Н|5 alloys by means of x-ray and neutrondiffraction.Journal of Non-Crystalline Solids 156-158, 181 -184 ( 1993).

93LE1007LE ROY J.. PACCARD D., BERTRAND C.,SOUBEYROUX J.L.. BOUILLOT J., PACCARD L.,SCHMITT D. Magnetic structures of Nd2Fe2Si2Cand TbiFe2Si2C.Solid State Communications 86,675-678 (1993).

93 WI1008WINTER R., PILGRIM C., HENSEL F., MORKEL C.,GLAESER W. Structure and dynamicsof expanded liquid alkali metals.Journal of Non-Crystalline Solids 156-158, 9-14 (1993).

93SA1009SACERDOTE-PERONNET M., MENTZEN B.F.Location of perdeuterated benzene sorbed at low pore-fillingin a H-MFI material: a neutron powder diffraction study.Materials Research Bulletin 28. 767-774 (1993).

93PE1010PERKINS S.J., SMITH K.F., KILPATRICK J.M.,VOLANAKIS J.E., SIM R.B. Modelling of the serine-proteinase fold by x-ray and neutron scatteringand sedimentation analyses: occurrence of the foldin factor D of the complement system.Biochemichal Journal 295, 87-99 (1993).

93РЕ10ПPERKINS S.J., SMITH K.F., SIM R.B. Molecularmodelling of the domain structure of factor I of humancomplementby X-ray and neutron solution scattering.Biochemical Journal 295. 101-108 (1993).

93LU1012LUTZ H.D., PFITZNER A., COCKCROFT J.K.Structural phase transition and nonstoichiometryof LJ2FeCl4-neutron diffraction studies.Journal of Solid State Chemistry 107, 245-249 (1993).

93BA1013

BARTLETT P., OTTEWILL R.H. Goemetric interactions

in binary colloidal dispersions.

LangmuirS, 1919-1925(1992).

930T1014

OTTEWILL R.H. Experimental methodsof particle characterization.

Pure and Applied Chemistry 64, 1697-1702 (1992).

93OT1015

OTTEWILL R.H. Adsorption of surfactantsat interfaces - studies by small-angle neutron scattering.Progress in Colloid and Polymer Science 88,49-57 (1992).

93MI1016

MILLS M.F., GILBERT R.G., NAPPER D.H.,RENNIE A.R., OTTEWILL R.H. Small angle neutronscattering studies of inhomogeneities in latex particlefrom emulsion homopolymerizations.

Macromolecules 26, 3553-3562 (1993).

93BA1017

BARTLETT P., OTTEWILL R.H. A neutron scattering

study of the structure of a bimodal colloidal crystal.

Journal of Chemical Physics 96, 3306-3318 (1993).

93CL1018

CLAPPERTON R.M., INGRAM B.T., OTTEWILL R.H.,RENNIE A.R. NMR spectroscopic and neutron scatteringstudies on ammonium decanoate-ammoniumperfluorooctanoate mixtures.ACS Symposium Series 501, 268-277(1992).

93WI1019

WINTER R., PILGRIM C , HENSEL F. The static and

dynamic structure factor of expanded liquid alkali metals.

Journal de Physique IV C5,45-50 ( 1991 ).

93PA1020

PAUL D.MCK. FORGAN E.M., CUBITT R., LEE S.L.,YETHIRAJ M., MOOK H.A. The flux-line latticein high-temperature superconductors.PhysicaB 192,70-78(1993).

93AE1021

AEPPLI G., HAYDEN S.M., MOOK H.A.. MASON Т.Е.,TAYLOR A.D., CLAUSEN K.N., PERRING T.G.,CHEONG S.W., FISK Z., RYTZ D. From insulator to metalwith hot and cold neutrons.

Physica В 192, 103-108 (1993).

93BE1022BEST S., FORSYTH J.B., TREGENNA-PIGGOTT P.L.Influence of the stereochemistry of water co-ordinationto metal (HI) cations on the M-O bond lengthand electronic structure of the cation.Journal of the Chemical Society. Dalton Transactions2711-2715(1993).

93LA1023LANDER G.H. Neutron elastic scatteringof actinides and anomalous lunthanides.In "Handbook on the Physics and Chemistry of the RareEarths. Vol. 17", K. Gschneidner et al. Eds.(North-Holland, Amsterdam, 1993) pp. 635-702.

93ME1024MENDES E.. GIRARD В., PICOT С., BUZIER M.,BOUE F., BASTIDE J. Small angle neutron .scatteringstudy of end-linked gels.Macromolecules 26,6873-6877 (1993)

93LA1025LANDER G.H. Neutron and synchrotron x-ray scatteringexperiments on actinides.PhysicaB 186-188,664-669(1993).

AUTHOR INDEX

Author IndexPublicationsand ILL-Reports 1993

ABELE H.ACHIBAT T.ADELMANN P.

ADRIAN M.AEBERSOLD M.A.AEPPL1 G.AGERON P.AGTERBERG D.F.

AIBOUT A.AL ULSAT K.ALEGR1A A.ALEXEEV D,ALLAN D.R.ALLENSPACH P.

ALONSO J.A.

ALS-NIELSEN J.

ALVAREZ F.AMADOR U.ANDERSON I.S.

ANDONOV P.

ANDREJTSCHEFF W.ANNE M.AOUIZERAT-ELARBY A.APFELSTEDT 1.ARBE A.ARCHE A.G.ARMBRUSTER P.ARNAUDAS J.I.ASGHAR M.ASMUSSEN B.

AUDIER M.

AYACHE C.BAER Y.BALDOCEOLINM.BALLAUFF M.BALLOU R.

BALTA CALLEJA F.J.

BARANOWSKI D.

BARILO S.N.BARJ M.

93ABI7193AC39893RE320

93RE32193WI34293AE388

93 AE 102193FA09T93AG303

93AG32293JO253

93DO26693ARI3.S93LA370

93LOI00493ME154

93ME 1 6493ME24693RO20393ST193

93MA38793GA13493GA30993AL31093LE34993AR13593BL36493SC39I93BO24893LE26893AN34093AN36993PE124

93BO22593DU15893KO28893AR13593AR260

93FI19993MO14293AS38693ASI2393PR26393BO11293ME31493AY25I93DA36893BA120

93MA19693LE337

93OD33693AR26093BA25893BA20593BA29893ST28993FA400

BARKALOV O.I.BARNES P.BAROCCH1 F.

BARON M.H.BARTLETT P.

BARTSCH E.

BASTIDE J.

BATALLAN F.

BATESON R.D.BATLLE X.BAUD F,BAUM E.M.BAUMBACH T.BAYERL T.BEAUFILS J.P.BECUCCI M.BEELI C.BEHRENS R.K.BEILLEJ.BEINERTG.BELASH I.T.

BELGYA T.BELLISSENT R.

BENA 1.BENABED A.BENETTI P.BERGE В.BERMEJO F.J.

BERNHOEFT N.BERNSTEIN E.BERTAGNOLLI H.BERTHOLD H.J.BERTRAND C.BEST S.BISMAYER U.BLAISEA.BLANCHIN M.G.BLANCO J.A.BLAND J.A.C

BLANK H.93 AS 123

BLESA M.C.

93KO30893TU15793BA17093BA18693BA218

93F133493BAI01393BA10I7

93BAI2993BA397

93WU20693BAI3693BA189

93ME102493AR2609^BA25893BA19I93BA36I93BA34S93,1 U 271

93GA35393PF27593BE10693WI33093BO1I293ZE35793FE101

93BA18993KO308

93JU27193BOI13

93BO31293DE354

93KU33993BE18793FA09T93BAI2093REI8793BE219

93BE22093CH 1 52

93CH21793MA38793MO38493BE100I93BE17993BA12993BE1I9

93LEI(H)793BEI022

93HE23793PA14593BEI7993GO24293BA19I93 PA 19093AE388

93BL20893LA14693PR26393BL364

BOBISUT F.BOEHM A.BOEHMER R.BOENI P.BOERNER H.G.

BOERS1G B.BOIREAU A.

BOISSIEU M. DE

BONNET M.BONN ETE F.BORDAS S.BORNEMANN H.J.

BOUCHENEB N.BOUCHERLEJ.X.BOUDARD M.

BOUDJADA N.BOUE F.

BOUILLOTJ.

BOUKENTER A.BOUQUIEREJ.P.

BOWDEN Z.A.

BOYSEN H.BRAMWELL S.T.

BRANTS.BRAUNE M.BRENTANO P. V.BRIAT B.BRIQUEU L.BRISSOTR.BROWN P.J.

93BA12093LA23893FE30493BO24893BO32493PE05T93BOI6693BO37I93HA3I693JU102

93KL23993GOI7893BO27893B028393 ВОН 293BOI1393 ВО 18593 ПОЗ 1293JA23293JA259

93ME3I493LA238

93ВО25593Т020493RE32093RE32I93AS38693ВО29193 ВОН 293BOI 1393BOI8593 ВОЗ 1293JA232

93МЕ31493ВО22593ВА13693В А 189

93 M El 02493CR2I3

93LE100793АС39893BO16I93ВО34793MU29493MU29793НЕ23793AL31093BRI5693BRI7493BR24593BR30I93VI24493PEI2493FE30493JU10293FA4(H)93VA274

93WAI6293BR22893BR23093BR29093КЕ22393РА145

AUTHOR INDEX

BRUECKELT.

BRUSON A.

BUCHENAU U.

BUCHRR B.BUETTNER Helmut

BUFFAT P,BUNEA.V.BURGER J.P.BURKHARDT N.BURLET P.

BUSCHOW K.H.J.

BUSSIERE A.BUTERA R.BUYERS W.J.L.BUZIER M.

CABANE В.CAIGNAERTV.CAMPBELL C.E.CANDAU S.CANNON R.D.CAPELLMANN H.CARLILEC.J.

CASTEN R.F.CAVATORTA F.CELINSKI Z.CENDRIN F.CHABRE Y.CHAHIDA.

CHAN K.C.CHARVOLINJ.

CHATTOPADHYAY T.

CHEONG S.W.CHEVRIER J.CHI EUX P.

93RE23593ST28993BR38093KO28893MA24I93PL287

93H024393HO35293BU35693K0308

93L139593R020393BA20593BA29893BO24893 В U 28193SC39193VA33243 PA 14593PL28793IS376

93LE37493BU30093R1I07

93WA29993BAI36УЗВА189

93MEI02493DUI00293L01004

93CL34493CH35093JA20793SCI5093FI3I7

93 LA 14693PR26393JUI02

93DE22293BA19193CE39493RI257

93BE2I993BE22093CHI5293CH21793KA30793CH34I93CH35093CH25693SC12893ST289

93AEI02193CH20093AN34093AN36993BAI2993BAI7093BAI8693BA2I893CH38I93DUI5893HOI92

CHISHTI A.A.CHRISTENSEN A.N.CHROBOCZEKJ.CLAPPERTON R.M.CLARKE S.J.CLAUSEN K.N.CLAVAGUERA N.CLAVAGUERA-MORA M.T.CLEMENTS B.E.

COCKCROFTJ.K.

CODDENS G.COHEN-ADDADC.COLES B.R.COLMENEROJ.CONVERT P.COOK J.C.COQUET E.CORBETTJ.D.COULOMB J.P.

COWLAM N.CRETTEZJ.M.CRIADOA.

CUBITT R.CULLENJ.CURRAT R.

CUTRONI M.CYROT-LACKMANN F.D'ASSEZA G.D'HONDTP.DARDEL B.DAVID A.DAY P.DEKRUIFC.G.DELAPLANE R.G.DELEZE M.DELFS C.D.DELMAS C.DEN BROEDER F.J.A.DEPORTES J.

DERIU A.DESCOTES L.DF.SMOULINS C.

93KU33993MA202

93NI33893ROI5993ROI6093KA30793CH34693CE394

93CLI01893CL226

93AEI02193TO20493TO20493CLI1693CL34393CL34493SA359

93LUIOI293SCII893 W 1 250УЗС1.22693FIII7

93VO14493KE28293BA34593KE22393ARI3593ZA198

93COOIG93CR2I393CO33593LL234

93ZAI9893CR21393BE2I993CH2I7

93PAI02093MO14293AY25I93BOII393BO3I293CU25293 LOI 8393NEI6793KL1I493KR392

93WAI6293DA36893BAI2993DAI4I

93W033193KEI4793DE31593DAI4I93BO28393PAI90931S376

93LE33793OD33693DE22293DE35493TO363

DEV1LLE A.Dl COLA D.DIANOUX A.J.

DIPRETE P.DJURADO D.DOENNI A.

DOERFFEL M.DONG C.DORE J.C.DORNER B.

DOSCH H.DREXEL W.DRISSI S.DRUYTS S.DUBBERS D.DUBOIS J.M.

DUBOIS M.DUERING I.DUPUY J.DURAND M.DUVAL E.EASTOEJ.EBEL C.ECKERT J.

EGIDY T.VON

EISENBERG H.

EL BAGHDADI A.ELSENHANS O.ENCISO E.ENDOH Y.EPSTEIN J.L.ESPESOJ.I.ESSER A.ETCHEBEST C.EWEN B.

EZQUERRA T.A.PAGAN A.FAKB.

FANJAT N.

93ST28993DE22293BU35693DE35493DE35593DI28493DI325

93DU15893FE23I

93GU37593NEI6793SA12293JU27193SA12293 DO 10993KR24093FE30493JA23293STI97

931Ю29593PL28793SC21593SC3I993ST2I4

93DO26693DO26693DE31593DRI7293ABI7I93BO1I293JA232

93MA202

93DU100293MO33393DUI5893JA232

93AC39893ST197

93BO25593CO335

93EC100593PEI2493KL23993BO25593CE39493GU37593BO24893CHI5293KR24093CL34393G024293ES39393FEI63

93EWI3793RII0793RI138

93BA25893TO363

93MO38493SC38593FA10893FA400

AUTHOR INDEX

FARAGO B.

FAUST H.R.

FEHST I.FERNANDEZ-DIAZ M.T

FERRAND M.

FETTERS L.J.

FIGGIS B.N.FIGLARZ M.

FILHOL A.FILLAUX F.

PILLION G.FINNEMORE O.K.FINNEY J.L.

FIONI G.

FISCHER E.W.FISCHER J.E.FISCHER K.FISCHER P.

FISK Z.FITCH A.N.

FLEGER H.W.FOGELBERG B.FONTAINE J.P.FORD G.W.

FORGAN E.M.FORSYTH J.B.

FORSYTH V.T.

FOURCAUDOT G.FREEDMAN S.J.FREY F.

93EWI3793FA22193RI10793RI13893RI377

932O39993FA09T93GOI78

93FII9993HE31893FE30493FE36593FE10193FE326

93GA32793DE35593FEI6393FE23I93FA22I93RII0793RI13893RI377

93DA14I93BO22593SE272

93MA26793FI31793FI334

93KE28293ST28993SCI2893BOI6193BO34793FI199

93HE31893MA19693SA12293KO28893DO109

93FI13393KR24093RO203

93 AE 102193CL22693FII17

93VOI4493WI25093LAI4693FA09T93FI334

93BAI9I93FOI95

93PA102093BEI02293BR23093FOI2I93FO36693LA10393LA37093KL11493KA30793PR209

PRICK B.

FRIDKIN V.M.FRIEDLI H.P.FRUCHART D.

FUESS H.

FUJARA F.

FULLER W.

FURRER A.

GABRIEL A.GAILHANOU M.GAILLARD B.CALERA GOMEZ P.

CALERA R.M.GARCIA N.GARCIA-HERNANDEZ M.

GARCIA-MATRES E.

GARCIA-MUNOZJ.L.

GARRETTJ.D.CAST A.P.GAY J.M.GEHRING P.M.GEIBEL C.CEIL B.GELTENBORT P.

93AC39893AR13593AR26093BA25893FR31 193FR39693JA259

93K030893LI395

93ZO39993BU28193BO24893IS376

93LE37493TO36393HOI2593LA23893MI2H)

93WU20693BA39793FO12I93F036693LA10393LA37093AE38893DO10993MEI5493ME16493ME24693RO20393STI9393WI34893GA35393ST289

93GA26I93GA26293LE33793AC39893BE2I993BE22093CHI5293CH21793MA38793MO38493FE326

93GAI1093GA13493GA30993GA32793FE326

93GA32793WA29993FA22193PAI90

93MOI4293KR24093BA39793AS38693DRI7293GE06T93GE28093GO178

GEORGII R.GEYER A. DE

GIAMARCHI T.GIBIN D.GILBERT R.G.GINRAS M.J.P.GIRARD B.GLAESER W.

GODFRIN H.GOEMANS P.GOENNENWEIN F.

GOLDMAN A.

GOLDMANN M.GOLOSOVSKY I.GOMEZ-SAL J.C.GOMPF F.

GONZALEZ ARCHE A.GRAVEREAU P.GREENBERG J.S.GRILLET Y.GRIMMER H.GRINTER R.GRIONI M.GRIVOT P.GROSS M.

GRUEBEL G.GUCKELSBERGER K.GUEDEL H.U.GUETHOFF F.GUGLIELMI A.GUILLAUME F.GUKASOV A.GULIK-KRZYWICKI T.GUYOT P.HARDER A.

HARRISON D.H.HARTMANN R.A.HAUERT R.HAUSER A.HAUSSUEHLS.HAYASHI S.HAYDEN S.M.

HAZELL R.G.HEGER G.HEIDC.HEID R.

HEIDEMANN A.HEIMING A.

93MO33393KL23993GA26I93GE35893PE36093GI211

93BA12093MI101693BR301

93MEI02493LI296

93 WI 100893G023693VA274

93FII9993G017893HE3I8

93MO33393B01I393BO3I293RE18793PL287

93GO24293RE32093RE32193BA25893BO27893KA30793LL23493BO24893JA207

93DA36893BU30093FI199

93HE3I893LE34993SC38593AE38893GUI8293BAI2093GU37593PL287

93DUI00293ME3I493HA18493HA3I693HAI4993TE38393BO24893AE38893FE304

93HO17393 AE 102193DOI0993N034693BOI1293KN38293RE32093RE32193HOI7393GUI8293RE32I

AUTHOR INDEX

HE1NRICH B.HELLMANN E.H.HELLMANN G.P.HELM G.

HENNION B.

HENRY J.Y.HENSEL F.

HENSLER J.HERZIG C.

HESSE M,

HEW AT A.W.HIGHMORE R.J.

HILFRICH K.

HOCK R.

HOFFMANN H.

HOFMANN S.

HOHLWEG G.

HOLDSWORTH P.C.W.

HOLZER B.HOPPE U.

HORSEWILL A.J.

HOUSSAINI S.

HUANG J.S.

HUENECKE J.HULLIGER F.HUTCHINGS M.T.

HUTTON S.L,HYUN O.B.

IBARRA M.R.IBBERSON R.M.IBEL K.

ILEGEMS M.INGRAM B.T.ISNARD O.

JACOBS Т.Н.JACOBSON L.JALJ.F.JANOT C.

93BAI9193HEI3993HE139

93AB171

93AY25193BOI1393BO31293CU25293GUI82

93LO18393SH35I93BO291

93WII00893 WHO 19

93HE23793GU18293PE25493TRI69

93FI199

93HE318

93FI13393ZA198

93HII5I93HI306

93HOI2593LA238

93PII3I

93PII31

93HO37393BR15693BR24593BR30I

93HO37393HOI92

93HOI7393JO253

93HO243

93HO35293VE10493FA22I93RI107

93RI138

93RI377

93VO27393DO10993AL310

93FE30493SCI28

93RII5593RII5593STI97

93GA35393CLIOI8

93IS37693LE37493TO363

93LE37493FA09T93DUI5893BOII2

93BOU3

93BOI85

JANSSEN E.JAYASOORIYA U.A.

JEANDEY C.

JEITSCHKO W.

JERICHA E.JEROME D.

JILEK E.

JOHNSON E.L.JOHNSON M.R.JOHNSON M.T.JOLIE J.

JONES S.L.

JOVEN E.JUDGE S.

JUENEMANN R.

JUNGCLAUS A.

KAHN R.

KALDIS E.

KALOSKAMIS N.I.KALUS J.

KANIA U.

KAPPLER C.KARPINSKI J.

KAUFMANNJ.KEARLEY G.J.

KEEN D.A.

KELLER F.KELLERSOHN T.KENCONO A.W.KENNEDY S.J.

KERN J.KHITROV V.A.

93BO3I293JA07T93JA08T93JAI94

93JA232

93JA23393JA25993JA313

93ME3I4

93PAI90

93CO33593JA207

93OD336

93RE23593ZE35793TEI6893DA368

93FII33

93RO20393JU27I

93JO25393PA190

93BOI66

93BO32493BO37I93JU10293KL239

93TU157

93MO142

93DE3I593KL23993VA332

93BO37193HA31693JUI0293JU27I

93AE388

93FI13393LO1004

93RO20393KA307

93PII3I93ABI7I93KA302

93FI13393LOI004

93RO203

93M033393BL20893CO335

93FI317

93FI33493JA207

93KE22493KE28293PR209

93VA274

93KEI4793PII3I

93KE223

93DE3I593KL239

KIEBEL M.

KILPATRICK J.M.

KIMURAS.

KITA K.KLAUMUENZER S.KLEIN T.

KLORA J.KNELL U.

KNELLER G.R.KNOEZINGER E.

KOEBLER U.KOELKER W.

KOENIG S.KOLESNIKOV A.I.

KOMATSUBARA T.

KOSSAKOWSKI R.

KRAUSE D.KRIMMELA.KROTSCHECK E.

KRUEGER J.K.KRUSCHE B.

KUBAS J.

KUGLER J.

KUGLER S.KUHS W.F.KULDA J.

KUSMARTSEV F.V.

LAMPARTER P.LANDER G.H.

LANGAN P.

LANGEL W.

LARTIGUE C.

LASJAUNIAS J.C.

LAST J.

LAUGIERJ.

LAUTENSCHLAEGER G.LAUTER H.J.

LECAERG.LE FLEM G.

93BA39793WU20693PE101093AN340

93AN369

93KR24093KL37293KLII4

93KL239

93KN265

93KN38293DI284

93LAI46

93K0288

93HI15193PF275

93KO30893KR240

93BU300

93BU35693KR24093CLI16

93CL343

93CL34493SA35993KR39293KL239

93EC100593MAI96

93KU33993MC17593HO125

93SA359

93NU100693MA24193PAI45

93LAI023

93LAI02593FO12I93FO36693LAI0393LA370

93LAI46

93PR26393BAI3693BA189

93LI264

93CH20093KO30893AB17I93KA307

93MA26793LA23893LL23493BA19I93CL1I6

93KN26593KN38293LAI4693PA19093LE374

93BO278

AUTHOR INDEX

LE ROY J.

LEE S.LLEGRANDJ.F.

LEHMANN M.S.

LEIFER K.LEISURE R.G.LEL1EVRE-BERNA E.LEROUX B.LEVY F.

LI J.C.LIATARD E.LIAUD P.LIBMAN V.A.LIEB K.P.

LIED A.LINDER K.LINDGARD P.A.LINDLEY P.P.LINDNER H.LINDNER P.

LISS K.D.LISTER C.J.LITVINSKY L.L.LLEWELLYN P.L.LOEHNEYSEN H.V.

LOEWENHAUPT M.LOIDL A.

LOPAC V.LOPEZ CABARCOS E.

LORENZO J.E.LORENZO-DIAZ J.E.LOVEDAY J.S.LUCAZEAU G.

LUTZ H.D.

MACDIARMID A.G.

93BO28393CR2I3

93LEI00793PA102093BU28I93DU15893KR39293LE349

93LE39093PF27593REI8793BA34593BOI6I

93BO347

93LEI8893LE349

93N034693WI348

93BO24893LE26893LE33793AS38693CU252

93LO18393LI264

93FA09T93ВШОО93KL23993HA18493HA31693JUI02

93DO26693LI39593LI323

93B016I93KL23993BAI36

93MA196

93PI13I93RA389

93L1296

93KA30793KL23993LL23493KO28893STI2693STI2693FE304

93KR24093PEI2493AR26093BA25893GA26I93GA26293LOI8393CU252

93LOI00493FA10893FA400

93LU10I293SCII893SAI22

MAERTEN H.MAERZ K.MAGERL A.

MAGLI R.

MAHENDRASINGAM A.

MALAMAN B.

MALTERRE D.MALUGANI J.P.

MANGIN P.

MARCHAL G.

MARETM.MARMEGGIJ.C.

MARSHALL W.G.MARTI U.MARTIN-MARERO D.

MARTINEZ B.MARTINEZ J.L.

MASCHKE U.MASON S.A.

MASON Т.Е.MATTIOLI F.MAY R.P.

MAYERHOFER U.

MCDONALD 1.MCEWEN K.A.MCGRATH C.A.MCGREEVY R.L.MCINTYREG.J.

93M033393MAI9693HOI2593JA25993LI296

93BAI7093BAI8693BA2I893 FOI 2193FO36693LAI0393LA37093LE374

93DA36893 ROI 5993 ROI 6093HO35293VEI0493H024393HO35293VEKW

93MA20293MA24I93MA767

93МШГ793GA3S393BE220

93MO38493FE10I93BE21993BE22093CH15293CH2I793EWI8I93FEIOI93FE32693FE365

93GAIIO93GAI3493GA30993GA32793MA38793M038493EW13793 FOI 2l93FO366

93LAI0393LA370

93 AE 102193BAI20931 IA 149

93VA33293WO33I93KL239

93MA03T93PEI24

93STI9793BWI8I

93JU27I93NI338

93AL3IO93FE304

MCMAHON M.l.

MEDARDE M.

MEDKOUR G.MENDES E.

MENENDEZN.MENGUY N.MENOVSKY A.A.MENTZEN B.F.

MERCIER R.

MESOTJ.

MEVARECH M.MEYERS S.MEZZETTO M.MICHAELSEN S.

MIDDENDORF H.D.MIEHEG.MIGLIORI A.MILLS M.F.MIRAGLIA S.

MISBAH C.MOELLER A.MOELLER M. H.MOLINIE P.

MOMPEAN F.J.

MONCEAU P.

MONKENBUSCH M.MOOK H.A.

MOORE P.B.MORAL A. DELMORAN E.MORKEL C.MORON M.C.

MOUDDEN H.MUELLFR H.H.MUELLER U.MUENZENBERG G.MURANI A.P.

93KEI4793MC305930L14093PTI48

93MCI7593NEI00393LOI004

93BA361

93FE32693GA32793AS38693BA13693BA189

93MEI02493BL364

93ME31493WA29993SAI009

93ROIS993ROI6093ME15493MEHv493ME246

93R020393STI9393CE39493KR392

93BA12093HA18493HA31693DE222

93MI21093LE268

93MIIOI693IS376

93TO36393BE187

93MO333

93RE23593AY25I93MUI0593MUI1I93BE2I9

93BE22093MA38793MO38493CU25293LOI8393FA22I

93AEI02I93PAI02093HAI4993MOI4293BL364

93 WI 100893M024793M036293BOII393LEIS893MI21093FII99

93MU294

AUTHOR INDEX

MURSIC Z.MURZ1N A.V.MUTKA H.

MUTTERER M.NAPPER D.H.NARZ T.NAST-L1NKE U.

NEF.NEDER R.B.NEEDHAM L.M.

NELMES R.J.

NEMBACH E.

NESVIZHEVSKY V.V.

NEUMAIER S.NIELD V.M.NIELSEN M.NIERHAUS K.H.NINA M.NISSEN H.U.NOELDEKE C.

NORMAN C.J.NOZIERES P.

NUDING M.NUECKER N.

NUETZEL K.O'CONNELL R.F.OBRADORS X.

ODANI S.

ODDOUJ.L.ODIER P.OEDA.

OESER R.

OLAZCUAGA R.

OLIVER R.A.OLOVSSON 1.

OSBORN R.

OTSUKA T.OTTEWILL R.H.

93MU297MHO 12593KL239M M E 154M M E 164MME246

MMUIOS93MUI11MMU2I293RO20393ST193

MGO17893MI10I6

MFE304MGOI78

MWI34H93PR209MNE16793NE229

93LOI004

MMCI75М1МЕКЮЗ

93HI15I93HI306

93NE04T93GOI78MNI338

93NO346

93VA33293FE16393BO11293RI28693RI367

93TU15793GI2I1

93 NO 13293NU1006

93BU35693SC2I593FOI9593BA36193FEIOI

93BA34593OD33693FEI0193GE280

93MO333

93BA13693BA18993BO27893BO28393VA27493KE14793OL14093PTI48

93ME16493MU29493MU29793DE3I5

93BA10I393BAIOI793CL10I8

OULADDIAFB.

PAALME T.PAAR V.PAASCH M.PACCARD D.PACCARD L.PAIXAOJ.A.PALACIO F.

PANNETIER J.

PAPOULAR R.J.

PARES G.PASYUK V.V.PATARIN J.PAUL D.MCKPAULSEN C.

PAULUS W.PAYEN C.

PAYER A.PEBAY-PEYROULA E.

PEISLJ.PENDLEBURY J.M.

PENFOLDJ.PEREZ-VILLAR V.PERKINS S.J.

PERNET M.PERRING T.G.PETKOV P.PETRENKO A.V.PETROV G.RETRY W.

PFEIFFER W.PFEUTY P.PFITZNER A.PIAFE COLLABORATIONPICOT С.PIGRAM W.J.PILGRIM C.

PILSL H.

93MII01693OTIOI493OT10I5

93LE33793OD33693VA33293PEI2493FE304

93LE100793LE1007

93PAI4593M024793M036293CR21393PA269

93RI25793SE27293PA02T93BO29IM K L 1 I 493PA19093LL234

93PAI02093BR380

93PA16593MUI0593MU11I93PAI6593BA345

93DO26693PE293

93BO32493PE05T93BO248

93PE36093PE10H)93PEIOII93BA36I

93AE1021

93PEI2493PA190

93MO33393BA397

93DE35593FE231

MGU 18293HII51

93ЫО37393KL37293PE25493TR16993VO273

93WU20693PF275

93DE35493LU10I2

93FA09T93ME1024

93LAI03MWI100893WII019

93PI13I

PILTZ R.O.

PINSTON J.A.PLAKHTY V.POETTGEN R.POINSIGNON C.POMME S.PONYATOVSKY E.G.PRAGER M.

PRANDL W.PRECHTL M.PRESS W.

PREVEL B.PROFFEN T.PTASIEWICZ-BAK H.

PUGLIERIN G.PUSZTAI L.QUEW.

QUILICHINI M.

RAMSAY J.D.F.RANDL O.G.

RAVEAU B.RAVELLE-CHAPU1S R.REATTO L.

REEHUIS M.

REICHARDT W.REICHERT H.REINHART F.K.RENAULT A.RENKER B.

RENNIEA.R.

RESSOUCHE E.REYNOLDS P.A.RICHTER D.

RIETSCHEL H.RIKOVSKAJ.RIPERT M.RISTIG M.

RITTER C.

93MC17S93NE1003

93FA09T93PL28793ZE35793RI257

93DR17293KO30893ASI2393LAI46

93PR26393BR38093KR39293AS12393RI28693RI367

93DUI5893PR209930L14093PT14893BA12093KU33993AG303

93WA299

93BOII393BO31293RA38993VO273

93LO100493BEI7993BA17093BA18693RE23593ZE35793RE32193LL23493GA35393REI8793RE320

93RE32193CLI018

93HEI3993MIIOK1

93PA02T93DA14I93EWI3793FA221

93FR31193FR39693PF27593RI10793RI13893RI377

93ZO39993RE32193DE31593RI257

93MO38493BE220

93MOI4293PAI65

93RII55

AUTHOR INDEX

ROBINSON B.H.ROBINSON S.J.

RODRIGUEZ FERNANDEZ J.RODRIGUEZ-CARVAJAL J.

ROESSLI B.

ROSENBERG H.M.ROSS O.K.ROSSAT-MIGNODJ.ROSTA L.ROTH G.ROUQUEROLJ.ROUSSELOT C.

ROUX В.ROUX D.RUBEN A.RUCKENSTEIN A.E.RUEHL M.RUSH J.J.

RUSIECKI S.RYTZ D.SAARELA M.

SACERDOTE-PERONNET M.SACKMANN E.SAEZ-PUCHE R.

SAINTIGNON P. DESAÎTO Y.

SALAMON M.B.SALAS A.G.SALINAS-SANCHEZ A.

SANTA CRUZ C.SATO N.SAUVAJOLJ.L.

SAVAGE H.F.J.

93RI24693RI367

93TU15793ST19793KL23993PEI24

93G024293BA36193BE17993BL36493BO22593FEIOI

93GO24293FE32693FE365

93GAIIO93GAI3493GA30993GA32793MO24793MO36293RO29293KR24093RO20393NE16793LI264

93BO29I93KU33993RE32I93LL23493ROLS993RO16093FEI63

93CH35093MO333

93GI2II93VA33293KN26.S93KN382

93FI13393AEI02I

93CL34393SA359

935АКЮ993PF275

93GAIIO93GAI3493GA30993BU3(K)93SA180

93UWI7793UW27993MO14293VA27493GA1IO93GA13493GA30993BA25893KR24093DI28493SAI2293BOI6I

SCHAERPF O.

SCHEER E.SCHERM R.SCHERR E.M.SCHLAPBACH L.SCHLICHENMAIER R.SCHMAHL W.W.SCHMIDB,SCHMIDT C.SCHMITTD.

SCHNAUSS W.SCHNEIDER M.SCHOBER H.

SCHOELLHORN R.

SCHOPOHL N.SCHRECKENBACH K.SCHROEDER A.SCHUMACHER G.SCHWARZ R.B.SCHWEDA E.SCHWEIZER J.SCONZA A.SEGUIN L.SEKI S.SENGER G.

SERUGHETTI J.SEVERING A.SHAPIRO S.M.SILLESCU H.

SILVA P.C.SIM R.B.

SLEIGHT A.W.SMIRNOV O.SMITH J.A.SMITH J.C.

SMITH K.F.

SOECHTIG J.SOMEKH R.E.SOUBEYROUX J.L.

STACHEL D.

93FA40093HII5193HI30693SC12893SC15093KO28893SC38593SA12293SC39193SC12793VO153

93LI32393AB17I

93LEHH)793BA39793SCII893RE32093RE32I93SC2I593SC2I693SC3I993KO30893PAI6593RI28693RI367

93SC27793BU30093STI2693KL37293LE26893SCI2793BO29193BAI2093SE27293SAI8093BE220

93MO38493AC39893STI2693SH35193BA 1 2993BA397

93WU20693GA35393PEIOIO93PEIOI 193PA269

93PL28793CL34493DI28493FE163

93PEIOIO93PEIOII93BO24893ZA19893BO27893BO28393IS376

93LE100793LE37493TO36393HOI92

STASSIS C.STAUB U.

STEEB S.STEGE U.STEGLICH F.STEIGENBERGER U.STEPANOV A.A.STEYTLER D.C.STIRLING W.G.STRAEHLEJ.STRAUCH D.

STRIDE J.A.STROBL G.STROKA B.STUEHN B.STUHRMANN H.B.SUCKJ.B.

SUKHOVOJ A.M.SUZUKI T.SVARE 1.SVENSSON E.C.SZPRYNGER A.TACHEZ M.

TANG Г.С.TARLING S.E.TASSET V.

TAYLOR A.D.

TEN HAKEN B.TEN KATE H.H.J.TERBURG B.P.TERCIER P.A.TERECH P.THEOBALD J.P.THIELENS N.M.TIMMINS P.A.TOMEY E.TOMKINSON J.

TORGESON D.R.TORNERO J.D.TORRELLES X.

93GUI8293MEI5493MEI6493ME24693RO20393ST193

93NUI00693RI286

93KR24093EW18I93ST28993ST19793PAI4593SCI2793SC2I593SC2I693SC3I993ST21493JA207

93HO37393STI26

93HO37393LEI8893CH2(X)93KLI1493SUI1593SU20193SU37893KL23993DOI0993LE26893SH35I93SC38593RO15993RO16093PA14593TU15793BO29I93BR23093DAI4I93PA02T93BAI7D93BAIhO93MEI64

93 AE 102193MU29493MU29793NE22993TE38393TE38393TE16893DE3I593TE276

93GO17893ES39393WI34293TO36393FI334

93KE28293LE26893BL36493TO204

A U T H O R INDEX

TRAMPENAUJ.

TRANQUI D.TRAPPMANN T.TRAUTVETTER H.P.TREGENNA-P1GGOTT P.L.TREVINO S.TRIEB H.TROUNOV V.TROUW F.TUNZ.TURRILLAS X.UDOVIC TJ.

UIMING.ULBIGS.

ULBRICHTW.URBAN G.UWAHA M.

VALANCE A.VALLET-REGI M.VAN DE KLUNDERT L.J.M.VAN DER ENDE P.VANATALU K.VARMA C.M.VATIN-PERIGNON N.VAZQUEZ-IGLESIAS M.E.VERGNAT M.

VERKERK P.

VERKHOVSKAYA K.A.VETTIER C.

VILLANI M.VILU R.VINCENT H.

VISENTIN L.VISSER D.

VITEBSKY I.M.VOGLG.VOGTO.VOGTT.

VOITJ.

93GUI8293PE25493TRI6993PA26993ST12693DR172

93BE102293FR39693KL23993FI133

93KE22493WA29993TU15793KN26593KN38293BO29193BO37193JU10293PII3I

93MAI9693SAI80

93UWI7693UW17793UW27993BEI8793BA36193TE38393NI338

93VA33293GI211

93VA27493PE360

93HO24393HO35293VE10493NI33893TEI6893BU28I93HO24393H035293SH35193VE10493JU271

93VA33293BO11293JA232

93BA12093AL3IO93VI24493ST289

93V027393PA14593BE1I993HE23793HOI2593LA23893MI21093SC12793VO14493V015393BA20593BA298

VOLANAKIS J.E.VOMHOFT.VONHOLDT E.VORLETJ.P.WADZACK J.WAGEMANS C.

WALKER M.B.

WARTCHOW R.WASEDA Y.WAXMAN D.WEBER H.W.WEGENER W.WEIBEL P.WEISS L.WEITZEL H.WHITE R.P.

WILKINSON C.WILLIAMS A.P.

WILLIAMS J.H.

WILLIAMS W.G.WILLNER L.WINTER R.

WIPF H.

WITTMANN J.C.WITZJ.WOLANSKI M.WOSNITZA J.WOUTERSEN A.T.J.M.WRIGHT N.G.

WUTTKE J.

WYDER P.YATES S.W.YETHIRAJ M.ZACCAI G.

ZAMFIR N.V.

93DA36893VO13093VO22793VO28593PEIOK)93RE23593BE1I993DE31593VA33293DRI7293WA16293AG30393AG32293KA30293WA29993BEI1993AN36993SC27793SCI2893KE28293DA36893BR38093LA23893CO33593JA20793WI34893HA18493DE3I593HA3I693BR17493WII4393WI24993WI25093JO25393WI32893WI33093NE22993R1377

93 Wl 100893WI10I993KN26593KN38293KR39293WI34293KA30793KO28893WO33193MCI75

93NEI00393BA397

93WU20693ST28993JU27I

93PAI02093B025593CE39493DE35593ES39393FE16393FE23193JU10293JU27I

ZARBAKHSHA. 93ZAI98ZAWISKY M. 93TEI68ZEMB T. 93WI348ZEPPENFELD K. 93ZE357ZEYEN C.M.E. 93PR209

93TE383ZHANG J. 93CO335ZHIGUNOV D.I. 93ST289ZIELINSKIF. 93BAI36

93BAI89ZINN W. 93K0288ZIRKEL A. 93RI377ZOLLIKER M. 93RO203ZORN R. 93ZO399

PAPERS ACCEPTED FOR PUBLICATIONS

Papers acceptedfor Publication1. Neutron Instruments and MethodsBOERNER H.G.. PENDLEBURY J.M.

New developments lor the nuclear and fundamental physics facilities

in the high flux reactor of the ILL Grenoble.

8th International Symposium on Capture Gamma Ray Spectroscopy

Fribourg. Swil/erlaml, .September 20-24. 1993 (93BÔS04S).

ELSENHANS ().. BOKNI P.. FRIEDLI H.P.. GRIMMER H.. BUFFAT P..

I.EIFIiR K.. SOECHTIG J., ANDERSON l.S.

Nett de\ clopinent ol'Ni/Ti supermirrors for neutron optics.

Thin Solid Films ( ' Ш 1 Л 321.

E1.SHNHANS ().. ANDERSON I., BOENI P.. BUFFAT P., FRIEDLI H.P..

GRIMMER H.. HAUERT R.. LEIFER K.. SOF.CMTIG J.

Artificial multilayer supcrmirrors for neutron optics.

Proceedings of the "4th Interiiationul Colloquium on Plasma Processes",

Anlibes-Juan-lcs-Pins. France. June 6-11. 1993 (93EL5133).

GRIMMER H.. B^ENI P., ELSENHANS O.. FRIEDLI H.P.. LEIFER K..

BUFFAT P.. ANDhRSON l.S.

Characterization of multilayers for neutron optics.

Proceedings of the 3rd European Powder Diffraction Conference. Vienna.

Austria. September 25-28. 1993 (93GR5I34).

HEIDEMANN A.

New methods in high resolution neutron spectroscopy.

PhysicaB(93HE5ll3).

HOLY V.. BAUMBACH T.

Non-specular X-ray reflection from rough multilayers.

Physical Review (93HO5I25).

JUNGCLAUS A.

The gamma ray induced Doppler (GRID) broadening method:A status report.

Proceedings of the 8th International Symposium on Capture Gamma RaySpeclroscopy and Related Topics. Fribourg. Switzerland, September 20-24,I993I93JU5091).

LISS K.-D.. MAGERL A.

Can a gradient crystal compete with a mosaic crystal as a monochromator

in neutron- or X-ray diffraction ?

Nuclear Instruments and Methods A (93LI5067).

MAGERL A.. LISS K.-D.. DOLL C.. MADAR R., STEICHELE E.

Will gradient crystals become available for neutron diffraction ?

Nuclear Instruments and Methods A (93MA5068).

MIKULA P.. KULDA J.. LUKAS P.. VRANA M., WAGNER V..SCHERM R.

Bent perfect crystals in asymmetric diffraction geometry in neutronscattering experiments.

Nuclear Instruments and Methods A (93MI5I29).

MUTKA H.

Coupled time and space focusing for time-of-flight inelastic scattering.

Nuclear Instruments and Methods A (Proceedings of the Workshop

"Focussing Bragg Optics", PTB Braunschweig, Germany.

May 10-11. 1993) (93MU5032).

MUTKA H.Energy-resolved small-angle thermal neutron scattering:a challenge for instrumentation.Proceedings of the International Conference on Quasielustic Neutron

Scattering '93, Future Prospects on High-Resolution Inelastic NeutronScattering, San Sebastian, Spain. September 27-28. 1993 (93MU5074).

ROSSBFUG А.. PIECHOTKA M., MAGERL A., KALD1S E.Mapping of the structural perfection of vapour grown a-Hgb crystalsby means ofy-ray rocking curves.Journal of Applied Physics (93RO5090).

SCHAERPFO.. ANDERSON l.S.The role of surfaces and interfaces in the behaviourof non polarizing and polarizing supermirrors.Physic» В (93SC5I24).

VRANA M.. LUKAS P.. MIKULA P., KULDA J.

Bragg diffraction optics in high resolution strain measurements.

Nuclear Instruments anil Methods A (93VRS128).

WILLIAMS C. ZKYEN C.M.E.. RliM Р.Г.

Optimal Larmur precession field shapes : Application to neutron spinecho three-axis spectrometer.Measurement Science and Technology (93ZE5047).

2. TheoryBRAMWELL ST.. HOLDSWORTH P.C.W.

Can the universal jump be observed in two-dimensional XY magnets?

Journal of Applied Physics (93BR5094).

BRAMWELL ST.. G1NGRAS M.J.P.. REIMERS J.N.

Order by disorder in an anisolropic pyrochlore lattice antifcrromagnet.

Journal of Applied Physics (93BR509S).

CLEMENTS B.E., KROTSCHNECK E., LAUTER H.J., SAARELA M.

Structure and growth of quantum films.

PhysicaB(93CL5M7),

CLEMENTS B.E., KROTSCHECK E., LAUTER H.J., SAARELA M.

Temperature dependence of third sound in helium monolaycrs.

PhysicaB(93CL5ll8).

CLEMENTS B.E., FORBERT H., KROTSCHECK E., LAUTER H.J..SAARELA M.

Dynamics of quantum films.PhysicaB(93CL5119).

CLEMENTS B.E.. FORBERT H., KROTSCHECK E.. SAARELA M.

''He on weakly attractive substrates: Structure, stability

and wetting behaviour.

Journal of Low Temperature Physics (93CLS120).

CLEMENTS B.E., F KROTSCHECK E., SAARELA M.

Analytic structure of long-wavelength excitations in 4 He surfaces.

Zeitschrift fuer Physik В (93CL5121).

CLEMENTS B.E.. KROTSCHECK E., LAUTER H., SAAKELA M.

Recent progress in the theory of bose liquid films.

Nova Science Publishers. Commack. NY, New York, Vol. 9 (93CL5122).

NOZIERES P.

Some comments on Bose Einstein condensation.

Proceedings of the Trento Conference on Bose Einstein Condensation,

Trent», Italy. June 1993 (93NO5052).

P A P E R S A C C E P T E D FOR PUB i /c ATIO N s

NOZIERI-S P.

The Grinfcld instability »l° stressed crystals.

Proceedings of the NATO Advanced Research Workshop

on Spatio-Temporal Puucms in Non-equilibrium Complex Systems,

Santa K\ N M., USA, April 13-17. 1993 <93NO50S4).

VOITJ.

Charge-spin separation and the spectral properties of Luttingcr liquids.Proceedings of ihe NATO Advanced Research Workshop "The Physicsand Mathematical Physics of the Hubbtird Model". San Sebastian, Spain,October 3-Х. 1493. ed. O.K. Campbell, J.M.P. Carmelo. and F. Guinea,Plenum Press. N.Y. (1994) (93VOJ063).

3. Fundamental and Nuclear PhysicsASGHAR M.. BOUCIIENHB N.. MEDKOUR a., GELTENBORT P.,LHKOUX B.Measurement of cold fission for ~'Thln l h,f), 2 3 2U(n u l,f) and 234Pu(nu,.f)with the Cosi-Fan-Tulte spectrometer.Journal of Nuclear Physics A (93AS5098).

DEWEY M.S., KESSLER E.G., Jr., GREENE G.L., DESLATTES R.D.,SACCHETTI F.. PETRILLO C.. FREUND A.. BOERNER U.C..ROBINSON S.. SCHILLEBEECKS P.Structure factors in germanium at 0.342 MeV and 1.382 MeV.Physical Review В (93DE5152).

DRUYTS S.. WAGEMANS C., GELTENBORT P.Determination of Ihe •15Cl(n,p)'WS reaction cross-sectionand its astrophysical implications.Journal of Nuclear Physics A (93DR5096).

FIONI G.. FAUST H.R.Review of nuclear charge distribution from (пц,, Г) experimentsat the Lohengrin spectrometer.Proceedings of II. International Conference on Dynamical Aspectsof Nuclear Fission, Smolonice, Slovakia, June 1993 (93FI5042).

JUNGCLAUS A., BOERNER H.G.

High resolution gamma spcctroscopy with ideal crystals.Nuclear Instruments and Methods.

JUNGCLAUS A.. CASTEN R.F., GILL R.L., BOERNER H.G.Levels in ' 6 s E r above 2 MeV and the onset of chaos.Physical Review С (93JU5040).

SCHILLEBEECKX P.. WAGEMANS C., GELTENBORT P.,

GOENNENWEIN K. OED A.Investigation of mass, charge ;;nd energy of •м'Ри(пц1,Г) fragmentswith the Cosi-Fan-Tutle spectrometer.Journal of Nuclear Physics A (93SC5097).

4. Structural and Magnetic excitationsEVEN J., BERTAULT M.. TOUDIC В., CAILLEAU H., FAVE J.L.,CURRAT R.. MOUSSA F.

Dynamics of the phase transition of the fully polymerized and dcuteratcddiacelylene 2,4-hexadiynylcne bis(p-toluencsulfonate).

Physical Review В (93EV5I09).

KAMBA S.. PETZELT J., ZELEZNY V.. SMUTNY F., DVORAK V.,IILINKA J., QUILICHINI M., VOLKOV A.A., GORSHUNOV B.P.,KOXLOV G.V., CURRAT R., LEGRAND J.F.Dynamical studies of fully deutcrulcd BCCD.

Fcrroeicctrics (Proceedings of the 8lh International Meeting on

Ferroclcclricity, Gaithersburg, Maryland, USA, August 8-13, 1993)(93KASI39).

POUCET S., ALBA M., NOGUliS M.

Static critical properties of disordered fcrromagncts studied

by SQUID magnetometry and SANS techniques.

Journal of Magnetism and Magnetic Materials (93P05093).

POUSSIGUE G.. BENOIT С., BOISSIEU M. DE, CURRAT R.

Inelastic neutron scattering by quasi-crystals: a model for icosahedral

Al-Mn: for Al-Mn-Pd comparison with Ihe experimental results.

Journal of Physics: Condensed Matter (93PO5I3H).

ROSOV N.. LYNN J.W., KAESTNER J., WASSERMANN E.F.,

CHATTOPADHYAY T., BACH II.

Temperature dependence of the magnetic excitations in ordered

and disordered FcyiPiin-Journal of Applied Physics (931405(158).

SUMARLIN I.W., LYNN J.W., CIIATTOPADHYAY T..

BARII.O S.N., ZHIGUNOV D.I.

Dispersion of the magnetic excitations of the Pr ions in Pi^CtiO.).PhysicuC(93SU5(MI).

5. Crystal and Magnetic StructuresSa - Crystallogruphy of Non-Magnetic Systems

ALEKSANDROVA I.P., PARLINSKY K.. CURRAT R.,VETTIER C., ECKOLD G.The resonance and neutron diffraction study of RbiZnBrj under

hydrostatic pressure.

Integrated Ferroeleclrics (93AL5I08).

BARUCHEL J., EPELBOIN Y., GASTALD] J., HAERTWIG J.,

KULDA J.. REJMANKOVA P., SCHLENKER M,, ZONTONE F.

First topographic results at the European Synchrotron Radiation Facility.

Physica Status Solidi (93BA5I30).

BAUMBACH G.T.. HOLY V., P1KTSCH U., GA1LHANOU M.

The influence of specular interface reflection on grazing incidence X-ray

diffraction and diffuse scattering from superlatlices.

PhysicaB(9?BA5l26).

BUETTNER H.G.. KEARLEY G.J.. HOWARD C.J.. FILLAUX F.

The crystal structure of the Ilot'maim clathrales : Ni(NH,hNi(CN)4.2C(,Dr,

and Zn(NH,)2(Ni(CN)4,2C(,lltl.

Acta Crystallographica (93BU5115).

FILHOL A.Organic conductors: The cryslallographic approach.

Organic conductors: Fundamentals and Applications. Series "Applied

Physics", Marcel Dekker, Inc. (93FI5092).

GERTEL II., BROKMKIER U.C., BUNGE H.J.. RITTKR C.

High temperature in situ texture measurements at the neutron powder

dil'fractometcrDIB.

Journal of Materials Sciences Letters (93GE514K).

VOGT T.. FITCH A.N.. COCKCROPT J.K.

The crystal and molecular structures of rhenium hcptafluoridc.

Science (93VO5153).

5b - Crystallography of Magnetic Systems

BONNET M., BOUCHERLE J.X.. GIVORD F.. LAPIERRE F..

LFJAY P., ODIN J.. MURANI Л.Р.. SCIIWEIZER J.. STUNAULT A.

Anomalous magnetic behaviour of cerium in CeiSn<j and Cc^Siiy.

two superstructures of CcSiiv

Journal of Magnetism and Magnetic Materials (93BO5114).

CHATTOPADHYAY T.. BROWN P.J.. ROESSL1 B.Disappearance of the three-dimensional magnetic ordering iJournal of Applied Physics |93CH5053|.

GARCIA-MATRKS E., C.ARCIA-MUNOZ J.I.., MARTINEZ J.L..RODRlfiUKX-CARVAJAL J.Magnetic properties of RifîaNiOj oxides.PhysicaB(U3GA5087).

HERNANDEZ-VELASCO J., SABZ-PUCHR R., RODRIGUEZ-CARVAJAI. J.. GARCIA-MATRRS F... MARTINEZ J.L.Magnetic properties of novel RiBitCnOj oxides (R = Pr, Nd, Ho).Journal of Compounds and Alloys (93HE50X6).

ISNARD ()., MIRAGI.1A S., GUIU.OT M., FRUCHART D.High field magneti/ation measurenients of SnbFe|7 , SmiFcpNj,SiibFe 1 7D5 iind Pr:Fe , 7. Pr:Fe , 7N , ,Journal of Applied Physics I'J.ilS? 1-171.

ISNARD ()., FRUCHART D.Magnetism in l-'e-hascd intrriielullics: relationships between localenvironments ami local m>. iclic moments.Journal of Alloys and Compounds (93IS5 1 54).

OULADDIAF В.. NEUMANN K.U., CRANGLF. J.. ZA YER N.K..ZIEBECK K.R.A.

A neutron diffraction study of the phase transition in PdiTiln.Journal of Physics : Condensed Matter (93OU506fil.

REEHL'IS M.. VOMHOF T.. JE1TSCHKO W.

The magnetic structure of UGbPi.Journal of Physics and Chemistry of Solids (93RE5 1 58).

REEHL'IS M.. ZEPPENFEI.D K.. JEITSCHKO W.. RESSOUCHE E.Magnetic structure of DyiCriCvJournal of Alloys and Compounds (93RE5I59».

TASSET F.Magnetic structures and neutron polariinctry.Proceedings of the Symposium in Memory of Remy Lemaire "Magnetismof Rare Earth Intermetallic Alloys". Laboratoire Louis Néel. Grenoble.France. JuK 2. 1993 <93TA5(>57|.

FRICK В., BUCHENAU U.

Boson peak and last relaxation process near the glass transitionin polystyrene.

Colloid & Polymer Science (Proceedings of the 28th EurophysicsConference on "Transitions in Oligomer and Polymer Systems". Ulm,

Germany, September 27 - October I. 1993) (93FR5085).

GYGAX F.N.. AMATO A.. ANDERSON I.S.. RUSH J.J.. SCHENCK A.

Study of u.+ localization and diffusion in Sc and ScH(,(,5.

Zcitschrift fuer physikalische Chemie (93GY 5135 ).

GYGAX F.N., AMATO A., SCHENCK A.. ANDERSON I.S.,RUSHJ.J..SOLTG.

ц + localization and tunneling in Se.

6th International Conference on Muon Spin Rotation / Relaxation /Resonance, Wailea, Mttui. Hawaii. May 1993 (93GY5136).

JANOTC.

Quasierystiils.Neutron ami Synchrotron Radiation for Condensed Matter Studies •Volume II: Applications to Solid State Physics and Chemistry(Lecture Notes for HERCULES). Editions de Physique and SpringerVerlag - (Eds. J. Baruehel, J.L. Hodeau, M.S. Lehmann, J.R. Regnard,C. SchlcnkcrHMLESU»).

MUTKA H.

Influence of delects and impurities on CDW systems.

"Advances in the Crystallographic and Microstructural Analysis

of Charge-Density Wave Modulated Crystals". Boswell F., Bennett C.

(Kluwcr Academic Publishers, Dordrecht) (93MU5075).

PREVEL В., DUPUY-PHILON J.. JAL J.F., LEGRAND J.F., CHIEUX P.

Structural relaxation in supercooled glass forming solutions: a neutron spin

echo study of LiCI. ft D2O.

Journal of Physics: Condensed Matter (93PR5I40).

SCHAEFER D.W., OLIVIER B.J.. ASCHLEY C.. BEAUCAGE G..

RICHTER D., FARAGO В., FRICK В.. FISCHER D.A.

Structure and topology of silica aerogels during dcnsification.

Journal of Non-Crystalline Solids (93SC51S6).

6. Liquids, Disordered Materialsand Metal PhysicsANDERSEN K.M.. STIRLING W G.. SCHERM R.. STUNAULT A..КАК I!.. GODFRIN H.. DIANOL'X A.J.Collective excitations in liquid 4He. I: Experiment and presentation of data.Journal of Physics: Condensed Matter (93AN5D55).

CHEVRIER J.. SL'CK J.-B.. LASJAUMAS J.C.. PF.RROUX M..CAPPONI J.J.Nonccjuilihnnm stale and lattice instability in supersaturated aluminumsilicon solid solutions.

Physical Review li (43CII5I4I I.

CHIEUX P.. DfPUY-PHII.ON J.. JAL J.-F.. MORKEI. C.. SUCK J.-B.Collective atomic dynamics in mixtures of liquid alkali metalsand molten alkali halides.Journal <>l Physics: Condensed Matter (93CH5M21.

FRICK В.. RICIITF.R D.. ZORN R.. FETTERS L.J.The fast relaxation process near the glass transition in amorphous polymerswith different microstructure.Journal of Non-Crystalline Solids (2nd International Discussion Meeting onRelaxations in Complex Systems. Alicante. Spain. June 28 - JuK 8. 19931(93FR5()«2l.

8. Biological Structures and DynamicsCHARVOLINJ.

Membrane in chlomplasts. a topnlogical approach to grana and frets.Biophysical Chemistry (93CH5062).

JEANTEUR D.. PATTUS F..TIMMINS P.A.

The membrane-bound form of the pore-forming domain of colicin A:

a neutron scattering study.

Journal of Molecular Biology (93JE5127).

LEHMANN M.S.

Neutron crystallography of biological molecules.

Neutron and Synchrotron Radiation for Condensed Matter Studies -

Volume III: Applications to Soft Condensed Matter and Biology

(Lecture Notes for HERCULES). Editions de Physique and SpringerVerlag - (Eds. J. Baruchel, J.L. Hodeau, M.S. Lehmann. J.R. k'egnard,

C. Schlenker) (93LE5099).

MAYR.Small-angle neutron scattering of biological macmmolccular complexes

consisting of proteins and nucleic acids.

Modern Aspects of Small Angle Scattering. NATO ASI Series (Proceedings

of the Conference held in Como, Italy, May 12-22.1993) (93MA5I57).

TIMMINS P.A.

Neutron scullcring in biology.

Proceedings of the Summer School on Neutron Scattering, August 15-21,1493. Zuoz. Switzerland (93T15059).

TIMMINS P.A.

Virus structure: contributions from X-ray synchrotronand neutron radiation.

Neutron and Synchrotron Radiation tor Condensed Mutter Studies -Volume HI: Applications to Soft Condensed Matter and Biology

(Lecture Notes for HERCULES). Editions de Physique and SpringerVerlag - (Eds. J. Baruchel, J.L. Hodeau, M.S. Lehmann, J.R. Regnard,C. Schlenker) (93LE5102).

9. Chemistry9a • Molecular Spcctroscopy, Surfaces and Mcsophases

DIANOUX A.J., SAUVAJOL J.L,. KNELLER G.R., SMITH J.C.

Dynamics of pristine and doped polyacctylene : a combined inelastic

neutron scattering and computer simulation analysis.

Journal of Non-Crystalline Solids (Proceedings of (he 2nd International

Discussion Meeting on Relaxations in Complex Systems, Alicante,

Spain. June 28 - July 8, 1493) (93D150SO).

EL BAGHDAD! A., GUILLAUME F.. BOYSEN H.,

DIANOUX A.J., CODDENS G.

Trunslaiional and rotational motions of n-ulkane molecules withinthe channels of urea inclusion compounds.

Proceedings of the International Conference "Quasielaslic Neutron

Scattering '93". Future Prospects on High-Resolution Inelastic Neutron

Scattering. San Sebastian. Spain. September 27-28. 1993 - World ScientificPublishing Co. (93BA5077).

FRICK В.. FETTERS L.J.

Methyl group dynamics in glassy polyisoprene - a neutron backscatteringinvestigation.

Macromolecules (93FRS08I ).

9b - Colloids and Polymer

BERRET J.F.. ROUX D.C.. PORTE G., LINDNER P.

Shear-induced isotropic-to-nematic phase transition in equilibrium

polymers. Europhysics Letters (93BE5112).

BOUE F.. LINDNER P.

Scmidilute polymer solutions under shear.

Europhysics Letters (93BO5111 ).

CHARVOLIN J.

Soft Condensed Matter: Introduction.

Neutron and Synchrotron Radiation for Condensed Matter Studies -

Volume III: Applications to Soft Condensed Matter and Biology(Lecture Notes for HERCULES). Editions dc Physique and SpringerVcrlag - (Eds. J. Baruchcl. J.L. Hodcau, M.S. Lehmann. J.R. Regnard.C. Schlenker) (93LE5106).

GUENET J.M., MENELLE A.. SCHAFFHAUSIÏR V., TERfiCII P.,THIERRY A.

Isotactic polystyrcnc/cis-decaline mixtures: phase diagramand molecular structures.

Colloid and Polymer Science (93OU5I43).

HANLEY H.J.M., STRATY G.C.. LINDNER P.

Partial scattered intensities from a binary suspension

of polystyrene and silica.

Langmuir (93HA5033).

LEGRANDJ.F.

Partially crystallized polymer systems.

Neutron and Synchrotron Radiation for Condensed Matter Studies -Volume HI: Applications to Soft Condensed Matter and Biology(Lecture Notes for HERCULES). Editions de Physique and SpringerVerlag - (Eds. J. Baruchcl. J.L. Hodeau. M.S. Lehmann, J.R. Regnard.C. Schlenker) (93LE5100).

LEGRANDJ.F.

Le PVDF et les copolymeres diirives : des polymères l'errocïeclriques."Initiation à la Chimie et a la Physico-Chimie Macromoliieiiliiire,Vol. 9 : Introduction aux propriétés électriques des polymèreset applications". Ed. Groupe Français des Polymères (93LE5151).

LI J.-C. HOWE L.D., BENHAM M.J., ROSS O.K..

STANLEY H.B.. IBEL K.

Small angle neutron scattering studies of the desorplion

and adsorption of water in porous vycor glass.

Physical Review В (93LI5149).

OLIVIER B.J., SCHAEFER D.W.. FRICK В., RICHTER D.,

FARAGO В.. ASHLEY C.S., KAMITAKAHARA W.A.

Low-energy dynamics of colloidal versus polymeric silica aerogel.

Transactions of the American Cryslallographic Association (Proceedings

of the Symposium on "The Structural Chemistry of Silicates", Toledo,

Ohio, USA, July 22-24, 1991 ) (93OL5I55).

TERECH P.. RODRIGUEZ V.

Surfactant aggregation in organic solvents: physical gelsand "living polymers".

Progress in Colloid and Interface Science (93TE5I44).

TERECH P.

Agrégation de surfactants en milieu organique : gels physiqueset polymères vivants.

Images de la Recherche. Numéro spécial : Systèmes MoléculairesOrganisés (93TE5145).

VERKHOVSKAYA K.A., FRIDKIN V.M., BUNE A.V.. TATIKOLOVA.S., LEGRANDJ.F.

The fluorescence of a dye sensitized ferroelectric polymerin an external electric Held.

Journal of Applied Physics (93VE5I50).

FARAGO B.

Dynamics and diffusion in macromolcculcs, colloi'ds and microcmulsions.Neutron and Synchrotron Radiation for Condensed Matter Studies -Volume III: Applications to Soft Condensed Matter and Biology(Lecture Notes for HERCULES). Editions de Physique and SpringerVeriag - (Eds. J. Baruchel, J.L. Hodeau, M.S. Lehmann. J.R. Regnard,C. Schlenker) (93LE5101).

AcknowledgementThe Scientific Secretary, Bruno Dorner, editor of this report,

wishes to thank all those who have contributed.

Layout and typesetting by Icira

Cover layout and printing by Technic Color

Photography byJ.L. Baudet (ILL). S. Claisie (ILL), .1. Italia (ILL).

Other publications available

- Guide to Neutron Research Facilities, Edition 1988/89

-General Information and Regulations, Edition 1990.

The Scientific SecretaryInstitut Max von Laue - Paul Langevin

BPI5638042 Grenoble Cedex 9

FranceTelephone: 76 20 72 93 - Telefax: 76 48 39 06 - Telex: 320621

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