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NuclearPhysics

News

Vol. 15, No. 3, 2005, Nuclear Physics News 1

Nuclear Physics News is published on behalf of theNuclear Physics European Collaboration Committee(NuPECC), an Expert Committee of the EuropeanScience Foundation, with colleagues from Europe,America, and Asia.

Volume 15/No. 3

Editor: Gabriele-Elisabeth Kömer

Editorial BoardJ. D’Auria, Vancouver W. Kutschera, ViennaR. F. Casten, Yale M. Leino, JyväskyläT. W. Donnelly, MIT Cambridge R. Lovas, DebrecenA. Eiró, Lisbon S. Nagamiya, TsukubaM. Huyse, Leuven (Chairman) C. Trautmann, Darmstadt

Editorial Office: Physikdepartment, E12, Technische Universitat München, 85748 Garching, Germany, Tel: +49 89 2891 2293, +49 172 89 15011, Fax: +49 89 2891 2298,

E-mail: [email protected]

CorrespondentsArgentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Oberhummer, Vienna; Belgium:C. Angulo, Lauvain-la-Neuve; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou,TRIUMF; K, Sharma, Manitobu; C. Svensson, Guelph: China: W. Zhan, Lanzhou; Croatia: R. Calpar, Zagreb; CzechRepublic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Årnus; Finland: M. Leino,Jyväskylä; France: G. De France, GANIL Caen; B. Blank, Bordeaux; M Guidal, IPN Orsay; Germany: K. D. Gross, GSIDarmstadi; K. Kilian Jülich; K. Lieb, Göttingen; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen;India: D. K. Avasthi, New Delhi; Israel: N. Auerbach, Tel Aviv; Italy: E. Vercellin, Torino; M. Ripani, Genova; L. Corradi,Legnaro; D. Vinciguerra, Catania; Japan: T. Motobayashi, RIKEN; H. Toki, Osaka; Malta: G. Buttigieg, Kalkara;Mexico: J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen,Bergen; Poland: T. Czosnyka, Warsaw; Portugal: M. Fernanda Silva, Sacavém; Romania: A. Raduta, Bucharest; Russia:Yu. Novikov, St. Petersburg; Spain: B. Rubio, Valencia; Sweden: P.-E. Tegner, Stockholm; Switzerland: C. Petitjean,PSI Villigen; United Kingdom: B. F. Fulton, York; D. Branford, Edinburgh; USA: R. Janssens, Argonne; Ch. E. Reece,Jefferson Lab; B. Jacak, Stony Brook; B. Sherrill, Michigan State Univ.; H. G. Ritter, Lawrence Berkeley Laboratory;S. E. Vigdor, Indiana Univ.; G. Miller, Seattle.

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GNPN Ediboard.fm Thursday, August 11, 2005 11:59 AM

NuclearPhysics

News

1 Nuclear Physics News, Vol. 15, No. 3, 2005

Volume 15/No. 3

Contents

Editorial............................................................................................................................................................. 00

Laboratory PortraitThe Saclay Nuclear Physics Division

by Nicolas Alamanos ..................................................................................................................................... 00

Feature ArticlesA Relativistic Symmetry in Nuclei

by Joseph N. Ginocchio................................................................................................................................. 00

Exploding Stars, Neutrinos, and Nucleosynthesisby Gail McLaughlin....................................................................................................................................... 00

Facilities and MethodsHigh-Resolution Gamma-Ray Spectroscopy at TRIUMF-ISAC

by Greg Hackman.......................................................................................................................................... 00

Radioactive Ion Beam Facility in Brazil (RIBRAS)by R. Lichtenthäler, A. Lépine-Szily, V. Guimarães, and M.S. Hussein........................................................ 00

BEN@ECT*: The New 1Tflop/s Computing Facility at The European Centre for Theoretical Studies in Nuclear Physics and Related Areas

by Pierfrancesco Zuccato .............................................................................................................................. 00

Recent Achievements in Multinucleon Transfer Reaction Studies at LNLby Lorenzo Corradi and Giovanni Pollarolo................................................................................................................ 00

Meeting ReportsAtomic Nuclei at the Extreme Values of Temperature, Spin, and Isospin, XXXIX Zakopane School of Physics, 31 August–5 September 2004, Zakopane, Poland

by Angela Bracco ........................................................................................................................................................... 00

Symposium on “Atomic High-Precision Mass Spectrometry”by Klaus Blaum and Lutz Schweikhard

Report on the 15th Panhellenic Symposium on Nuclear Physicsby Georgios A. Lalazissis

News and Views ................................................................................................................................................ 00

Calendar ............................................................................................................................................................ 00

GNPN Contents.fm Thursday, August 11, 2005 3:02 PM

editorial


The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

The need for Ion Accelerators in Non-Nuclear Physics Fields

When ion implantation started toreplace diffusion as a means for dop-ing semiconductors, the market leaderhesitated too long to install the newtechnology and was outrun by others.Admittedly, hardly anyone at that timehad envisioned the huge impact ionimplantation would have on the semi-conductor industry, finally becominga key technology in complex produc-tion lines. This success is directlylinked to the comprehensive under-standing of ion–matter interaction pro-cesses achieved at accelerators providedby the nuclear physics community.Theoretical models and simulationcodes (such as TRIM) predicting theeffect of elastic collision cascadeswere indispensable for optimizingproduction performances and develop-ing ion beam technology in the low-energy regime (up to several hundredkeV per nucleon). Many standardtechniques, such as SIMS, PIXE,RBS, ERDA, and AMS are nowadaysin regular use, mainly for materialsanalysis, with the general trend tosmaller beam dimensions includingfocused ion beams for producingnanostructures.

The continuous drive of thenuclear physics community to higherenergies at larger accelerator facili-ties offered new possibilities forresearch activities in application-oriented fields. In contrast to low-energy ions, ion-matter interactionwith beams above about 1–3 MeV pernucleon are dominated by electronicprocesses with a huge energy deposition

along the ion trajectory. There are noother means by which similar high-energy densities can be placed thatdeep in the bulk of materials. Thelarge ion range in combination withthe small track diameter of a fewnanometers play a key role fornumerous applications. Research per-formed at large accelerator facilities,mainly in Europe but with increasingintensity also in Japan, China, andIndia, is significantly improving theunderstanding of basic electronicexcitation processes, track formation,and ion-induced degradation, and thetailoring of materials properties. Thenumber of different topics addressedis enormous, ranging from studies ofmaterials response to extreme radia-tion conditions (reactor material,nuclear waste storage), dating of geo-logical minerals, fabrication of nano-objects, simulation testing of cosmicrays on electronic devices for space,to radiation effects on biologicalcells. Extensive basic research in thisfield has been essential for the devel-opment of hadron tumor-therapy,which is now emerging with severaldedicated facilities in the construc-tion or planning phase.

Considering the broad potential ofswift heavy ions, the closing of the ionbeam facility (Ionenstrahllabor ISL) atthe Hahn-Meitner Institute in Berlin,announced for the end of 2006, causeda shock. After termination of thenuclear physics program, this machinehas been exclusively devoted to basicmaterials research and applied activities

including commercial membrane pro-duction and proton-therapy for eyetumors. The versatility and the high-duty cycle of the ISL machine providemost suitable beam conditions forirradiation experiments in materialsscience. The decision to shut downcannot be understood on the basis ofscientific arguments because a recentevaluation rated the performedresearch as excellent.

Why is successful exploitation ofenergetic ion beams with spin-offapplications in many disciplines notsufficient to justify the continuedoperation of a dedicated facility? Canthese activities only coexist withnuclear physics? Even more impor-tant, what will happen if the perma-nent striving for higher energies innuclear and particle physics contin-ues, resulting in shutting down moreand more smaller accelerators? Howcan the ion-beam community respondto additional tasks linked, for exam-ple, to the future fusion reactorproject, ITER, or to incineration andtransmutation of reactor waste inaccelerator-driven reactor systems?At present, the beamtime schedule atlarge facilities is complex and usuallyoverbooked. Experimental accessinvolves slow proposal evaluationprocesses, a situation which is cer-tainly not adequate for materialsscience, in particular if industrialpartners are involved. A commonEuropean effort may help to improveaccess conditions by interconnectinghigh-energy accelerators of, for

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example, GANIL, GSI, Legnaro,Munich, and Orsay to a virtual facilityand setting up special arrangementssuch as beam-quota allocations andindependent proposal and programcommittees. In any case, the risk thatessential needs of the ion-beam com-munity in applied disciplines will notbe covered adequately in the futurehas to be seen as very large.

CHRISTINA TRAUTMANN

GSI Darmstadt, Germany

WALTER ASSMANN

LMU MunichCHRISTINA TRAUTMANN

GSI, DarmstadtMARCEL TOULEMONDE

CIRIL, Caen


The Saclay Nuclear Physics Division

Query SheetQ1 AU: provide citation for figure 7

laboratory portrait


The Saclay Nuclear Physics Division

The Nuclear Physics Division(Service de Physique Nucléaire, SPhN)of DAPNIA at Saclay in France is partof the fundamental research divisionsof the CEA (Commissariat à l’EnergieAtomique). Its programs cover a broadrange of topics in Nuclear Physics fromlow to high energies. They include thestudy of the structure and dynamics ofthe nucleus, the structure of thenucleon, and the search for phase tran-sitions of nuclear matter. SPhN alsocontributes to measurements and mod-eling of specific nuclear reactionsrelated to nuclear waste transmutation.Furthermore, physicists apply theirknowledge, competence, and techniquesto the development of innovativenuclear energy cycles, to the produc-tion of neutron and radioactive beamsand to the decommissioning of nuclearinstallations. The research activitiestake place within strong national andinternational collaborations involvingthe academic world and enabling theselection and training of high-qualitystudents and post-doctoral researchers.

The Structure of the Nucleus The objective of experiments in

this area is to test and improve thedescriptive and predictive power ofnuclear structure models in the mostextreme conditions with regards tonuclear isospin, angular momentum,mass, and temperature. Most of theseexperiments concern very unstablenuclei for which new phenomena suchas very diffuse nuclear surfaces, clus-tering, low-lying resonances, or newmagic shells appear that are not pre-dicted by present models. The isospindependence of the effective nucleon-nucleon force is a key ingredient ofthe models. One may expect that,

along with other parameters of theeffective force, such as the spin-orbitcoupling or the pairing term, it willneed to be readjusted for nuclei farfrom stability.

SPhN is involved in the study ofthe structure of light exotic nucleisuch as 6–8He, 10–11C, 27Ne and in thestudy of shape coexistence in Kr iso-topes. The experiments are performedat GANIL with beams delivered bythe SPIRAL or SISSI facilities. It isalso involved in experiments atJyväskylä (Finland) to obtain informa-tion on the spectroscopy of transfer-mium nuclei and especially on thestructure of 251Md. Near-barrier andsub-barrier fusion of light unstablenuclei and their respective stable iso-topes with 238U targets are studied atLouvain La Neuve (Belgium). Amongthe most significant experimentalresults, one can mention the remarkablesensitivity of inelastic scattering to thehalo structure of 6He, studies on thestructure of 8He (Figure 1), the firstexperimental evidence for a shapeisomer in N=Z nuclei (72Kr) supportingthe predicted scenario of prolate-oblateshape coexistence in this mass regionand, by combining conversion-elec-tron and gamma-ray spectroscopy, thefirst study of the structure of an oddtransfermium nucleus 251Md (Figure 2).

The experiments were realizedwith experimental devices constructedwithin the framework of national andinternational collaborations and withthe participation of DAPNIA technicaldivisions. This encompasses participa-tion in the construction of the siliconstrip detector array MUST, of the seg-mented clover Ge detector EXOGAM,of the focal plane detection system ofthe VAMOS spectrometer and of the

target chamber with a rotating targetsystem dedicated to the study of thestructure and production of heavy andsuper-heavy elements. SPhN is nowparticipating in the development ofexperimental devices designed tomeasure with better efficiency, energyresolution, and granularity recoil par-ticles (MUST2) and gamma rays(AGATA) produced in reactionsinduced by radioactive beams.

Nuclear structure physicists unani-mously support the SPIRAL2 project,which aims to accelerate from 2009radioactive beams produced by fissionof uranium, and which will give accessto beams of heavier nuclei than thoseobtained from the current SPIRAL facil-ity. Medium- and long-range plansencompass participation in the new GSIproject R3B and in elaborating the phys-ics case for the European EURISOLproject as well as in participating in itsdesign and construction.

Nuclear Phase Transitions Heavy ion collisions offer the pos-

sibility to create nuclear matter in thelaboratory under extreme conditionsof pressure and temperature. The pur-pose of our activities in this domain istwofold: the study of the liquid–gasphase transition in nuclei at relativelylow incident energies and the searchfor the quark-gluon plasma at veryhigh energies.

At relatively low incident energies,SPhN is involved in studies of thedynamics of heavy-ion collisions thataim at obtaining information on theequation of state of nuclear matter andconcomitantly on the liquid–gas phasetransition. This is an ingredient ofnuclear dynamics governing stellar pro-cesses such as supernova explosions.


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The main experimental tool for thesestudies is the 4π multiparticle INDRAdetector, built with strong contribu-tions from DAPNIA’s technical divi-sions. One of the quantities of interestin these collisions is the excitationenergy of the nuclei formed beforeany particle emission. An outstandingresult in this domain is the direct mea-surement of the thermal excitationenergy of the primary fragments pro-duced in central collisions between 32and 50MeV/A. The experimental resultsare well reproduced by statistical multi-fragmentation models. These finding,combined with other experimentalsignatures, allow a better understand-ing of nuclear matter dynamics below5MeV/A excitation energy.

At high temperatures and/or den-sities, QCD predicts a new form ofmatter, consisting of an extendedvolume of deconfined quarks, anti-quarks, and gluons called the quark-gluon plasma (QGP). The aim hereis to study the properties of thisplasma, which is thought to haveexisted a few microseconds after theBig Bang.

SPhN participates in this search.Among the signatures of the QGP oneof the most promising is the colorscreening of heavy resonances (J/ψ andY) formed by pairs of heavy quarksand antiquarks. We study these reso-nances through their decay into pairsof muons in two experiments: PHENIXwith the accelerator RHIC at (BNL)and ALICE at the LHC (CERN).These two experiments use a dimuonspectrometer for the detection of reso-nances. SPhN has contributed to theelectronics of one of the dimuon armsof the PHENIX experiment and isactively participating in the constructionof the dimuon arm for the ALICEexperiment (Figure 3).

Figure 1. To investigate the structure of exotic nuclei with direct reactionsin inverse kinematics, the MUST detector has been developed(collaboration IPN Orsay, SPhN and SPN Bruyères le Chatel). A typicalexperimental arrangement is presented (top). In particular, it was usedwith the Spiral 8He beam at 15.6 MeV/nucleon impinging on proton target.A complete kinematical reconstruction of the induced direct reactions isachieved via the identification of the light recoiling particle in the MUSTarray in coincidence with the heavy reaction partner detected in a wall ofplastic scintillator. Two beam tracking detectors, CATS developed byDAPNIA, are used to reconstruct event by event the trajectory of theincident particles. The energy versus scattering angle spectrum of theparticles detected in MUST is shown (bottom). The kinematical lociindicate the elastic and inelastic scattering to the unbound first 2+ excitedstate of 8He (3.6 MeV) and the one- and two-nucleon transfer reactions8He(p, d), 8He(p, t).


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PHENIX is currently taking data atRHIC at nucleon-nucleon collisionenergy of 200 GeV. Results on J/ψproduction in Au-Au collisions will be

available soon. A striking resultobtained recently is the jet suppressionobserved at large transverse momen-tum. Indeed, data from the PHENIX

detector show that the production rateof high-transverse momentum pions issuppressed in Au+Au collisions ascompared to p+p or d+Au collisions.This result is compatible with suppres-sion in a dense colored medium andcould be the signature for the QGPformation.

ALICE is an experiment at theLHC (CERN), which is in the courseof preparation and that will take itsfirst data in 2008 at an energy about30 times higher than that of PHENIX(5.5 TeV).

It is anticipated that the existenceof the QGP will be firmly establishedat RHIC and its detailed propertiesstudied at ALICE/LHC in the forth-coming years.

The Structure of the Nucleon SPhN is involved in two exp-

erimental programs both using elec-tromagnetic probes, one to obtaininformation on the spin carried by thegluons in the proton (COMPASS atCERN) and the other to extractinformation on generalized parton dis-tributions by means of deeply virtualCompton scattering (CLAS at JLAB).

The contributions of quarks (∆Σ)and gluons (∆G) to the spin of thenucleon are accessible by using apolarized lepton beam and a polarizednucleon target. Recent experiments atCERN (SMC) and at SLAC, withstrong participation by SPhN, haveestablished that the contribution of thequarks to the spin of the nucleon issmall. These results have been com-plemented by the HERMES experi-ment at DESY and it is now widelyaccepted that the quark intrinsic spin con-tributes only a small fraction (20–30%) tothe total nucleon spin. These results agreewith recent QCD calculations.

Figure 2. Top: Gamma-ray spectrum obtained in the Coulomb excitation of a4.5 MeV/u 74Kr beam from SPIRAL taken with the EXOGAM spectrometer atGANIL. The intensities observed for the different states allow extracting staticand transitioning quadrupole moments and confirm the supposed shape coexistencescenario. Bottom: First observation of a rotational band in an odd-massTransfermium nucleus. The spectrum was taken with the Jurogam spectrometerat the University of Jyväskylä and obtained by tagging the gamma rays with thealpha decay of 251Md in the focal plane of the RITU gas-filled separator.


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The main goal of the COMPASSexperiment is the measurement of thegluon polarisation in the nucleon. DAP-NIA has contributed to the COMPASSspectrometer by developing and building12 micro-strip “micromegas” detectors(40×40cm2) (Figure 4) and 24 driftchambers (120×120cm2). These detec-tors are placed in the zone of high particleflux, immediately behind the target. Datataken in 2002 and 2003 have been ana-lyzed. These data already provide com-petitive statistics for numerous channels:measurement of g1 (better than SMC atsmall x), semi-inclusive scattering(already comparable to Hermes), coeffi-cients of the ρ meson spin density matrix,polarisation of the ∆ (as good asNOMAD) and Λ− (much better thanNOMAD). However, the main challengeremains the determination of the gluonpolarization ∆G/G. At the recent interna-tional conferences SPIN04 in Trieste andBARYONS04 at Palaiseau, the firstresults on ∆G/G from high transversemomentum hadron pairs were presented.

QCD also provides predictions forthe transversity, which is the probabil-ity of measuring a quark with a spinorientation parallel to that of thenucleon spin when this is perpendicu-lar to the incident beam. Transversityalso manifests itself by a structurefunction that is a new aspect of thequark dynamics in the nucleon. In theyears to come the COMPASS experi-ment will measure the transversity andbring information in this area that isessentially untouched experimentally.

The generalized parton distribu-tions (GPD) allow an exploration ofthe three-dimensional structure ofnucleons in terms of partons. Theinnovative aspect of these quantities istheir sensitivity to correlationsbetween partons, allowing for exam-ple, to connect them to the total angu-lar momentum carried by the quarks

or the gluons. Experimentally, the GPDsare accessible through exclusive hardreactions. Among these, the simplestprocess is deeply virtual Comptonscattering (DVCS), ep → epγ. One ofthe first DVCS measurements waspublished by the CLAS collaborationat JLAB in 2002. Physicists fromSPhN have contributed to the mea-surement of the spin asymmetry forthe DVCS process at a beam energy of4.2 GeV. New experiments are inpreparation at JLAB using experimen-tal equipment under construction atSaclay (Figure 5). The first goal ofthese exploratory measurements is tovalidate the theoretical connectionbetween DVCS and GPDs.

In parallel with these experimen-tal activities, the three theorists ofSPhN have focused their activities onthe structure of the nucleon andbaryon resonances. Subjects that areparticularly studied are the GPDs, theform-factors of the nucleon, and reac-tions for the electromagnetic produc-tion of photons and mesons indifferent kinematic regimes.

Today, there are good prospects forpowerful electron facilities in theUnited States in particular at JLAB. Itis therefore important to continue ourinvestigations at JLAB in which,thanks to a future increase of the beamenergy to 12GeV, measurements of theGPDs will be carried out in a wider

Figure 3. Large tracking stations are necessary to cover the solid angle of theALICE dimuon spectrometer. The largest ones are visible on the picture, withstation 3 located inside the dipole magnet and stations 4 and 5 downstreamfrom it. They consist of cathode pad chambers arranged in slats on carbonfibber supports on both sides of the beam pipe and shielding. Station 3 is shownat its working position. Only the right halves of stations 4 and 5 are shown attheir working positions. Dapnia/SPhN physicists and Dapnia technical divisionshave been heavily involved in their design and prototype commissioning.Dapnia is responsible for building one fourth of them and for integrating all ofthem in the muon spectrometer.


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kinematic range from 2010 onward. Inparallel, a team from SPhN is studyingthe possibility of measuring DVCSwith the COMPASS spectrometer atCERN starting also in 2010 in a com-plementary kinematical region.

Physics for Nuclear Energy In the years to come fast neutron

reactors will enable the exploitation ofthe considerable resources offered byuranium 238U as well as by an eventual232Th fuel cycle. Nevertheless, the

Figure 4. The COMPASS experiment at CERN has a broad physics programfocused on the study of the spin structure of the nucleon and on hadronspectroscopy. The two-stage spectrometer is designed for high particle rates andhigh resolution tracking. The photo shows one of the Micromegas “doublets”consisting in two microstrip detectors oriented perpendicularly, with 1024strips each covering a 40 × 40 cm2 active area (top). Data taking has started in2002, and will last at least until 2010. The first COMPASS preliminary resulton the gluon polarization ∆G/G, measured at a momentum fraction of the gluonxg = 0.13 has been obtained from high pT hadron pair data taken in 2002 and2003. It is compared to HERMES and SMC published results and to theoreticalpredictions obtained from fits to polarized deep inelastic data (bottom).

Figure 5. The CLAS/DVCSexperiment, to run in the spring of2005 at Jefferson Lab, willinvestigate over a large kinematicaldomain the applicability of the newconcept of Generalized PartonDistributions (GPD). A group ofSPhN physicists is part of the leadingeffort to assemble and run thisexperiment. A forward photoncalorimeter is being added in themiddle of the CLAS spectrometer, andDAPNIA provides the lasermonitoring for the 424 lead-tungstatecrystals. The necessary magneticshield for this calorimeter is asuperconducting two-coil solenoid(this figure), entirely built at DAPNIAwith an original cryogenic design,together with its controls and safetysystem. This is to date the largestequipment to be inserted withinCLAS.


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management of nuclear waste is anessential condition for the acceptanceof nuclear energy by society. In orderto progress in these areas and studynew means of producing nuclear energy,the neutron production through spallationprocess should be carefully studied andprecisely modeled. New sets of neutroninduced cross-sections are also neededfor many isotopes (especially thosepresent in waste) under various types ofreactor neutron fluxes. Our activities inthis domain are focused along threemajor lines: spallation studies, neutroncross-section measurements, and applica-tion-oriented modeling.

The goal of the spallation studiesis to achieve a complete understandingof spallation reactions with experi-ments covering a wide range of chan-nels. An SPhN group is participatingin spallation residue cross-sectionmeasurements at the relativistic heavyion facility of GSI (Darmstadt, Germany).A new experimental program is nowunder development (SPALLADIN)with the aim of performing moreexclusive spallation measurements bymeasuring spallation residues and evap-orated light particles in coincidence inorder to obtain information on the de-excitation stage of the reaction.

These experimental studies arecomplemented by theoretical develop-ment of high-energy spallation models(INCL4). These models, once vali-dated with a wide set of experimentaldata, are incorporated in high-energytransport codes such as LAHET3 orMCNPX and used to evaluate quanti-ties relevant to ADS design (Figure 6).It is foreseen that these studies will becontinued at the planned R3B relativ-istic heavy ion facility at GSI andwithin the framework of the NUSTARcollaboration.

In recent years, high-resolutionneutron-induced reaction cross-section

measurements have gained muchinterest due to the development ofnew activities related to nuclearenergy, such as the transmutation ofnuclear waste, the thorium-basednuclear fuel cycle, and ADS. These

new applications have triggered arenewed interest in neutron-nucleusreactions, in particular for isotopesand energy regions that are essentialfor the development and design ofthese concepts.

Figure 6. Mass distribution at several energies (top) and examples of isotopicdistributions at 1 GeV (bottom) of spallation residues produced in p+Fereactions measured using the reverse kinematics technique with the FragmentSeparator at GSI (collaboration SPhN – GSI – IN2P3 – Santiago deCompostella University). The experimental results are compared withcalculations using the Intra-nuclear Cascade model, INCL4, developed by thegroup in collaboration with the University of Liège, followed by two differentde-excitation models: the solid line is obtained with a standard evaporationwhereas the dashed line comes from a de-excitation code in which theproduction of light fragments originates from an asymmetrical fission modecompeting with classical evaporation. These results have been used to computethe impurity production in an Accelerator-Driven System window. Recoilvelocities have also been measured and allow assessing of damage due to atomdisplacements in such a window.


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SPhN has been involved from thebeginning in the construction of thenew time-of-flight facility nToF at

CERN. The strength of nToF lies in itsvery high instantaneous neutron fluxmaking the nToF facility particularly

suitable for measurements with a lowsignal-to-background ratio, as in thecase of radioactive or low mass sam-ples. SPhN is also involved in the neu-tron time-of-flight facility Gelina atGeel for carrying out both neutron cap-ture and transmission measurements.

In addition to the energy-dependentcross-section measurements, integralneutron-induced cross-sections areinvestigated by SPhN groups withinthe Mini-Inca project. This projectaims at determining experimentallythe optimal conditions for the trans-mutation of minor actinides in high-intensity, highly thermalized neutronfluxes.

Furthermore, SPhN is involved inthe measurement of neutron flux andactinide incineration rates inside the liq-uid lead-bismuth spallation target withinthe European MEGAPIE experiment(PSI, Switzerland). The MEGAPIEproject is the first experimental demon-stration of a 1MW liquid Pb-Bi spalla-tion target coupled to a high intensity(1.5mA) proton accelerator. This exper-iment will take place in 2006.

In parallel with the aforemen-tioned experimental activities, somefundamental and applied modelingactivities have been developed. Thisexpertise was developed to simulateand characterize neutron fluxes insidethe experimental Mini-Inca channels.It is now applied to calculations ofinnovative nuclear systems for nuclearwaste transmutation, intensive neutronsources based on spallation and photo-nuclear reactions, radioactive nuclearbeam production scenarios, character-ization of nuclear waste barrels,production of neutron-rich fissionfragments, and so on, in close cooper-ation with the LANL (U.S.).

These modeling tools are basedon a Monte Carlo technique allow-ing realistic geometry and material

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Figure 7. The n_TOF collaboration has recently built and exploited a newneutron time-of-flight facility at CERN in the frame of a shared cost RTD actionof the Fifth EU Framework Program. Since the final commissioning, a scientificprogram of measurements of neutron capture and fission cross-sections ofactinides, long-lived fission fragments and other isotopes relevant for nucleartechnology and nuclear astrophysics, has been scheduled in a first phase from2001 to 2004. The figure shows an example of the count rate spectrum of the232Th(n,γ) capture cross-section experiment at n_TOF at CERN, measured withneutron insensitive deutered benzene gamma-ray detectors. The program for asecond phase of measurements at CERN is currently in preparation.

Q1


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specifications in 3-D. When avail-able, the evaluated data libraries areused for multiparticle–nucleus inter-actions and transport calculations.Otherwise recent nuclear models areapplied to simulate different processesof interest including time-dependentevolution of nuclear fuel and/or irra-diation/production targets. Theseactivities serve as direct evidence ofthe link between knowledge of fun-damental nuclear physics and soci-ety-related problems.

This expertise led us to undertakemodeling related to the decommis-sioning of nuclear installations suchas particle accelerators and researchor industrial nuclear reactors, in col-laboration with DAPNIA/SDA. Weexpect these activities to be pursuedin the future within the framework ofcollaboration with the valorisationDAPNIA/cell. Finally, among emerg-ing activities we would like to quoteparticipation in Monte Carlo simula-tions of emission tomography for

medical diagnostic and treatmentpurposes.

The Service de Physique Nucléaireis part of the national basic researchcommunity and contributes to theexcellence of French research whileactively participating in the funda-mental missions of the Commissar-iat à l’énergie atomique.

NICOLAS ALAMANOS

Saclay


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A Relativistic Symmetry in Nuclei

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A Relativistic Symmetry in Nuclei

JOSEPH N. GINOCCHIO Theoretical Division, Los Alamos National Laboratory Los Alamos, NM 87545, USA

Introduction More than thirty years ago it was observed that certain

quantum energy levels in atomic nuclei were almost degen-erate in energy [1]. The states that are almost degenerate(quasi-degenerate) have different radial quantum numbersand different orbital angular momenta, features that madethe reason for their degeneracy difficult to penetrate.

The dynamics of neutrons and protons in nuclei havebeen successfully treated non-relativistically. Therefore ithas come as a surprise that this quasi-degeneracy of quan-tum states in heavy nuclei, which has eluded understandingfor about thirty years, can be explained by a relativisticsymmetry [2].

The Nuclear Shell Model Atomic nuclei are well described by nucleons moving in

a non-relativistic mean field with residual interactions thatinduce correlations between the nucleons. The dynamics of thenucleons in the orbits are described by the non-relativisticSchrödinger equation. For spherical nuclei the quantumnumbers of the orbits in the mean field are the radial quan-tum number, n, the orbital angular momentum, l, and thetotal angular momentum, j, which is the sum of the orbitalangular momentum and the spin; (n, l, j) for short. Theorbits that are quasi-degenerate in energy are (1, 0,1/2) and(0, 2, 3/2), (1, 1, 3/2) and (0, 3, 5/2), and so on. That is, theorbit with (n, l, j = l + 1/2) will be quasi-degenerate with theorbit (n − 1, l + 2, j = l + 3/2); that is the radial quantum num-bers will differ by one unit, the orbital angular momentawill differ by two units, and the total angular momenta byone unit.

For deformed nuclei the orbits that are quasi-degeneratehave angular momentum projection along the symmetryaxis differing by two units and total angular momentumprojection differing by one unit.

The Dirac Hamiltonian The Dirac equation, not the Schrödinger equation, must

be used to describe the relativistic dynamics of nucleonsmoving in a relativistic mean field. In the limit that the rela-tivistic mean field is small compared to the kinetic energy,

the non-relativistic limit, then the Schrödinger equationwill be a good approximation to the Dirac equation.

The Dirac equation has positive energy eigenfunctionsand negative energy eigenfunctions. The former are the eigen-functions of the particles and the latter are the eigenfunctionsof the anti-particles. A Dirac eigenfunction will then havetwice as many components as a Schrödinger eigenfunction. Inthe non-relativistic limit, the “upper” component of the posi-tive energy eigenfunctions will become the Schrödingereigenfunctions for the particles and the “lower” componentwill become vanishingly small, whereas the “lower” compo-nent of the negative energy eigenfunctions will become theSchrödinger eigenfunctions for the anti-particles and the“upper” component will become vanishingly small.

Likewise, in the Dirac equation two types of potentialsare possible, one a relativistic scalar and one a relativisticvector. The sum of the two potentials dominate the dynamicsof the particles whereas the difference of the two dominatethe dynamics of the anti-particles.

Symmetries of the Dirac Hamiltonian When the scalar potential and vector potential are equal

the Dirac Hamiltoian has spin symmetry. This means thatthe eigenfunctions that differ in the orientation of the spinwill be degenerate in energy. That is, the orbits (n, l,j = l + 1/2) and (n, l, j = l − 1/2) will have the same energy.These states are spin doublets because the energy does notdepend on the orientation of the spin. This symmetryoccurs in hadrons [3].

When the scalar potential is equal to the vector poten-tial, but opposite in sign, there is another symmetry of theDirac equation. This symmetry is called pseudospin sym-metry. The states that are degenerate have exactly the radialquantum numbers and orbital angular momenta of thequasi-degenerate states that have been observed in nucleiand are pseudospin doublets.

Relativistic Mean Field Relativistic models of nuclei include nuclear field theories

with nucleons interacting by the exchange of mesons on theone hand and nucleons interacting with relativistic interactions.


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These models are difficult to solve exactly but have beensolved in the relativistic mean field approximation, whichreduces to a Dirac Hamiltonian with the scalar and vectorpotentials determined self-consistently [4]. The resultingscalar and vector potentials are opposite in sign andapproximately equal in magnitude. Thus the symmetry,which was observed in the nuclear states more than thirtyyears ago, is pseudospin symmetry, a symmetry of theDirac Hamiltonian.

Predictions of Pseudospin Symmetry

Amplitudes One of the predictions of this pseudospin symmetry is

that the spatial amplitudes of the lower components for thetwo states in the degenerate doublets should be equal in mag-nitude. We have tested this condition by examining the loweramplitudes of the Dirac eigenfunctions determined in relativ-istic mean field calculations of nuclear spectra using realisticvector and scalar potentials [5]. In Figure 1 we show anexample of the amplitudes of the lower components of twostates of a pseudospin doublet in in the spherical nucleus

208Pb. in Figure 1a is the upper amplitude, g(r), for the (n= 1,l= 0, j= 1/2) state (solid line) and the (n=0, l =2, j =3/2) state(dashed line). These radial amplitudes have very different inshapes. However, the lower amplitudes, f(r), are almost iden-tical as seen in Figure 1b. In Figure 1c is the upper ampli-tude, g(r), for the (n=2, l= 0, j=1/2) state (solid line) and the(n=1, l = 2, j= 3/2) state (dashed line). Again these radialamplitudes have very different shapes. However, the loweramplitudes, f(r), are almost identical, as seen in Figure 1d. Asthe radial quantum number increases, the lower amplitudesbecome more similar, implying that pseudospin conservationimproves as the binding energy decreases,

Pseudospin symmetry also imposes conditions on the upperamplitudes but these are more complicated, involving differen-tial equations between the amplitudes. However, these condi-tions are approximately satisfied as well and improve as thebinding energy decreases [6] just like the lower amplitudes.

A survey of other states in both deformed and sphericalnuclei for pseudospin symmetry in both upper and lowercomponents show that pseudospin symmetry is approximatelyconserved and the conservation increases as the bindingenergy decreases [7].

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Figure 1. The upper amplitudes, g(r), and lower amplitudes, f(r), versus the radius r.

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Magnetic Dipole and Gamow Teller Transitions Magnetic dipole transitions between pseudospin doublets

are forbidden non-relativistically because the states in the dou-blets have angular momentum differing by two units and thedipole can only change the angular momentum by at most oneunit. However, these transitions are allowed relativistically.

If pseudospin symmetry is conserved, then, if the mag-netic moment of the states in the doublet is known, themagnetic dipole transition between the pseudospin doubletscan be determined [8]. For example, using the magneticmoment of the ground state of 39Ca, the predicted magneticdipole transition agrees with the measured transition withinexperimental error. A global analysis of such transitions formany nuclei shows that these predictions are approximatelyvalid [9]. Similar relations hold for Gamow Teller transi-tions in beta decay as well.

Nucleon-Nucleus Scattering The elastic scattering of medium energy nucleons from

nuclei can described successfully with a relativistic opticalmodel with complex scalar and vector potentials. Thescalar and vector potentials determined by fitting the scat-tering data are approximately equal in magnitude but differ-ent in sign even though they are complex [10].

The scattering amplitude consists of two parts, oneindependent of pseudospin symmetry and one pseudospindependent. The pseudospin dependent amplitude has beenextracted from the measured spin polarization and the spinrotation [11,12]. For the scattering angles measured thepseudospin dependent amplitude is only 10% of thepseudospin independent amplitude. For lower energynucleons, however, the pseudospin breaking increases [13].

Antinucleon-Nucleus Scattering A nucleon changes into an antinucleon under charge

conjugation. Under charge conjugation the scalar potentialremains unchanged but the vector potential changes sign.Thus, an antinucleon in a nuclear environment will experi-ence vector and scalar potentials that are approximatelyequal. This implies spin symmetry. Indeed, spin polarizationmeasured in antinucleon nucleus scattering is consistentwith zero, implying spin symmetry [14].

Fundamental Theory of the Strong Interactions and Pseudospin Symmetry

Quantum Chromodynamics (QCD), the fundamentaltheory of the strong interactions, predicts that the vector

and scalar potentials in nuclei are almost equal in magnitudeand opposite in sign [15], which is consistent with approxi-mate pseudospin symmetry. The difference in sign comesfrom the fact that the quark condensate of the vacuum isnegative.

Future Study This connection with QCD suggests that there may exist

a more basic rationale for pseudospin symmetry in nucleibased on the interaction between quarks that needs to beexplored. For example, one question is “Why is pseudospinsymmetry valid for nuclei, whereas spin symmetry is validfor hadrons?”

1. A. Arima, M. Harvey and K. Shimizu, Phys. Lett. B, 30 (1969)517; K. T. Hecht and A. Adler, Nucl. Phys. A, 137 (1969) 129.

2. J. N. Ginocchio, Phys. Rev. Lett., 78 (1997) 436. 3. P. R. Page, T. Goldman, and J. N. Ginocchio, Phys. Rev. Lett.,

86 (2001) 204. 4. B. D. Serot and J. D. Walecka, in Advances in Nuclear

Physics, edited by J. W. Negele and E. Vogt, Vol. 16 (Plenum,New York, 1986); P.-G. Reinhard, Rep. Prog. Phys., 52(1989) 439.

5. J. N. Ginocchio and D. G. Madland, Phys. Rev. C, 57 (1998) 1167. 6. J. N. Ginocchio, Phys. Rev. C, 66, (2002) 064312. 7. J. N. Ginocchio, A. Leviatan, J. Meng, and S.-G. Zhou, Phys.

Rev. C, 69 (2004) 034303. 8. J. N. Ginocchio, Phys. Rev. C, 59 (1999) 2487. 9. P. von Neumann-Cosel and J. N. Ginocchio, Phys. Rev. C, 62

(2000) 014308. 10. R. W. Fergerson et al., Phys. Rev C, 33 (1986) 239. 11. J. N. Ginocchio, Physical Rev. Lett., 82 (1999) 4599. 12. H. Leeb and S. Wilmsen, Phys. Rev. C, 62, (2000) 024602. 13. H. Leeb and S. A. Sofianos, Phys. Rev. C, 69, (2004) 054608. 14. J. N. Ginocchio, Lecture Notes in Physics, 641 (2004) 219. 15. T. D. Cohen, R. J. Furnstahl, D. K. Griegel, and X. Jin, Prog.

in Part. and Nucl. Phys., 35 (1995) 221.

JOSEPH N. GINOCCHIO


Exploding Stars, Neutrinos, and Nucleosynthesis

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Exploding Stars, Neutrinos, and Nucleosynthesis

GAIL MCLAUGHLIN

Exploding Stars Supernovae are some of the most violent, energetic

events that occur in the universe. The most recent super-nova in our Galaxy that could be seen from earth wasCassiopeia A, which occurred about 1680. This supernovawas the explosion that ended the life of a massive star, alsocalled a core collapse supernovae. Observationally, super-novae are divided into two main types, Type I and II, wherethe classification is based on their spectral features. Type Isupernovae do not have hydrogen lines in their spectrawhereas Type II supernovae do. Type II supernovae arealways core collapse supernovae, but only some of Type Isupernovae are.

Type Ia and core collapse supernovae are very differentobjects. A Type Ia supernovae occurs when a white dwarfstar, such as a carbon–oxygen white dwarf, is in a binarysystem with an ordinary star. The white dwarf star slowlyaccretes material from the outer envelope of its companion.Once sufficient material has been accreted so that the den-sity or temperature on the white dwarf becomes quite high,for example, densities of 2*109 g/cc, a runaway nuclearfusion reaction results. The energy released from the fusionprocess powers an explosion. Type Ia supernovae are con-sidered to have nearly constant luminosity and are thereforeused as “standard candles,” meaning that their apparentluminosity is a way to judge their distance. Comparing theinferred distance with the redshift is one of the ways thathas been used to measure (and discover!) the accelerationof the universe.

A Type II supernova comes from the explosion thatends the life of a star that has a mass of around ten to thirtytimes the mass of our sun. Throughout most of their lives,stars shine by burning hydrogen to helium, as is happeningright now in the sun. The energy released from the bindingof free nucleons into helium provides the pressure that sup-ports the star against gravity. After the sun has exhaustedthe majority of its hydrogen supply, it will burn helium intocarbon and oxygen. The gravitational pressure will not besufficient to compress the star to temperatures requiredto burn past oxygen and so the sun will end its life as acarbon–oxygen white dwarf.

A more massive star will continue to burn beyond car-bon and oxygen and create heavier nuclei all the way to

iron, which is the most tightly bound element. An “onionring” structure develops in the star with hydrogen as theouter ring, then helium and the heavier elements, and ironat the core. The iron core is initially supported by degen-erate electron pressure, as is the case for a white dwarf. Asthe core reaches higher densities electron capture sets inand the core becomes unstable. The inner core quicklycollapses to nuclear density. At this point matter becomesvery incompressible and the core rebounds. When infall-ing material hits outgoing material a shock wave isformed, which begins to propagate outward. Up to thispoint, the explosion has been successfully modeled onlarge computers. However, the details of how the shockejects the outer layers of the star have never been convinc-ingly demonstrated.

This should not come as a surprise. The problem of the-oretically modeling the explosion is difficult because itcombines many areas of physics, such as general relativity,hydrodynamics, neutrino, and nuclear physics. Also, theenergy balance is very delicate. Neutrinos carry away about99% of the binding energy of the iron core, about 1053 erg.Only a small fraction of the total energy goes into thekinetic energy of the shock. Finally, constructing detailedmodels is computationally very intensive, and the effortrequired for three-dimensional models with sufficient gran-ularity is still prohibitively large. All of this does not imply,however, that we cannot study other aspects of the super-nova. In the following we shall see that there are many phe-nomena related to supernovae about which we can learneven without yet having a definitive theoretical model ofthe explosion mechanism.

Before we come to this, we would like to complete ourbrief tour of exploding stars. Type Ib and Ic supernovae arealso without hydrogen lines, but these are not thermonu-clear detonations off the surfaces of white dwarfs as onemight expect from the name. Instead, Type Ib and Ic arecore-collapse supernovae, similar to the Type II supernovaedescribed earlier, but distinguished by the fact that the pro-genitor lost its hydrogen envelope (Ib) or hydrogen andhelium envelope (Ic) prior to collapse.

Gamma ray bursts, first discovered more than thirtyyears ago, are intense bursts of gamma rays. The astrophys-ical origin of these bursts was largely mysterious up until

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very recently. Over the last few years the situation is evolv-ing very rapidly, as significant amounts of data from satel-lites and ground based telescopes are being gathered.Gamma ray bursts can be classified into long and shortduration bursts. In the 1990s data was taken on the longduration bursts, and it was discovered that they have coun-terparts in the X-ray, optical and radio parts of the spectra,the “afterglow,” which goes on for days or even months (inthe case of radio emission) after the initial gamma rayburst. More recently, a few cases were discovered thatshow a “bump” in the light curve of the afterglow. Thisbump can be fit to a traditional core-collapse supernovaelight curve, that is, the kind that is driven by the beta decaysof nickel and cobalt. In a few cases spectra have been takenand the spectra look remarkably like those seen in Type Ibor Ic data. The clear suggestion is that gamma ray burstscome from some sort of unusual core collapse supernovaevent.

Nuclear physics plays many roles in all of these events. Itis nuclear reactions that produce the energy that powers theexplosion in Type Ia supernovae. It is the nuclear equation ofstate that determines the point at which the collapse is haltedand the shock wave is formed in core collapse supernovae. Itis the neutrino scattering reactions that may provide the nec-essary energy to keep the shock wave moving, once it has

been produced. Furthermore, all of these types of superno-vae produce unique nucleosynthesis products that makeimportant contributions to the amount and type of elementsthat exist in the solar system today.

Neutrinos are an essential component for understandingcore collapse supernovae for many reasons, the most obvi-ous being that they carry the vast majority of the energy.The core formed by the collapse of the star, called a proto-neutron star, is so hot ( 100MeV) and dense ( 1014g/cm3),that not only are the photons trapped but the neutrinos areas well. Neutrinos are produced thermally and are emitted,about 1057 of them, in all three flavors, electron, mu, andtau, as well as their anti-particles. Because neutrinos inter-act only by the weak interactions, they decouple at the sur-face of the core where the temperature is around 10 MeV–25 MeV and exit the star in the first tens of seconds.

In contrast, photons do not escape for many hours. Notonly do the neutrinos emerge first but in most cases theymay be all that we can detect here on earth. For a supernovain our galaxy the photons may never be seen at all, becausemost of our Galaxy is obscured by dust. This is the reasonwhy, although estimates of the Galactic core collapse super-nova rate are around every 50 years or so, the last supernovaobserved on earth occurred more than 300 years ago.

Neutrinos from a core collapse supernovae weredetected only once, from Supernova 1987a in the LargeMagellanic Cloud, by the Kamiokande and IMB detectors.In the mean time, much larger neutrino detectors are on-line

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Figure 1. Schematic sketch of a supernova. The neutrinosleak out of the proto-neutron star on a time scale of around10 seconds, while the shock moves out very quickly, in afraction of a second. Neutrinos of different energy andflavor decouple at slightly different densities in the proto-neutron star.

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Figure 2. Observational data from a halo star that showsabundances of r-process elements. The line shows the solarsystem distribution. Figure from Cowan and Sneden astro-ph/0409552.

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that could potentially record thousands of events from agalactic supernova. Although supernovae are rare, such adetection is much anticipated. As discussed earlier, neutri-nos provide a window into the center of the supernova. Neu-trinos will scatter last at the surface of the core, and as aresult their spectrum reflects the conditions at this point.

Nucleosynthesis As well as being a unique source of neutrinos, super-

novae are also the site of unique types of element syn-thesis. Explosive burning in core-collapse supernovaeoccurs as nucleons and nuclei are fused together as theshock wave from the explosion passes through. Thisresults in a considerable production of Nickel-56, whichbeta decays first to Cobalt-56 and then to Iron-56. Afterthe beta decay the daughter nucleus decays by emitting agamma ray. The decay photon is thermalized as it scat-ters off surrounding material and drives the supernovalight curve. In fact, it is the beta decay lifetimes of thesenuclei that determine the timescale of the observed lightcurve. The iron produced in explosive burning also con-tributes significantly to the galactic inventory of thiselement.

In addition to explosive burning, there are other types ofnucleosynthesis that may occur in core-collapse supernovae,such as rapid neutron capture (or r-process) synthesis.“Rapid” means that the time scale for neutron captureis short compared to the time scale for beta decay. Ther-process is responsible for almost half the heavy elements(those with mass number A > 100), including the transuranicelements such as Uranium and Thorium. Although themechanism for producing these elements has been knownsince the late 1950s, the astrophysical site remains a mys-tery. Recent observational results of low metallicity halostars show that the abundance pattern for r-process elementsin very old stars is very similar to that observed in our ownsolar system. This suggests that the same type of event isproducing the same elemental pattern over and over again.

The neutrino-driven wind of the core supernova is aseductively simple possibility for producing these ele-ments. Supernovae occur on the right time scale in order toaccount for the amount of r-process material present in thegalaxy. Also, core collapse supernovae begin occurring rel-atively early on, explaining the presence of r-process ele-ments in old stars. The neutrino-driven wind occurs afterthe first tenths of seconds when the shock has moved farout in the star. The neutrinos continue to impart a smallamount of their energy to the material on the surface of theproto-neutron star and push these free neutrons and protonsout in a wind. The prospects for making the r-processdepend on the relative number of free neutrons and protons,which in turn depends on the relative rate of electron neu-trino and anti-neutrino capture on free nucleons in thiswind. The electron anti-neutrinos, having decoupledslightly deeper in the core than the electron neutrinos, haveslightly higher energy than the neutrinos. The balance ofthe charged current neutrino interactions therefore drivesthe material neutron rich and creates a potentially viableenvironment for the r-process.

Detailed calculations have shown that the neutrino-drivenwind comes very close to producing the r-process elements.One of the reasons that this environment is not completelysuccessful is again related to the neutrinos. An importantearly stage of the r-process involves alpha particles and neu-trons. A successful r-process requires many neutrons peralpha particle. However, if the neutrino flux is large chargedcurrent reactions convert neutrons to protons that immedi-ately combine with neutrons to form more alpha particles,and the number of neutrons per seed nucleus becomes toosmall. We must find either find physics missing from our cal-culation of the wind, or look to another environment.

Figure 3. This figure shows the rate of neutrino-anti-neutrino annihilation above a GRB accretion disk in unitsof eV/cm3/s. The black hole is in the center and the solidlines show the density scale height of the disk. Figurecreated by Jim Kneller.


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Exotic Supernovae There have been hints that there is not just one way in

which a core collapse supernovae explodes but instead arange of possibilities. As mentioned earlier, some of thesebursts have spectra that look similar to Type Ib and Icsupernovae. What makes an “ordinary” core collapsesupernovae and what makes a gamma ray burst? Theoristshave speculated that it is the degree of rotation of the pre-supernova star. Stars with too much rotation do not collapseand bounce efficiently enough to produce a robust shock.Instead the core collapses into a black hole, surrounded byan accretion disk. Neutrinos are emitted copiously off ofthe surface of this disk. Depending on the accretion rate andthe spin parameter of the black hole, the neutrinos may ormay not be trapped in the inner portion of the disk. In eithercase, only electron type neutrinos and antineutrinos are pro-duced because the temperatures are lower than they are inthe core of the proto-neutron star in the regular supernova.The geometry of the disk provides maximum opportunityfor neutrino-anti-neutrino annihilation. Heating fromneutrino-anti-neutrino annihilation, combined with electro-magnetic extraction of energy from the rotating black holemay be responsible for powering the burst. The burst itselfconsists of ultra-relativistic ejecta emitted directly abovethe black hole. Models for this process are currently beingdeveloped and it will likely prove even more challengingthan modeling the traditional core collapse supernova envi-ronment due to the more complicated geometry and thestronger effects of general relativity.

The neutrinos that are emitted from the disk have aver-age energies on the order of a few MeV. In addition tothese, very high-energy neutrinos of around 1015 eV can beproduced by photo-pion reactions. High energy protons canscatter off the radiation field of the source and producepions that decay into muons and neutrinos. Because gammaray bursts are rare, we are unlikely to observe one in ourGalaxy, but very high-energy neutrinos can be detectedeven if they originate from objects well beyond our Galaxy.It may be possible to observe these neutrinos with kilometercubed detectors such as Ice Cube and Amanda.

This new type of core collapse supernova will produce aunique set of nucleosynthesis products. Although theseevents are fairly rare, perhaps 10−5 per year per galaxy asopposed to 10−2 per year per galaxy for typical supernovae,they can still contribute significantly to cosmic elementabundances. What elements are produced in gamma raybursts? It is difficult to know for certain until more com-plete hydrodynamic models exist. However, some things

we can guess. In order to account for the “bumps” in the thelight curve that look like standard supernovae, one needsnickel, on the order of half a solar mass. So some nickelmust be synthesized in the burst. Does it occur from explo-sive burning as in the standard core collapse supernovae, ordoes it come from material ejected from an accretion disk,perhaps in a wind? The material in the disk is hot enough sothat it is dissociated into free neutrons and protons. Not allthe material will be accreted into the black hole, some willbe ejected and the free neutrons and protons will recombineinto nuclei. If the material is sufficiently neutron rich, aswould be the case for very high accretion rates, we mayfind the r-process. If the material is roughly 50% neutronsand 50% protons, considerable nickel will be produced, butperhaps also an unusual smattering of other rare nuclei.

Outlook In summary, the subject of supernovae is a unique combi-

nation of many different branches of physics, and there aremany different ways in which we can probe their inner work-ings. Traditional astronomy uses photons of all wavelengthsand spectra can be used to probe nucleosynthesis products.We can now supplement this information by measuring neu-trinos from future galactic supernovae. Theoretically there ismuch to learn by combining nuclear reactions, neutrino scat-tering, general relativity, and much more. In addition to thatwe are discovering whole new types of events that are alsoassociated with supernovae. Whatever the future of super-nova research brings, it promises to be an exciting time.

References 1. H. A. Bethe, Supernova mechanisms, Rev. Mod. Phys., 62,

801–866 (1990). 2. A. Burrows and T. Young, Neutrinos and supernova theory,

Phys. Rep., 333, 63–75 (2000). 3. A. I. MacFadyen and S. E. Woosley, Collapsars: Gamma ray

bursts and explosions in failed supernovae, Astrophys. J., 524,262–269 (1999).

4. P. Meszaros, Theories of gamma-ray bursts, Ann. Rev. Astr.Astroph., 40, 137–169 (2002).

5. E. M. Burbidge, G. R. Burbidge, W. A. Fowler, F. Hoyle, Syn-thesis of the elements in stars, Rev. Mod. Phys., 29, 547(1957).

6. B. S. Meyer, The r-, s-, and p-processes in nucleosynthesis,Ann. Rev. Astr. Astroph., 32, 153–190 (1994).

7. C. Sneden, J. J. Cowan, Genesis of the heaviest elements inthe Milky Way Galaxy, Science, 299, 70 (2003).

8. K. Langanke, G. Martinez-Pinedo, Nuclear weak-interactionprocesses in stars, Rev. Mod. Phys., 75, 819 (2003).

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High-Resolution Gamma-Ray Spectroscopy at TRIUMF-ISAC

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High-Resolution Gamma-Ray Spectroscopy at TRIUMF-ISAC

Introduction It is no accident that the rapid techni-

cal evolution of radioactive beam facili-ties has coincided with challenges to thestandard models of nuclear structure andfundamental interactions. In nuclearstructure, the shell model is a de factostandard model. The properties and sys-tematics of nuclei near stability are wellunderstood in terms of the magicnucleon numbers at shell closures. How-ever, when confronted with experimen-tal data on increasingly exotic nuclei,the model fails. The near-stability magicnucleon numbers disappear, and newones emerge [1]. This is evidenced forexample by the energies and γ transitionrates of excited states. These excitationsmay be probed by reactions inducedwith accelerated radioactive beams, orby a parent β decay. At the same time,high production yields for selected iso-topes allows for very high precisionmeasurements of specific decay pro-cesses. Because β decay is a nuclearmanifestation of the weak interaction,high precision measurements of nuclearβ decay provide a strict test of funda-mental symmetries [2].

Gamma-ray spectroscopy has longbeen a cornerstone of decay and in-beam nuclear physics experiments.For these measurements, high-puritygermanium (HPGe) detectors deliverthe necessary energy resolution andefficiency. Signal-to-noise, that is,peak-to-total ratios, can be furtherimproved by surrounding the HPGewith inorganic-scintillator escape sup-pression shields that veto events withonly partial photon energy deposition.Gamma-ray spectroscopy is mostpowerful in multi-γ or γ-particle coin-

cidences to isolate specific decaybranches from otherwise overwhelm-ing backgrounds.

The Tri-University Meson Facil-ity (TRIUMF) cyclotron can deliverup to 100 µA 500 MeV proton beam tothe Isotope Separator and Accelerator(ISAC), a modular high-power ISOL-type radionuclide production and massseparation system. Activities are ion-ized, extracted, and delivered to thelow-energy area for decay experi-ments, or injected into radio-fre-quency quadrupole and drift-tubelinear accelerators (DTLs) for deliveryto higher-energy experimental sta-tions. ISAC-I accelerates ions withmass-to-charge A/q<30 up to 1.8MeV/u primarily for nuclear astrophysicsexperiments. When completed in2007, the charge state booster andsuperconducting DTLs of ISAC-IIwill deliver beams with masses up toA ~ 150 at energies up to 6.5 MeV/u

for near- or above-barrier nuclearphysics experiments [3].

The 8� spectrometer The HPGe detector array now

known as the 8π spectrometer beganas a joint venture between Universitéde Montréal, McMaster Universityand Atomic Energy of Canada Lim-ited (AECL). It was named after aninitial conceptual design with a 4πinner calorimeter and a 4π suppressionscheme. The 8π was installed in 1985at AECL Chalk River’s TandemAccelerator Superconducting Cyclo-tron (TASCC) facility, where it wasused primarily for pioneering work inhigh-spin nuclear structure. In 1997,the 8π moved to Lawrence BerkeleyNational Laboratory, and in 2000 itwas repatriated to the ISAC low-energy beam area [4].

The 8π (Figure 1) has been recon-figured for high-precision β-decay

Figure 1. The 8π, downstream half of SCEPTAR, and tape system.

GNPN_A_53968.fm Page 1 Thursday, August 11, 2005 12:51 PM



measurements. The inner calorimeterand front suppressor shields havebeen removed, and the 20 HPGe andbismuth germanate (BGO) suppres-sors have been moved forward.Hevimet collimators prevent theBGO suppressors from viewing γrays from the HPGe focus. Delrinabsorbers stop β particles from enter-ing the HPGe while minimizingbremsstrahlung.

Associated Systems SCEPTAR, the Scintillating Elec-

tron-Positron Tagging Array, consistsof twenty thin plastic scintillators (∆Eof 500 keV for minimum ionizingelectrons) in vacuum subtending 80%of the solid angle around the 8π focus(Figure 2). Each HPGe is co-linear tothe focus of the array with a uniqueSCEPTAR scintillator.

The tape system (Figure 1) is acontinuous loop up to 150 m longmoving at up to 1.3 m/s. It is intendedto remove long-lived activities (daugh-ters or beam contaminants) out of thefocus of the detectors and behind alead wall. With SCEPTAR, the tapesystem, and Delrin absorbers installed,the 8π has a γ-ray photopeak efficiency

of 1.0% at 1.332 MeV, and a peak-to-total ratio of 41% for 60Co.

The upstream 10 detectors ofSCEPTAR may be replaced with thePentagonal Array Conversion Elec-tron Spectrometer (PACES), up tofive cryogenically cooled 5 mm thickSi(Li) detectors subtending 6% solidangle (Figure 2) [5]. PACES hasrecently been used in an in-beam experi-ment elucidating low-spin 156Dy struc-tures populated by 156Ho β decay [6].

Science Highlights The High Precision Program: The

8π and its new associated equipmentare intended for high precision(~0.05%) measurements of lifetimesand branching ratios in superallowed0+→0+ Fermi β decays [2,4]. Thesemeasurements test the ConservedVector Current hypothesis and theunitarity of the CKM quark-mixingmatrix. High precision γ and conver-sion electron measurements areneeded not only for branching ratios,but in selected cases, also for measur-ing lifetimes. For example, 34Ar andits daughter 34Cl both β decay andhave nearly the same half-lives, so it isimpossible to disentangle their β

decay curves and measure the 34Arhalf-life with the necessary precision.However, 34Ar also emits γ rays fol-lowing the β decay, so γ-ray countingis promising for measuring the 34Arhalf-life with the needed precision.The technique has been investigated indetail with 26Na decay, to compare tra-ditional β counting with γ counting.The first measurement in this programhas been the half-life of 18Ne, yieldinga measurement with a statisticaluncertainty of ~0.1% [7]. Measure-ments on other superallowed Fermiβ-decay nuclei will continue as ISACbeams become available.

176Lu: The first measurement withthe 8π at ISAC was the half-life ofthe geochronometer 176Lu. By count-ing γ-γ coincidences with 8π HPGedetectors, several sources of system-atic uncertainty were eliminated. Ahalf-life of 176Lu of 40.3(3) billionyears was reported. [8]

High-K isomers are a prime exam-ple of the interplay between collectiveand single-particle degrees of freedomin nuclear systems [9]. The 8π wasfirst to observe the M4 and E5 γ raysde-exciting a high-K isomer, namelythe 31-year 178m2Hf isomer. These are~10−4 branches, and establish a reducedhindrance factor of ~100 for allobserved K-isomer decay branches ofthis isomer [10]. The 8π also has beenused in a campaign to identify newhigh-K isomers in ISAC beams [11].In the first experiment, a new isomerin 174Tm with a half-life of 2.3 s hasbeen identified [12]. The tape systemwas critical for removing long-liveddaughters and beam isobars from thefocus of the HPGe detectors.

11Li: The halo nucleus 11Li and itsdaughter 11Be are classic examples ofnovel nuclear behavior at the extremesof weakly bound nuclei. However,despite numerous experimental studies,

Figure 2. Downstream half of SCEPTAR (left); PACES (right) with three of fiveSi (Li) installed.




discrepancies persist in γ ray intensitiesfollowing β decay and in the levelscheme for neutron-unbound 11Bestates ([13–15] and references therein).

In one of the first 8π in-beam experi-ments, 500 atoms/s of 11Li were depos-ited on an aluminum foil at the arrayfocus. The lineshapes for 10Be γ rays(Figure 3) are Doppler broadened due tothe recoil of the residue following 11Be*neutron emission. These lineshapesdepend on the energies, spins, branchingratios, and lifetimes of states in the β-n-γdecay chain. The data were analyzed bycomparison with Monte-Carlo simula-tions of the decay of 11Li and of the stop-ping of the 10Be recoil in aluminum.Lifetimes of states in 10Be were mea-sured, and limits on n-γ correlationparameters were consistent with spins

allowed in the observed β-n-γ cascades.The data also confirmed the existence ofan 8.03MeV state in 11Be first postu-lated in Ref. [13]. The data show clearevidence that the 8.81MeV state decaysby neutron emission to the 10Be 2− and2+

2 states, but no evidence for decay tothe 1− state. This is consistent with aspin and parity of 5/2− for the 8.81MeVstate in 11Be, raising questions about thestructure of this state and the possiblehalo-neutron survival through a coredecay process [14]. However, like allprevious measurements in 11Li, discrep-ancies remain; Fynbo etal [15] did notreport any evidence for the 8.03MeVstate in 11Be. The experiment hasrecently been repeated with the 8π andSCEPTAR, generating a data set ~20times larger. Along with resolving

outstanding intensity and feeding dis-crepancies, with higher statistics, n-γangular correlation parameters can beconstrained for spin assignments. Also,by vetoing co-linear β-γ coincidences,bremsstrahlung continuum is suppressed;for example, the overall continuumbackground near the 219keV 10Be lineis reduced by 40% [16].

TIGRESS Accelerated radioactive beams can

be used to access excited states inexotic nuclei through mechanismssuch as inelastic scattering, particletransfer, and fusion-evaporation. Eachhas its own role for probing collectiveor single-particle modes over ranges ofexcitation energy and angular momen-tum. However, experiments withradioactive beams face additional chal-lenges of limited beam intensity, iso-baric contamination, and Doppler shiftof γ rays from reaction products. HPGeouter-contact segmentation and digitalsignal processing provide high effec-tive granularity for measuring the lab-oratory-frame γ emission angle. Thearrays become compact and offer acost-effective solution for high effi-ciency without excessive Doppler cor-rection uncertainty. Large arrays ofhigh effective-granularity HPGe detec-tors have been installed at many of thepremier radioactive beam facilities,including CLARION at Oak Ridge,SeGA at Michigan State, Miniball atREX-ISOLDE, and EXOGAM atGANIL [4]. The 8π’s small and unseg-mented HPGe detectors are best suitedto their current role in decay spectros-copy. In-beam spectroscopy, with thehigh-energy, high-mass beams fromISAC-II, requires a new array.

The TRIUMF-ISAC Gamma-RayEscape Suppressed Spectrometer(TIGRESS) will comprise 12 units ofHPGe four-crystal “clover” detectors,

Figure 3. Selected Doppler-broadened γ rays and fits in 11Li β− decay, takenfrom [14].




(Figure 4), with back and side suppres-sors mounted to the cryostat. These unitsare arranged in a rhombicuboctahedralgeometry and can be inserted to a close-packed configuration for a high photo-peak efficiency of ~12% for 1MeV pho-tons, or can be withdrawn for insertionof front-suppressor BGO plates in ahigh-peak-to-total configuration. In bothcases a spherical volume with a radiusof 11cm is available for auxiliary detec-tors and target chambers. Each of the>38% relative efficiency HPGe crystalouter contacts is segmented eightfold,into four quadrants and with a lateraldepth segmentation, for sub-segmenteffective granularity through waveformanalysis. All signals will be digitizedwith custom-built readout and triggeringsystems developed in parallel with thosefor another major TRIUMF initiative,KOPIO [17]. The support frame willallow rapid redeployment from the high-efficiency to high-peak-to-total configu-

rations in one working day with no re-cabling or detector removal. First Cou-lomb excitation experiments with fourunits are expected in mid-2006, withcompletion of the array in 2009 forfusion-evaporation and particle-transferreactions in concert with auxiliarycharged particle and recoil detectors.

A prototype HPGe detector unitwas shown to meet expectations. Instandard tests with 1332 keV gammarays from 60Co sources, all four AC-coupled center contact full-volumesignals gave better than 2.3 keV energyresolution, and the efficiency of thefull unit was 215% in addback mode.All outer contacts, instrumented withroom temperature FETs, delivered<3.2 keV resolution [18]. The single-interaction position sensitivity, asdefined by Vetter et al. [19], is0.44 mm [20]. A set of prototype sup-pressor shields yielded peak-to-totalratios of 35% and 50% in the high-

efficiency configuration and highpeak-to-total configurations. [21].

Summary High energy-resolution γ-ray spec-

trometry is a powerful and versatiletechnique in nuclear physics research.At ISAC-I, the 8π and associated tapesystem, SCEPTAR and PACES havebeen installed for high-precision β-decay measurements, and have alreadydemonstrated their broad applicabilityto outstanding nuclear physics ques-tions. The TIGRESS array will pro-vide the high efficiency and higheffective granularity needed to meetthe challenges of nuclear structureexperiments with accelerated radioac-tive beams from ISAC-II.

Acknowledgments Major equipment and operating

support for the 8π, SCEPTAR, andTIGRESS is provided by the NationalScience and Engineering ResearchCouncil of Canada. The U.S. Depart-ment of Energy has contributed toPACES, the tape system, andupgraded 8π electronics. TIGRESSprototype detectors were fundedthrough the Canadian Foundation forInnovation and Ontario InnovationTrust. TRIUMF receives federal fund-ing through a contribution agreementwith the National Research Council ofCanada.

References 1. H. Grawe, Act. Phys. Pol., B34, 2267

(2003). 2. I. S. Towner and J. C. Hardy, J. Phys.

G, 29, 1997 (2003). 3. R. E. Laxdal, Nucl. Instr. Meth. Phys.

Res. B, 204, 400 (2003). 4. C. E. Svensson et al., Nucl. Inst. Meth.

Phys. Res. B, 204, 666 (2003). 5. E. F. Zganjar, private communication. 6. W. D. Kulp. private communication. 7. M. B. Smith, private communication.

Figure 4. The TIGRESS Concept. 12 unit array, high-efficiency (Hi-ε)configuration; clover HPGe configuration, showing quadrant and lateralsegments; suppressors in Hi-ε and high peak-to-total (Hi-P/T) configurations,identifying back catchers (J), side catchers (K), and front shields (L).




8. G. F. Grinyer et al., Phys. Rev. C, 67,014302 (2003).

9. P. M. Walker and G. D. Dracoulis,Nature (London), 399, 35 (1999).

10. M. B. Smith et al., Phys. Rev. C, 68,031302(R) (2003).

11. M. B. Smith et al., Nucl. Phys. A, 746,617c (2004).

12. R. S. Chakrawarthy et al., ENAM’04Proceedings, in press (2004).

13. N. Aoi et al., Nucl. Phys., A616, 181c(1997).

14. F. Sarazin et al., Phys. Rev. C, 70,031302(R) (2004).

15. H.O.U. Fynbo et al., Nucl. Phys.,A736, 39 (2004).

16. C. Mattoon, private communication. 17. D. Bryman and L. Littenberg, Nucl.

Phys. B, 99, 61 (2001). 18. H. C. Scraggs et al., submitted to Nucl.

Inst. Meth. Phys. Res. A, and TRIUMFPreprint PP-04–23

19. K. Vetter etal., Nucl. Inst. Meth. Phys.Res. A, 452, 223 (2000).

20. C. E. Svensson et al., accepted, Nucl.Inst. Meth. Phys. Res. A.

21. M. Schumaker et al., private com-munication.

GREG HACKMAN

TRIUMF, Vancouver, BC, Canada

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Radioactive Ion Beam Facility in Brazil (RIBRAS)

R. LICHTENTHÄLER, A. LÉPINE-SZILY, V. GUIMARÃES, M.S. HUSSEIN Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo SP

Nuclear physics has been goingthrough a major evolution over the lastdecade with the possibility of produc-ing secondary beams of nuclei farfrom the stability line (exotic nuclei).Many new facilities have been put towork in order to investigate nuclei atextreme conditions of density, temper-ature, and with a high number of pro-tons or neutrons. In particular, thepossibility of using exotic nuclearbeams has opened an exciting field ofinvestigation in nuclear physics withstrong implications in nuclear astro-physics.

The Pelletron Laboratory of theUniversity of São Paulo installed thefirst South American Radioactive Ionbeams device (RIBRAS) [1–3]. Thisfacility extends the capabilities of theoriginal Pelletron accelerator by pro-ducing secondary beams of unstablenuclei.

A picture of this facility is shownin Figure 1.

The most important components inthis facility are the two new super-conducting solenoids. The solenoidshave 6.5T maximum central field(5T.m axial field integral) and a 30 cmclear warm bore, which correspondsto an angular acceptance in the rangeof 15deg ≥ θ ≥ 2deg.

The solenoids were manufacturedby Cryomagnetics INC (USA) andwere designed to operate in connec-tion with the Linac post-accelerator ofmaximum energy of 10 AMeV, pres-ently under construction. With theLINAC, the energy of the primarybeam will be about 2–3 times largerthan the maximum energy of the

present Pelletron Tandem of 8 MVterminal voltage (3–5 AMeV).

The presence of the two magnetsis very important to produce pure sec-ondary beams. The first solenoidmakes an in-flight selection of thereaction products emerging from theprimary target at forward angles. Asthe first magnet transmits all ionswith the same magnetic rigidity(Bρ)2 = mE/q2 the purity of the radio-active secondary beam in the mid-scattering chamber can be rather poor.With two solenoids, it is possible touse differential energy loss in adegrader foil, located at the crossoverpoint between the magnets. Thisdegrader foil will allow the secondsolenoid to select the ions of interestby moving the contaminant ions outof its bandpass. Time of flight tech-

nique using a pulsed primary beam isalso very useful to identify nuclei ofinterest in the secondary beam. Thebuncher system to pulse the primarybeam of the Pelletron accelerator ispresently being installed.

An additional future possibilityfor the two solenoid system is theproduction of tertiary beams using asecondary target in the mid scatteringchamber. The second solenoid can betuned to select a different magneticrigidity producing low intensity (1–100/s) tertiary beams like 9Li, 8He[4,5]. This is, in principle, possiblewith secondary beams of 107 p/s andassuming a typical conversion effi-ciency of 10 −5 for the secondaryreaction.

The two solenoids are presentlyinstalled in the 45B Pelletron beam

Figure 1. RIBRAS Facility installed in the 45B Pelletron beam line (fotoEduardo Cesar).




line. It should be noted that setting upof the double solenoid system prior tothe completion of the LINAC post-accelerator is an important issue. Thismakes possible to begin experimentswith a facility that is similar to theTWINSOL system at Notre DameUniversity [5]. This first stage withthe Pelletron primary beam of 7,6Li of3–5 AMeV and 1 µAe maximum cur-rent, allows the production of second-ary beams such as 7Be, 8B, 8Li, 6Hewith intensities around 104 to 106 par-ticles per second. With these intensi-ties one can perform measurements ofelastic scattering angular distributionsand studies of the interaction potentialof systems involving exotic projec-tiles allowing the investigation ofphenomena such as proton and neu-tron halo in nuclei.

Probably the most importantimpact of the research with lowenergy RIB is in nuclear astrophys-ics. The possibility of measuring thecross sections of capture reactions ofastrophysical interest involvingexotic nuclei will certainly haveimportant consequences in the mod-els of the primordial as well as in theexplosive nucleosynthesis. The pri-mordial nucleosynthesis involvesreactions with light nuclei thatwould be accessible with RIBRASbeams. In the inhomogeneous modelof the primordial nucleosynthesisthere are new paths near the neutrondrip line involving nuclei like 8Li,6He that would lead to the synthesisof 11B [6].

The RIBRAS facility will haveseveral important up-grades providedby the linear post-accelerator(LINAC). In particular, radioactiveion beams with higher energy (up to10 MeV/nucleon) and higher mass(perhaps up to A = 50) can be pro-duced with beam purities approaching

80% in many cases. In addition, thepulsed time structure of the beam willprovide a time-of-flight parameterthat can be used to reduce back-grounds in many experiments. On amore speculative note, if uraniumbeams could be accelerated to ener-gies of a few MeV per nucleon, trans-fer induced fission reactions could beused to produce a wide variety of veryneutron rich fission fragments. Thebeams formed in this way are notlikely to be very pure, but they couldbe useful in a number of experiments.However, this extended project wouldrequire the installation of a low-β ini-tial acceleration stage and an ECRsource at the LINAC.

The first radioactive beams fromthe RIBRAS facility were deliveredin February 2004 during the XIII J. A.Swieca Summer School on Experi-mental Nuclear Physics. The 8Li and6He particles produced by the reactionof the 7Li primary beam on the 9Beprimary target were focused by thefirst solenoid in the scattering cham-ber located at the crossover pointbetween the two solenoids. Only thefirst solenoid was used in this firsttest.

The production system (primarytarget) consists of a gas cell, mountedin a ISO chamber followed by a tung-

sten Faraday cup that suppresses theprimary beam and measures its cur-rent. The gas cell was mounted with a2.2 µm Havar entrance window and a12 µm thick 9Be vacuum-tight exitwindow, which plays the role of theprimary target and the window of thegas cell at the same time. The gasinside the cell has the double purposeof cooling the Berilium foil heated bythe primary beam and as productiontarget. In case we want to use a gastarget to produce secondary beams,the Berilium foil can be replaced byanother Havar foil and the pressureinside the cell can be increased up toseveral Bars.

In Table I we present some typi-cal production rates and reactionsused at Notre Dame and at RIBRAS,São Paulo.

The secondary beam profile (x-y)was measured by a Paralell Plate Ava-lanche Counter (PPAC) placed in thecrossover point. A triple silicon telescope(∆E(20 µm)-E1(150 µm)-E2(150 µm))placed at zero degrees and a few centi-meters beyond the PPAC allowed theidentification of the atomic number,mass and the energy of the secondarybeam particles. Figure 2 shows thePPAC x-y spectrum obtained with the8Li secondary beam produced by thereaction 9Be(7Li,8Li).

Table 1.

(*)Production reactions measured at RIBRAS using only 1 solenoid.

Production reaction secondary beam (part/s/�Amp

9Be(7Li,8Li) (*) 106

9Be(7Li,6He) (*) 105

3He(7}Li,7Be)(*) 105

3He(6Li, n)8B 105

12C(17O,18mF) 103




The secondary beam spot mea-sured at the PPAC position wasabout 7 mm in diameter which isconsistent with a primary beam spotsize of 4–5 mm multiplied by a mag-nifying factor of 1.5 of the first sole-noid. Figure 3 shows the ∆E-Etelescope spectra with the solenoidtuned to select 8Li and 6He ionsrespectively. The production ratesmeasured at RIBRAS for these twoexotic ions were of 104 p/s and 105

p/s respectively with a 300 nAe ofprimary beam. One can observe thepresence of contaminants in the sec-ondary beam like 7Li2+ degraded pri-mary beam and light particles. Thesecontaminants can be eliminated bythe second solenoid using a degrader

in the crossover point. The operationof the second solenoid depends onthe installation of the secondaryscattering chamber that is under con-struction.

In conclusion, a double supercon-ducting 6.5T (5T.m) solenoid systemis installed at the Pelletron Laboratoryof the University of São Paulo to pro-duce secondary beams of radioactivenuclei. The two solenoids weremounted and tested on the 45B beamline of the Pelletron experimentalarea. The system began its operationusing only the first solenoid and the7Li primary beam of the 8MV PelletronTandem. Secondary beams of 8Li,7Beand 6He were produced. Experimentsusing these secondary beams are inprogress.

References 1. Progress in RIBRAS Radioactive Ion

Beams in Brasil Project, R. Lichtenthäler,A. Lépine-Szily, V. Guimarães, G. F.Lima, M. S. Hussein, Nuclear Inst. andMethods, A505 (2003) 612–615c.

2. Radioactive Ion Beams in Brasil(RIBRAS), R. Lichtenthäler, A. Lépine-

Figure 2. X-Y Position spectrum (PPAC) of the 8Li secondary beam.

Figure 3. Left panel: E-∆E spectrum of the 8Li secondary beam produced by the9Be(7Li,8Li)8Be reaction.Right panel: E-∆E spectrum of the 6He secondary beamproduced by the 9Be(7Li,6He)10B reaction.




Szily, V. Guimarães, G. F. Lima, M. S.Hussein, Brazilian Journal of Physics,33, no.2 (2003)294.

3. Ribras: Radioactive Ion Beams in Brasil,M. S. Hussein, Nuclear Physics News,9 (1999) 28.

4. F. D. Bechetti, M. Y. Lee, T. W. O’Donnell,D. A. Roberts, J. A. Zimmerman, J. J.

Kolata, V. Guimarães, D. Peterson,P. Santi, Nucl. Instrum. and Methods inPhys. Res., A422 (1999)505.

5. A radioactive beam facility using alarge superconducting solenoid, J. J.Kolata, F. D. Becchetti, W. Z. Liu, D.A. Roberts and J. W. Janecke, Nucl.Instrum. Meth., B40/41(1989) 503.

6. P. D. Zecher, A. Galonsky, S. J.Gaff, J. J. Kruse, G. Kunde, E.Tryggestad, J. Wang, R. E. Warner,D. J. Morrissey, K. Ieki, Y. Iwata, F.Deák, Á. Horváth, A. Kiss, Z. Seres,J. J. Kolata, J. von Schwarzenberg,H. Schelin, Phys. Rev., C57 (1998)959.



Query SheetQ1 AU: please call out figures/tables in textQ2 AU: City?




Introduction One current trend in most branches

of contemporary research is the adop-tion of large computing facilities, capa-ble of calculating models of everincreasing complexity. This is particu-larly true for Nuclear Physics, a disci-pline that has often prompted thedevelopment of new theoretical andnumerical methods that stimulated theadvance of computing machinery.

The need for better computationalhardware was recognized by the ECT*Board in 2003, with the decision tostart a joint program between the Isti-tuto Nazionale di Fisica Nucleare(INFN) [1], the Istituto Trentino di Cul-tura (ITC) [2], the Provincia Autonomadi Trento (PAT) [3], and Exadron [4],the High Performance ComputingDivision of the Eurotech [5] group.

The result of the cooperation is anadvanced computing infrastructure, cen-tered on a 1TFlop/s cluster and an inno-vative networking technology, especiallysuited for the exacting needs of a distrib-uted community of researchers.

One important aspect of the ECT*installation is the development of apioneering network technology thataims at improving the current state ofthe art in clustered computing. In fact,although–numerous commercial prod-ucts are already available (Infiniband,Myrinet, Quadrics, etc.), their generalpurpose design does not necessarily fitoptimally with the technical require-ments for scientific computing.

It is well known that lattice or meshcomputing have very specific dataaccess and transmission patterns that

reflect the relationship between adjacentnodes. Although many computationallyhard scientific problems are naturallymapped on such a computational model,most off-the-shelf networking productsare modeled on a switched architecturethat might not streamline the actual flowof information.

The technology developed by thepartners of the initiative and imple-mented at the computing facilityallows for a different approach at clus-tered networking that employs aswitchless, hardwired 3-D communi-cation mesh.

The deployment of the 1Tflop/s com-puting facility is at an advanced stage: thecluster is already in production, with stan-dard networking; the boards and softwarelayer for the new inter-node connectivitytechnology are under production and willbe installed shortly.

Finally, it should be remarked thatthe ultimate goal of the project is tobring the capabilities of the new facil-ity to a large number of users: soonafter the public opening of the system,a Call for Proposals will addressed toa broad spectrum of scientists. Thisinitial phase is expected to evolve nat-urally toward the participation to a“GRID,” or “GRID-like” environmentthat could allow the sharing of compu-tational power among an enlargedcommunity of researchers both fromAcademia and Industry.

Priorities The computing facility stems from

the need to fulfil a set of requirements

that are of significant interest for thescientific community:

1. To develop a novel network tech-nology, capable of overcoming thelimitation of the traditionalapproaches;

2. To provide a computing resourceadequate for the most advancedprojects;

3. To allow and promote the sharingof knowledge between a distrib-uted base of users, with particularattention for young researchers;

4. and, therefore, to qualify forbecoming a “GRID” node.

The primary goal of this installa-tion is to foster projects that arealigned with ECT* scientific activi-ties; however, it is open to projectsand initiatives belonging to differentdomains.

The other ambitious goal that wasset is the attempt to demonstrate that it ispossible to overcome the many obsta-cles that often separate Theoretical Sci-ence and Engineering. In fact, most ofthe traditional networking technologiesused in high-performance computerswere not designed having in mind thespecial needs of scientific computing.For this reason, ECT* decided tobecome the test-bed for a novel devicethat has been developed by the APEgroup of INFN and Exadron.

This new hardware derives from a10-year-long experience in the APEproject [6,7], one of the most success-ful European initiatives for the cre-ation of a series of massively parallel




supercomputers dedicated to latticecomputing. In particular, one peculiaraspect of the APE supercomputer ishow the inter-node communication isimplemented [8]. Now, a technologybased on the experience drawn fromthe APE project is going to be installedin the ECT* machine. This will allow asuperior performance in calculationswhere intense neighboring node com-munication is requested, besides beingvery competitive in general.

In this respect, a future, possibleparticipation to a “GRID” is per se animportant challenge: the open natureof this kind of infrastructure will, atleast in principle, allow the interactionand cooperation of many differentkind of entities. Therefore, it is funda-mental to establish a solid, yet flexibleframework, capable of allocating thediverse needs of a multifaceted com-munity.

System Description The current implementation of the

facility revolves around the clusterarchitecture. The following tables sum-marize the main technical features:

The system is currently runningFedora Core 2 [9], integrated with manyclustering tools. Although many inter-esting solutions for clustering exist(Rocks [10], Oscar [11], etc.) it waspreferred to use a stable, yet up-to-datedistribution upon which the necessaryinfrastructure could be deployed,therefore allowing for a better controlover the interaction of the differentcomponents.

Due to its experimental nature, itis possible that the overall configura-tion of the system might change overtime, in order to adapt to the evolu-tion of the networking technology.

From the user’s point of view, thesystem provides a rich set of facilitiesthat include:

• GNU [12] and other Open Sourcecompilers for the most commonlanguages (FORTRAN, C, C++,JAVA, etc.).

• Scientific and general libraries (MPI[13,14], ATLAS [15], BLAS [16],CERNLIB [17], FFTW [18], etc.).

• Job scheduling and administrationtools (Torque [19], Maui [20]).

• Hardware status monitoring (Gan-glia [21]).

• A number of applications onrequest by the users.

3-D Network Technology The novel 3-D inter-node connec-

tivity technology developed by the ini-tiative consists in a PCI-X boardcompatible with any standard serverthat provides 6 full-duplex channels.Each channel has a nominal speed of6.4 Gb/s for each direction with anoverall estimated latency of 6.3 µs

(preliminary drivers). This figureincludes the PCI bus latency; thismeans that the actual fabric latency isnegligible. The device is characterizedby three major functional blocks:

• The PCI-X interface. • The embedded crossbar switch. • The communication links.

Each board is connected to the 6neighboring nodes via differentiallinks, therefore implementing a 3-Dmesh of links. According to thisscheme, it is possible to establish adirect transmission with those nodesthat are actually interested in most ofthe communications occurring in a lat-tice/mesh calculation. The packetsdirected to other nodes are routed,thanks to the embedded crossbarswitch that relays them, to the nextboard. The cost of traversing a largemesh side-to-side is negligible andamounts to few clock cycles per nodetraversed (nanoseconds). Therefore, it

Figure 1. One example of the threecabinets composing the ECT* cluster.The computational units are encasedin a very compact blade format (up to20 CPUs in 3U).

Table 1. Overall features.

Computing nodes 96

File server nodes 3

Master node 1

Total peak performance (RPeak)

1.1 TFlop/s

Expected performance(RMax) (Gbit eth)

0.6 TFlop/s

Expected performance(RMax) (APE tech)

~0.8 TFlop/s

Total RAM capacity 100 GByte

Total Disk capacity 4 TB (internal) + 4.8 TB (external arrays)

Inter-node network (Gigabit Eth)

2 independent networks(MPI and filesystem)

Inter-node network (APE tech)

6-neighbor flexible topology

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is possible to effectively build aswitchless infrastructure (i.e., with-out a central switch or a tree ofswitches) that is highly optimizedtoward patterns of traffic that exhibitheavy local communications, with-out having to pay a penalty for non-local transmission.

Specific drivers have been devel-oped for the Linux kernel: both 2.4and 2.6 kernel series are supported.The MPI libraries are being recoded inorder to allow a smooth execution of

standard parallel codes on the system.While not yet complete, a subset ofthe functions provided by MPI isavailable: for instance, it is possible tocompile and run codes such as theHPL22 benchmark.

Projects and Opportunities Whereas a number of internal

projects are emerging, external proposalare most welcome and will be evaluatedby an ad hoc commission as soon as thecluster has been opened to the public.

For this reason, ECT* will stimu-late the participation to its high-performance computing initiative witha Call for Proposals addressed to abroad spectrum of scientists. Althoughthe main focus of the Centre isNuclear Physics and related areas, anyinnovative and computationally demand-ing project will be accepted for evalu-

ation: in particular, both theoreticaland applied proposals for GRID-relatedand/or interdisciplinary work will bewelcome.

Industrial Partnership It is worth mentioning the active

role that Exadron, one of the fewsupercomputer manufacturers inEurope, is having in this project. Infact, Exadron has devoted a signifi-cant amount of internal resources tothe development of the cluster facility.

Whereas most cluster installationsuse commodity hardware that has notbeen designed for scientific applica-tions, Exadron has developed a num-ber of crucial components specificallyfor the needs of the research community.

Moreover, Exadron is the indus-trial partner of the APE group, anotherkey player of the project.

Figure 2. Clockwise: the functional blocks of the inter-node communication board; one production board; a “naked”prototype board.

Table 2. Computing node features.

CPUs 2 × Xeon @2.80 GHz

RAM 1 GB

Local Disk capacity 40 GB

Network interfaces 2 × Gigabit eth + 1 × APE tech (6 channel)




The fruitful cooperation estab-lished with the ECT* High Perfor-mance initiative is going to have apivotal role in the development of anentire family of high performanceproducts, therefore demonstrating that

Technology Transfer is a real opportu-nity even for a centre mainly focusedon theoretical studies, as ECT* is.

The ECT* computing facility hasbeen named Ben in honor of Prof. BenMottelson, the first director of the Centre.

References 1. Istituto Nazionale di Fisica Nucleare

(INFN) – http://www.infn.it/ 2. Istituto Trentino di Cultura (ITC) –

http://www.itc.it/ 3. Provincia Autonoma di Trento (PAT)

– http://www.consiglio. provincia.tn.it/ 4. Exadron, the HPC Division of the

Eurotech Group – http://www.exad-ron.com

5. http://www.eurotech.it 6. http://apegate.roma1.infn.it/APE/

ape_main.html 7. http://www-zeuthen.desy.de/ape/html/ 8. http://www-zeuthen.desy.de/ape/html/

APEmille/Topology.php 9. Fedora Project—http://fedora.redhat.

com 10. http://www.rocksclusters.org/ 11. http://oscar.openclustergroup.org/ 12. GNU Free Software Foundation—

http://www.gnu.org 13. http://www-unix.mcs.anl.gov/mpi/ 14. http://www.lam-mpi.org/ 15. http://math-atlas.sourceforge.net/ 16. http://www.netlib.org/blas/ 17. http://cernlib.web.cern.ch/cernlib/ 18. http://www.fftw.org/ 19. http://supercluster.org/torque/ 20. http://www.clusterresources.com/

products/maui/ 21. http://ganglia.sourceforge.net/ 22. http://www.netlib.org/benchmark/hpl/

PIERFRANCESCO ZUCCATO

ECT* PostDoc, Italy

Figure 3. 3-D hardware mesh (only part shown for clarity). Each circlerepresents a computational unit. Each “tower” is a cabinet with 32computational nodes. Extremities are connected together with wrap-aroundlinks (not shown).

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Recent Achievements in Multinucleon Transfer Reaction Studies at LNL

Query SheetQ1 AU: publisher or editor missingQ2 ED: use photo placement



Recent Achievements in Multinucleon Transfer Reaction Studies at LNL

Introduction What makes the field of nuclear

reactions with heavy-ions so rich is thefact that the nucleus presents both thedegrees of freedom associated withthe single particle motion and thoseassociated with the strong surfacevibrations and rotations. In the lowenergy regime (close to the Coulombbarrier) it is the interplay of these twokinds of degrees of freedom that gov-erns the evolution of the reaction fromthe quasi-elastic to the more complexdeep-inelastic and fusion regimes. Thequasi-elastic reactions, where fewquanta are exhanged between targetand projectile, constitue the mostimportant tools for nuclear structureand reaction dynamics studies [1].From the stripping and pick-up of neu-trons and protons one can deduceinformations about the shell structureclose to the Fermi surface (one-parti-cle transfer) of the two reactants orone can study nuclear correlations inthe nuclear medium (multi-nucleontransfer reactions) [2–4]. Among thesecorrelations of particular importanceare the pairing one, that is, the abilityof two nucleons to form a pair withzero angular momentum [1,2].

Extensive work using differentheavy ion reactions has been performedduring last few years with the time-of-flight magnetic spectrometer PISOLO,installed at the Laboratori Nazionali diLegnaro (LNL) [5]. The variety of chan-nels that could be observed in severalexperiments allowed to follow in asystematic way the population pat-tern of the reaction products in theZ-A plane [6,7]. Parallel to this exp-erimental work, semi-classical models

have been implemented [8,9] that areable to treat quasi-elastic and deep-inelastic processes in terms of few andwell-known degrees of freedom and thatallow a quantitative comparison with theexperimental observables.

Multinucleon transfer reactionsconstitute also a valuable tool to popu-late neutron-rich isotopes, at least inspecific mass regions [10]. The studyof the lowest excited levels of neu-tron-rich nuclei is an area of increas-ing interest for the verification of thepredicted changes of the shell struc-ture and of the nucleon-nucleon corre-lations far from the β-stability valley.A very powerful technique for thesestudies is constituted by the couplingof large gamma arrays detectors withthe new generation of large solid anglespectrometers. At LNL the PRISMAheavy-ion magnetic spectrometer [11]coupled to CLARA [12] recentlyentered into operation.

Results from Inclusive Measurements with PISOLO

From the comparison between oneand two particle transfer processes onecan already learn a lot on the interplaybetween single-nucleon and pair-transfer modes, but it is only whenseveral number of nucleons are trans-ferred that one has a better view onhow the mechanism evolves. Anexample of a complete measurementperformed with PISOLO is that for the58Ni + 208Pb system [7]. The experi-mental total angle and Q-value inte-grated cross-sections for pure neutronpick-up and pure proton strippingchannels are reported in Figure 1 incomparison with the calculations

performed within the semiclassicalComplex WKB (CWKB) model (seeRef. [7] and references therein fordetails).

The experimental data show, forneutrons, a quite regular drop of thecross-sections as a function of thenumber of transferred nucleons, indi-cating that the transfer mechanism islikely to proceed as a sequence ofindependent single-particle modes.Similar results have been obtained atArgonne [13]. With the dotted line inFigure 1 we show the calculationsmade treating the transfer in a succes-sive approximation and consideringall the transitions as independent. Agood agreement with the data isobtained for all pure neutrons transferchannels and for the stripping of oneproton. However the calculation missesthe massive proton transfer channelsunderpredicting the two-proton strip-ping by an order of magnitude. Thediscrepancies indicate that the theoryshould incorporate more complextransfer degrees of freedom. By add-ing to the reaction mechanism thetransfer of correlated pairs of protonsand neutrons, in the macroscopicapproximation, and fixing the strengthof the formfactors to reproduce thepure −2p channel, one sees (dashedline) that the predictions for all othercharge transfer channels are muchbetter whereas no appreciable modifi-cations are visible for the neutrontransfer channels (dotted and dashedlines almost overlap with the full linein the right panel and are not shown).Because the pairing interaction has thesame strength for neutrons and pro-tons we kept the same form factors for




the +2n and −2p channels. The contri-bution of the pair mode for neutron isnegligible due to the fact that its effectis masked by the successive mecha-nism; notice, in fact, that the cross-section for the +1n channel is almost afactor ten larger than the one of −1pchannel. In multi-nucleon transfer chan-nels large energy losses are reached,therefore the final yield can be consid-erably altered by evaporation, mostlyneutrons. Including these evaporationeffects a much better prediction isobtained for the final cross-sections,as shown by the full line in Figure 1.The calculation includes the transi-tions among all the single particle lev-els of target and projectile of a fullshell below the Fermi surface and ofall the ones above. To see if thischoice of the shell model space isadeguate for these reactions we look atthe Total Kinetic Energy Loss (TKEL)spectra. In Figure 2 are shown TKELdistributions for the system 62Ni + 206Pb,

measured [6] at three bombardingenergies, for an angle close to thegrazing one.

Figure 2 shows that only the +1nand +2n channels have the main popu-lation concentrated in a narrow lowenergy region (close to the ground-ground state transition), and the theorygives a very good description, whereasfor more massive transfer channels thepopulations widen and shift towardmore negative Q-values developingtails that increase with the number oftransferred neutrons. This may indi-cate that, even for this system whereall neutron transfer pick-up channelsare at optimun Q-value, the “cold”transfers (associated with low excita-tion energy) are hindered by processesthat drive the population toward highexcitation energy. By looking at theangular distributions of the samechannels one sees that they display abell-shaped form (underlying the graz-ing character of the reaction) with a

width that increases with the numberof transferred particles in particular inthe forward direction.

These observations, both in theTKEL and angular distributions, indi-cate the relevance of the surfacedegrees of freedom. It is, in fact, thesurface dynamics, governed by thelow lying modes, that allows the twoions to stay in close contact for longertimes and thus to build up a “neck”between the two colliding partners.

Quite interesting expectations arecoming by looking at the Q-value dis-tributions of the 40Ca+ 208Pb reaction[14]. Figure 3 shows the TKEL distri-butions at three bombarding energiesfor the two-neutron pick-up channel incomparison with CWKB calculations.As can be appreciated, the two neutronpick-up channel displays at all measuredenergies a well defined maximum,which, within the energy resolution ofthe experiment, is consistent with adominant population, not of the groundstate of 42Ca, but of states with an exci-tation energy at around 6MeV. Fromthe theoretical calculations one can seehow the different single particle levelsare populated in the reaction. Theinspection of this population for the+2n channel tells us that the maximumof the distributions correspond to thetransfer of two neutrons in the p3/2

orbital; note that the single particleform-factors for the p3/2 orbital aremuch larger than the one for the f7/2

orbital that constitutes the main config-uration of the ground state of 42Ca. The(p3/2)

2 configuration corresponds to themain component of the excited 0+

states at around 5.4MeV of excitationenergy that were interpreted as multi(additional and removal) pair-phononstates [2]. These results open, at least inour expectation, the possibility to studymultipair-phonon excitations. The strongconcentration of strength near 6MeV

Figure 1. Total cross-sections for pure proton stripping (left side) and pureneutron pick-up (right side) channels for the indicated reaction. The lines arethe CWKB calculation.




of peculiar 0+ states for 42Ca (they mustcontain the (p3/2)

2 configuration) isclearly visible in the bottom part of Fig-ure 3, where the strength distributionS(E) coming from large scale shellmodel calculations is shown [14].

Measurements with the PRISMA Large Solid Angle Spectrometer

From the discussion in the lastsection it is clear that for the defi-nite assigment of the states ataround 6 MeV in 42Ca it would be

important to distinguish the popula-tion to specific nuclear states and todetermine both their strength distri-bution and decay pattern. This, infact, carries information on thewavefunctions of the populated lev-els and on the pairing correlation[1]. Experiments in this directionmust exploit the full capability ofspectrometers with solid anglesmuch larger than the conventionalones, and with A, Z, and energy res-olutions sufficient to deal also withheavy mass ions. This is now pos-sible with the PRISMA spectrome-ter [11] designed for the A = 100–200, E = 5–10 MeV/amu heavy-ionbeams of the accelerator complex ofLNL. First experiments on heavy-ions grazing collisions have beenalready performed with beams inthe A = 40–90 range. One of thepresent interests are nuclear struc-ture studies of neutron-rich nuclei,populated at relatively high angularmomentum, by means of binaryreactions. These studies are per-formed by combining PRISMA withthe CLARA gamma-array [12],recently installed close to the targetpoint and consisting of an array of24 Clover detectors from theEuroball collaboration. With stablebeams and at the energies and inten-sities typical of tandem accelera-tors, one can presently reach regionsmoderately far from β-stability (onaverage 3–5 nucleons from the laststable isotope), but one can investi-gate nuclei through the entirenuclear chart, provided suitable pro-jectile/targets are chosen.

An exploratory run withPRISMA+CLARA has been veryrecently done by using the reaction90Zr + 208Pb with the main aim of look-ing at the yield production of specificQ-value ranges in the Zr and Sr

Figure 2. Experimental (histograms) and theoretical (lines) total kinetic energyloss (TKEL) distributions for pure neutron pick-up and proton strippingchannels in the reaction 62Ni + 206Pb. The ground-ground state Q-values areindicated by the down arrows (see Ref. [6] for details).




isotopes close to the expected regionwhere pair vibrational modes may beexcited. The spectrum in Figure 4shows an example of the obtainedmass resolution in such a reaction atElab = 560 MeV. One observes eventscorresponding to the pick-up as wellas stripping of neutrons. The right side(left side) are the spectra obtainedwith (without) gamma coincidences.

One observes different relative yieldsin mass spectra for each isotope, dueto the different gamma multiplicitiesfor the various multinucleon transferchannels populated in the reaction. Inthe bottom part is shown, as an exam-ple, the coincident gamma spectrumfor 90Zr, obtained after Doppler cor-rection for the projectile-like nucleiselected by the spectrometer. In gen-eral, the Zr isotopes span a range fromspherical to highly deformed shapesand it would be therefore interestingto investigate in detail the change ofthe population strength and decay pat-tern properties of specific levels pop-ulated via multinucleon transfermechanism.

Acknowledgments In this report we have presented

the results of the collaboration with

the following people: S. Beghini,E. Fioretto, A. Gadea, G. Montagnoli,F. Scarlassara, A. M. Stefanini,S. Szilner, M. Trotta. The third sec-tion involves the whole PRISMA-CLARA collaboration.

References 1. A. Bohr and B. Mottelson, Nuclear

Structure, Vol. I, edited by W. A.Benjamin, Inc., New York (1969).

2. R. A. Broglia, O. Hansen, and C. Riedel,Advances in Nuclear Physics, editedby M. Baranger and E. Vogt, Plenum,New York, 1973, Vol. 6, p.287.

3. C. Y. Wu, W. von Oertzen, D. Cline,and M. Guidry, Annu. Rev. Nucl. Part.Sci. 40, (1990) 285.

4. K. E. Rehm, Annu. Rev. Nucl. Part.Sci. 41, (1991) 429.

5. G. Montagnoli et al., Nucl. Instr. andMeth. in Phys. Res. A454, (2000) 306.

6. L. Corradi etal., Phys. Rev. C63, (2001)021601R.

Figure 3. Experimental (histograms)and theoretical (curves) total kineticenergy loss distributions of the twoneutron pick-up channels at theindicated energies. The arrowscorrespond to the energies of 0+

states in 42Ca with an excitationenergy lower than 7 MeV. Bottompanel shows the strength functionS(E) from shell model calculations(see Ref. [14] for details).

Figure 4. Panels (a) and (b) : mass distributions for Zr isotopes obtained in the90Zr + 208Pb reaction at Elab = 560 MeV and at θlab = 540, without (a) and with (b)gamma coincidences. Panel (c): single gamma spectrum of 90Zr. The peak at2186 keV corresponds to the lowest 2+ – 0+ transition.

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7. L. Corradi et al., Phys. Rev. C66,(2002) 024606.

8. A. Winther, Nucl. Phys. A572, (1994)191; Nucl. Phys. A594, (1995) 203.

9. G. Pollarolo and A. Winther, Phys.Rev. C62, (2000) 054611.

10. The EURISOL Report, Key experi-ment task group, J. Cornell, ed.,GANIL, Dec. 2003; http:/ /www.ganil.fr/eurisol.

11. A. M. Stefanini et al., Propostadi esperimento PRISMA, LNL-INFN (Rep)—120/97 (1997); A. M.Stefanini et al., Nucl. Phys. A701,(2002) 217c.

12. A. Gadea et al., Eur. Phys. J. A20,(2004) 193.

13. C. L. Jiang et al., Phys. Rev. C57,(1998) 2393.

14. S. Szilner et al., Eur. Phys. J. A21,(2004) 87.

LORENZO CORRADI

INFN-Laboratori Nazionalidi Legnaro

Legnaro (Padova), Italy

GIOVANNI POLLAROLO

Dip. di Fisica Teoricadell’Universita’ and INFN

Torino, Italy

L. Corradi (left) and G. Pollarolo (right).

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meeting reports


Atomic Nuclei at the Extreme Values of Temperature, Spin, and Isospin, XXXIX Zakopane School of Physics, 31 August–5 September 2004, Zakopane, Poland

In 2004 the XXXIX ZakopaneSchool of Physics (31 August–5September, http://chall.ifj.edu.pl/~maj/Zakopane2004/) was organized byAdam Maj from the Instytut FizykiJadrowej PAN in Krakow as a fiveday International Symposium. Theprogram was concentrated on thenuclear structure problems in nuclei atextreme values of temperature, spin,and isospin. The meeting was alsointended to celebrate, on the occasionof his 60th birthday, the remarkableachievements of Rafal Broda, a pio-neer in study of neutron rich nucleiwith gamma spectroscopy from deepinelastic collisions.

The meeting gathered 120 partici-pants from 15 countries to discuss in avery relaxed and excellent atmospherethe state of the art of the nuclear struc-ture research and the projects under-way for future activities. Whereas theoverviews of the different topics in thefield were given by the invited lec-tures and seminars, the selectedshorter contributions complementedvery well the discussion started by thelonger talks. It is important to stressthat several presentations were givenby bright young researchers and grad-uate students demonstrating very highcapabilities from which the commu-nity will surely benefit for present andfuture projects. In addition, physicistscould discuss together more infor-mally in the afternoons either bystrolling around or by taking part inthe organized hiking excursions on thevery panoramic trails in the moun-tains. Both for high scientific quality

and for the organization in general theZakopane School has been alwaysvery well recognized by the interna-tional community. This is testified toby the fact that several participants inthis meeting have also attended manyof the others of this series in the past.

The symposium was opened thefirst evening by A. Budzanowski(director of IFJ PAN Krakow) with alecture on phase transitions in highlyexcited nuclei reviewing the differentexperimental signatures pointing tothe observation of the liquid-gasphase transition of expanding nuclearmatter.

In the following four days thesymposium was chaired by four con-veners, Bent Herskind for the nuclei athighest spin, myself for nuclei at hightemperatures, Hans-Juergen Woller-sheim for exotic nuclei investigatedwith radioactive beams, and BogdanFornal for neutron-rich nuclei studiedwith stable beams.

The program of the session onnuclei at the highest spins was mainlyconcentrated on the impressive resultsobtained with the large arrays Euroballand Gammasphere. It is important tostress that these arrays were designedand constructed after the first and verysuccessful activity in the field of highspins led by Frank Stephens, BentHerskind, and Peter Twin—the lasttwo awarded this year with the LiseMeitner prize for nuclear science. Thehighlight on the key question ofextreme deformations are the newfindings of very large deformations inthe light and medium mass nuclei

(presented by W. Meczynski and P.Fallon), of the superdeformed triaxial-ity and wobbling motion (presented byG. Hagemann). In addition interestingresults were obtained for high-K struc-tures at extreme conditions (presentedby P. Walker), research of interest alsowith radioactive beams. The progressmade in the understanding of the struc-ture of shell-stabilized highly rotatingheavy nuclei has been discussed byT.L. Khoo while that chirality in rota-tion was presented by J. Srebrny. Par-ticularly interesting has been thediscussion on the search of hyperde-formed configurations that was trig-gered by the theoretical talk of J.Dudek and by the experimental talksof H. Huebel and Nyako illustratingthe different results from severalexperiments. The problem of hyperde-formation is still open and we can saythat we are in a situation similar tothat we had at the beginning of the1980s for the problem of superdefor-mation, namely some signals from thequasi continuum are present whereasthe indications from discrete lines arevery weak. Therefore it is clear to thecommunity that it is important to pur-sue this research in the future withmore efficient and selective arrays likeAGATA and GRETA. The status ofthese new arrays, designed and sup-ported first by the European and sec-ond by the American scientists, hasbeen presented by J. Simpson.

The session on nuclei at high tem-perature focused on the study of high-lying collective modes built on boththe ground state and on hot rotating


meeting reports


nuclei. The overview of the work onthe electric dipole strength below thegiant dipole resonance, based on theextensive work made at the Universityof Darmstadt, was given by J. Enderswho pointed the interest in this topicin connection with neutron rich nucleiformed at the radioactive beam facili-ties. The status on the problem of thenuclear compressibility as obtained bythe isoscalar monopole and dipolegiant resonances has been presentedby Y. Lui whereas new results onspin-isospin giant resonances wereillustrated by A. Krasznohorkay. Thefuture perspectives are related to theactivity with radioactive beams andin particular at GSI a construction ofa dedicated set up with a gas jet tar-get is in progress (R3B and EXELprojects).

The new achievements in the fieldof nuclear structure at finite tempera-ture have been discussed in connec-tion with two different aspects. Thefirst concerns the rotational dampingand selection rules in the order to chaostransitions (S. Leoni) whereas the sec-ond concerns the gamma-decay ofthe giant dipole resonance in excitednuclei (F. Camera, M. Kicinska-Habior,F. Gramegna, and M. Kmiecik). Recentdata on the giant dipole resonance inexcited nuclei have provided a betterunderstanding of the damping mecha-nisms at finite temperature and of theisospin mixing.

In particular, the role of nucleardeformation in the dipole response atvery high spins close to the fission limithas been investigated with Euroballexperiments. New indications of theoccurrence of the Jacobi shape transition(oblate–prolate) were found, transitionthat is also typical of gravitationalobjects rotating synchronously.

The session on exotic nuclei stud-ied with radioactive beams was

opened by T. Otsuka illustrating thenew shell model predictions on theevolution of shell and collective struc-tures in exotic nuclei. His results welldescribe the latest experiments at theRIB facilities and represent a usefulguide for the future experimental pro-grams. The status of the RISING facil-ity at GSI has been presented givingboth technical details (P. Bednarczyk)and the preliminary results of the firstexperiments (P. Reiter). These experi-ments concern the measurements ofthe B(E2) with Coulomb excitationand the study of isospin mixing inmirror nuclei using second fragmenta-tion reactions. Similar and comple-mentary activity on nuclear structurewith fast exotic beams at lower ener-gies is carried out at MSU and themain results were presented byA. Gade. The latest achievements con-cern nuclei in the vicinity of theN = Z = 28 nucleus 56Ni a benchmarkfor the study of nuclear shells. Awealth of information on heavy neu-tron rich nuclei characterized by thepresence of several isomeric states hasbeen obtained with decay studies withstopped relativistic radioactive beams(Z. Podolyak). This research will befollowed using the RISING set upfocusing also on the interesting prob-lem of the shape coexistence. On thesame topic of the shape coexistencewas the presentation of A. Goergenwho reported on new investigations atGANIL on Krypton isotopes. Theactivity carried out at Oak Ridge withradioactive beams of ISOL type withfew MeV/u has been presented byR. Grzywacz and K. Rykaczewski. Theyfocused on Coulomb excitation mea-surements of “pure” beams of fissionfragments such as the semimagic 82Geand doubly magic 132Sn, sub barrierfusion and proton decay. Progress in thecalculation techniques (K. Pomorski) on

shell model in this mass region is alsobeing made.

The session on the neutron richnuclei investigated with stable beamswas dedicated to Rafal Broda. Thissession was particularly lively andthe lecturers (P. Daly, S. Lunardi,P. Regan, R. Janssens) made an excel-lent job in recalling how the techniquebased on deep inelastic collision wasintroduced by Rafal and how it thenevolved with time. P. Daly pointed outthat “scavenging pays” because in thisway Broda and Fornal obtained verysuccessful results. Nuclear structureprograms using deep inelastic reac-tions have been carried out in differentlaboratories with the Gasp, Euroball,and Gammasphere arrays and manyresults obtained in different massregions as those on 68Ni and 50Ca (pre-sented by R. Broda) are at the basis ofthe current work with radioactivebeams. The present and near futureexperiments are searching for moreexotic nuclei and for short lived statesat higher spin and they are carried outat the PRISMA-CLARA set up atLNL and at Argonne with Gammas-phere equipped with the Chico particledetector.

The overview of the study of octu-pole deformations, of the rotatingheavy nuclei as, for example, Nobe-lium and in general all the challengesfor studying needles in a haystack werepresented by P. Butler. He also pointedout the importance for second-genera-tion radioactive beams of ISOL type asSPES at LNL, ISOLDE at CERN,SPIRAL2 at GANIL, and the EuropeanEURISOL project. These projects areall related to high-intensity beams.Beam of higher intensities are neces-sary also in the case of stable beams asit was discussed by F. Azaiez in orderto make a substantial progress in thesearch of hyperdeformation, in the


meeting reports


study of spinning very heavy nucleiand of nuclei around 100Sn.

The symposium also includedanother event, namely the Ceremonyof awarding the Diploma of the 2003Zdzislaw Szymanski Prize to MarekPfutzner who gave a very good lecture

on the current status of two-protonemission.

A March 2005 issue of Acta PhysicaPolonica B with the proceedings ofthe conference is in preparation. Thenext Zakopane School of Physics isplanned for September 2006.

After such a successful symposium Ihave only two closing remarks: thanksto Adam Maj for his excellent work andhappy birthday to Rafal Broda!

ANGELA BRACCO

Universita’ di Milano and INFN

Symposium on “Atomic High-Precision Mass Spectrometry”

Like only a few other parametersthe mass is a characteristic nuclearproperty. Each nuclide comes with itsown mass value different from all oth-ers (presently about 3,200 known orestimated) [1]. Thus the atomicmasses are basic quantities of highestinterest. High-accuracy mass mea-surements allow to determine nuclearand atomic binding energies and thushave a huge field of application thatextends beyond nuclear physics [2]. Inthe case of short-lived exotic atomicnuclei it ranges from the verificationof nuclear models to a contributiontowards the test of the StandardModel, in particular with regard to theweak interaction and the unitarity ofthe Cabibbo-Kobayashi-Maskawa quarkmixing matrix. As for mass measure-ments on stable atoms, they now reacha relative mass uncertainty of about10−11. This extreme accuracy allows,among others, to contribute to metrol-ogy, that is, the determination of fun-damental constants and a new definitionof the kilogram, and to tests of quan-tum electrodynamics and Einstein’senergy-mass relation [3].

Several of these topics have beenhighlighted recently at a symposiumon “Atomic High-Precision Mass Spec-trometry” (http://www.dpg-tagungen.de/prog/syam/index.html) in the frame-work of the annual meeting of the

German Physical Society. Eight dis-tinguished international speakers fromleading groups gave reviews andupdates of important aspects of thefield. The two sessions, each of fourtalks, have been moderated by E. W.Otten and G. Werth from the Univer-sity of Mainz. Several short talks ofyoung researchers have been added. Inthe following, we summarize theinvited talks, which gave an excellentoverview of this very active field.

Georges Audi of the CSNSM atOrsay started the symposium with “TheHistory of Mass Spectrometry and theAtomic-Mass Evaluation.” He drew themain lines from the early days of massspectrometry when Aston and Thom-son discovered isotopism, to the devel-opment of Mattauch-Herzog massspectrometers in 1930s, and to the firstinstallation of a high-precision Penning-trap mass spectrometer in 1986. Afterthis historical account he developedgeneral ideas about data evaluation innuclear physics and described the mostprominent features of the Atomic-MassEvaluation (AME), the reasons for itscomplexity, and how problems are facedand solved. He explained why it wasfound essential to create the NUBASEevaluation and how he finally succeededin having AME and NUBASE co-ordinated and published for the firsttime together in December 2003 [1].

Although the systematic survey of allavailable data is an essential part of thenuclear-mass business, this data is ofexperimental origin, and thus has to bemeasured. H.-Jürgen Kluge of GSI atDarmstadt and the University of Heidel-berg explained how to perform “High-Precision Mass Measurements on Radio-nuclides in Storage Rings and Ion Traps.”He noted that in the last decade new ideashave been introduced for high-precisionmass measurements of short-lived radio-nuclides that use the principle of ion trap-ping and cooling [4]. The new methodswere pioneered on the small scale of iontraps by the triple-trap mass spectrometerISOLTRAP [5,6] at ISOLDE/CERN,and on the large scale of storage rings bythe Schottky and isochronous mass spec-trometry at the experimental storage ringESR at GSI/Darmstadt [7,8]. In the meantime, a large fraction of all directly mea-sured masses in the chart of nuclei havebeen determined by these devices, andacross the world many other Penning-trap facilities at accelerators are opera-tional, in the building-up stage, orplanned. The talk motivated and intro-duced the large variety of atomic andnuclear physics experiments with storedparticles in ion traps [4].

In the following presentationGeorg Bollen from the National Super-conducting Cyclotron Laboratory atMichigan State University/East Lansing,


meeting reports


took that ball and reported about “Preci-sion Mass Spectrometry of Rare Isotopesin America.” He again emphasized thataccurate masses of nuclides far awayfrom the valley of beta-stability are mostimportant for the understanding of thenuclear many-body system as input forthe modelling of the synthesis of the ele-ments in the universe, and for tests offundamental symmetries. Because Pen-ning-trap mass spectrometry offersunprecedented accuracy and a very highsensitivity, in America, too, several Pen-ning-trap mass spectrometers have beenor are presently being built. Theseprojects make use of unique rare-isotopeproduction facilities and thus contributeto the worldwide effort to enhance theknowledge of nuclear binding energies[9]. The talk gave an overview of ongo-ing activities and the perspectives ofreaching even more exotic nuclides: TheCanadian Penning Trap mass spectrome-ter at Argonne recently started its experi-mental program [10]. LEBIT at theMichigan State University [11] andTITAN at TRIUMF/Vancouver [12] arein commissioning phase or under con-struction, respectively.

Although direct mass measure-ments built the data basis, theoreticalmodels are as important when itcomes to predict unknown nuclearmasses far away from the valley ofstability that are not (yet) in experi-mental reach. Piet Van Isacker fromGANIL at Caen discussed the “Theoryand Predictability of Nuclear Masses.”He reviewed the status of modernnuclear mass formulas [2]. Thisincludes the elementary Weizsäckerliquid-drop formula and its refine-ments, such as the finite-range dropletmodel, as well as more microscopicallyfounded attempts based on Hartree-Fock theory and the shell model. Spe-cial attention was paid to the recentsuggestion that there might be a limit

to the accuracy with which nuclearmasses can be calculated in a mean-fieldapproach and that chaotic motion insidethe atomic nucleus is responsible for thislack of predictability [13,14]. In view ofthe important implications of this claim,for example, for nuclear astrophysics, itsmeaning was clarified with an empiricalstudy of more than 2,000 nuclear masses.By use of Garvey-Kelson relations corre-lations among neighboring masses havebeen established where the root-mean-square deviation is below 100keV. Thiscan be considered as a upper limit for thecurrent predictability of nuclear masses.

The afternoon session started offwith “Recent Trends in the Determi-nation of Nuclear Masses” by JuhaÄystö of the University of Jyväskylä,Finland. He reminded all participantsthat the mass of a nucleus is a mirrorof its binding energy [2]. It is theresult of the strong interaction actingin the finite many-body system of pro-tons and neutrons, and thus carriesfundamental information on themicroscopic structure of the nucleus.The measurement of binding energieswith relative accuracies in the rangefrom 10−6 to 10−8 is necessary tounravel the predicted new phenomenain nuclear structure of exotic nucleiwith extreme proton to neutron num-ber ratios [15,16]. Precision measure-ments of nuclear masses also play animportant role in nuclear astrophysicsand fundamental symmetries andinteractions [17–19]. The talk pre-sented recent trends and in particularsome precision mass measurements ofexotic nuclei with high neutronexcess, which are of interest for stud-ies of the nuclear structure and theshapes of nuclei, as well as measure-ments of neutron-deficient nuclei ofinterest with respect to nucleosynthe-sis in stellar processes [20]. These mea-surements have become possible only

recently due to the employment of Pen-ning traps coupled to fast injection ofions. Selected results were taken fromthe ISOLTRAP facility at CERN andthe JYFLTRAP-IGISOL facility [21] atthe University of Jyväskylä.

After this talk the subject changedfrom mass spectrometry on radionuclidesto high-precision mass measurements onstable ions. Reinhold Schuch of theStockholm University reported on massmeasurements with the SMILETRAPPenning-trap mass spectrometer, “A Pre-cision Mass Balance Using HighlyCharged Ions.” It exploits the merits ofhighly charged ions retrapped from anelectron-beam ion source. These ions areretarded in a first cylindrical Penning trapbefore a fraction of them is sent to thehyperbolic precision Penning trap wheretheir cyclotron frequency is measuredwith a resolving power of 108 [22]. Inorder to reduce the influence of mag-netic-field variations the cyclotron fre-quencies of ions of interest and that of thereference ions are measured within dura-tions as short as two minutes. Severalmass measurements with a relativeuncertainty in the region of 0.3 to a fewppb have been performed by use of ionswith charge states 1+ to 52+ [22]. Thenuclides investigated include 28,30Si for anew definition of the kilogram and the76Ge-76Se pair [23] to extract the Q valueof double-beta decay for the search ofneutrinoless double-beta decay.

Edmund Myers from Florida StateUniversity reported about “PrecisionMass Spectrometry with One and TwoIons in a Penning Trap,” which hadbeen pioneered by David Pritchard atMIT. In the 1990s Prichards groupdeveloped a Penning-trap setup andestablished an atomic mass table withapplication to fundamental constantsin a class of its own, namely at anuncertainty level of 10−10 [24]. Thesuccess of this mass spectrometer is


meeting reports


based on several special features suchas a dc-SQUID detector and the use ofa “pulse and phase” technique, analogousto the Ramsey Separated-Oscillatory-Field method. In the last few years anfurther technique has been developed:The two ions to be compared are posi-tioned in the same trap in a coupledmagnetron orbit. Their cyclotron fre-quencies are thus measured simulta-neously. This method suppresses theuncertainty due to, for example mag-netic-field fluctuations by two to threeorders of magnitude and allowed masscomparison with uncertainties as lowas 7 × 10−12 [3]. It led to the discoveryof rotational state-dependent polariza-tion-induced cyclotron-frequency shiftsand a new test of Einstein’s E = mc2.In 2003 the mass spectrometer wasrelocated to Florida State University atTallahassee where additional massmeasurements at the 10−10 level usingsingle-ion techniques have been com-pleted. Further development of thesub-10−11 two-ion technique is inprogress, in particular for a high-pre-cision atomic-mass comparison of tri-tium/helium-3, which will be relevantto neutrino-mass research.

Finally, the series of symposiumtalks was completed by Gerald Gabrielseof the University of Harvard who ext-ended the range of applications to“Highly Accurate Measurements of Par-ticle and Antiparticle Masses.” He pre-sented a number of fundamental testsvia mass and charge-to-mass ratio com-parisons including one of the most strin-gent test of the most fundamentalsymmetry of physics, namely CPT[25,26]. The mass comparison has beenperformed for both positrons versuselectrons, that is leptons, and for anti-protons versus protons, that is, hadronicmatter. Furthermore, the audience wasreminded that ion trapping and in par-ticular the Penning trap is not

restricted to precision measurementsof atomic masses. One particularlyexciting aspect is the combination ofpositron and antiproton trapping. Thisrecent development led to the creationof neutral antimatter in the form ofantihydrogen by the “recombination”of simultaneously trapped antiprotonsand positrons [27–30].

More than 7,000 physicistsattended this year’s annual meeting ofthe German Physical Society at Berlin.They brought more than 5,000 contri-butions in the form of talks and post-ers. The symposium on “AtomicHigh-Precision Mass Spectrometry”was certainly a highlight.

References 1. G. Audi etal., Nucl. Phys. A 729 (2003) 3. 2. D. Lunney, J. M. Pearson, C. Thibault,

Rev. Mod. Phys. 75 (2003) 1021. 3. S. Rainville, J. K. Thompson, D. E.

Pritchard, Science 303 (2004) 334. 4. H.-J. Kluge et al., Physica Scripta

T104 (2003) 167. 5. K. Blaum et al., Nucl. Instrum. Meth. B

204 (2003) 478. 6. F. Herfurth etal., J. Phys. B 36 (2003) 931. 7. T. Radon et al., Nucl. Phys. A 677

(2000) 75. 8. H.-J. Kluge, K. Blaum, C. Scheidenberger,

Nucl. Instrum. Methods A 532 (2004) 48. 9. G. Bollen, Lect. Notes Phys. 651

(2004) 169. 10. J. Clark et al., Phys. Rev. Lett. 92

(2004) 192501. 11. S. Schwarz et al., Nucl. Instrum. Meth.

B 204 (2003) 507. 12. J. Dilling et al., Nucl. Instrum. Meth. B

204 (2003) 492. 13. O. Bohigas and P. Leboeuf, Phys. Rev.

Lett. 88 (2002) 092502. 14. S. Åberg, Nature 417 (2002) 499. 15. J. Van Roosbroeck et al., Phys. Rev.

Lett. 92 (2004) 112501. 16. S. Rinta-Antila et al., Phys. Rev. C 70

(2004) 011301(R). 17. K. Blaum et al., Phys. Rev. Lett. 91

(2003) 260801. 18. M. Mukherjee et al., Phys. Rev. Lett.

93 (2004) 150801.

19. A. Kellerbauer et al., Phys. Rev. Lett.93 (2004) 072502.

20. D. Rodríguez et al., Phys. Rev. Lett. 93(2004) 161104.

21. V. Kolhinen et al., Nucl. Instrum.Meth. A 528 (2004) 776.

22. I. Bergström et al., Nucl. Instrum.Methods A 487 (2002) 618.

23. G. Douysset et al., Phys. Rev. Lett. 86(2001) 4259.

24. M. P. Bradley et al., Phys. Rev. Lett. 83(1999) 4510.

25. G. Gabrielse et al., Phys. Rev. Lett. 82(1999) 3198.

26. G. Gabrielse, Adv. At. Mol. Opt. Phys.45 (2000) 1.

27. M. Amoretti et al., Nature 01096(2002) 1.

28. M. Amoretti et al., Nucl. Instrum.Methods A 518 (2004) 679.

29. G. Gabrielse et al., Phys. Rev. Lett. 89(2002) 213401.

30. M. H. Holzscheiter, M. Charlton,M. M. Nieto, Phys. Rep. 402 (2004) 1.

KLAUS BLAUM

Johannes Gutenberg-UniversitätMainz Germany

LUTZ SCHWEIKHARD

Ernst-Moritz-Arndt-UniversitätGreifswald Germany


meeting reports


Report on the 15th Panhellenic Symposium on Nuclear Physics

This year the annual symposium ofthe Hellenic Nuclear Physics Societywas held on May 27 and 28 at thePhysics Department of the AristotleUniversity of Thessaloniki.

In the Symposium the most recentwork of Greek nuclear physicists,working within or out of Greece, wasreported. There were also invitedspeakers from abroad, as it is a tradi-tion of the Society to invite distin-

guished foreign colleagues. More than75 participants from 5 countriesattended the meeting. The large partic-ipation of young colleagues at theM.Sc. and Ph.D. levels should be par-ticularly noticed.

There were 40 talks coveringmany areas from Nuclear Structureand Reactions to Nuclear Astrophys-ics and Heavy Ion Physics and relatedareas.

This year, the guest of honor wasProfessor Dr. Peter Ring from the Phys-ics Department of the Technical Univer-sity of Munich. The Hellenic NuclearPhysics Society honored Professor Ringfor his pioneering work in the nuclearmany body problem and named him ahonorary member of the Society.

GEORGIOS A. LALAZISSIS

Chair of the Organizing Committee


news and views


IBA-Europhysics Prize 2005 for “Applied Nuclear Science and Nuclear Methods in Medicine”

The Executive Committee of theEPS has approved the recommendationof the Nuclear Physics Board accordingto the proposal of the IBA-EPS prizeselection Committee to award the IBA-Europhysics Prize 2005 to Prof. Dr.Werner Heil, Johannes Gutenberg Uni-versität Mainz, Germany and Dr. PierreJean Nacher, Laboratoire Kastler Bros-sel, ENS Paris, France. The Prize isattributed with the citation: “For thedevelopment of spin polarized 3He tar-gets by optical pumping and their appli-cations in nuclear science andmedicine: nuclear physics, neutron lowtemperature physics and medicine.”

The two winners are pioneers inthe art of polarizing 3He by themethod of metastability exchangeoptical pumping (MEOP) and apply-ing it to several fields (electron scat-tering on polarized 3He targets,polarization of neutron beams, con-trast agent for NMR tomography).Powerful techniques of polarizing 3He

have been developed in the past forfundamental experiments in nuclearand neutron physics. The basis for animportant application in medicine wasprepared, the use of polarized 3He asa contrasts agent to image the air-spaces of the lungs and to check lungfunctions.

The IBA-Europhysics prize issponsored by the IBA (Ion BeamApplications) Executive Committee,Chemin du Cyclotron, 1348 Louvainla Neuve, Belgium. It will be deliv-ered during the XIX Nuclear PhysicsDivisional Conference “New Trendsin Nuclear Physics Applications andTechnology” in Pavia, Italy fromSeptember 5–9, 2005.

PROF. CH. LECLERCQ-WILLAIN

President IBA-EPS Selection CommitteeUniversité libre de Bruxelles,

B 1050 Bruxelles

PROF. DR. WERNER HEIL

DR. PIERRE JEAN NACHER


calendar


2005 March 11–12

MPI Heidelberg, Germany. “NewTrends in Nuclear, Atomic andMolecular Physics.”

Web: http://www.mpi-hd.mpg.de/heavy-ion/65/

March 13–20 Bormio, Italy. XLIII International

Winter Meetings on Nuclear Physics.Web: [email protected]

March 19–23 San Servolo, Italy. FUSION06,

International Conference on ReactionMechanisms and Nuclear Structureat the Columb Barrier.

Web: http://www.lnl.infn.it/~fusion06/

March 29–April 1 Kloster Banz, Bavaria, Germany.

Neutron-Rich Radioactive IonBeams—Physics with MAFF.

Web: http://www.ha.physik.uni-muenchen.de/maff/workshop/

May 16–20 Debrecen, Hungary. Nuclear Phys-

ics in Astrophysics—II. Web: http://atomki.hu/~npa2/

May 16–22 Bonn, Germany. International

Conference on Low Energy Antipro-ton Physics (LEAP-05).

Web: http://www.fz-juelich.de/leap-05

May 23–26 Bonn, Germany. 6th International

Conference on Nuclear Physics atStorage Rings STOR105.

Web: http://www.fz-juelich.de/ikp/stori05/

May 27–31 Aschaffenburg, Bavaria,

Germany. SHIM 2005: Swift HeavyIons in Matter.

Web: http://www.gsi.de/SHIM2005

June 14–18 Lund, Sweden. International Con-

ference on Finite Fermionic Systems,Nilsson Model 50 years.

Web: http://www.matfys.lth.se/Nilsson

June 20–25 Debrecen, Hungary. Exotic

Nuclear Systems ENS’05. Web: http://atomki.hu/~ens05/

June 28–July 1 Peterhof, St. Petersburg, Russia.

LV International Meeting on NuclearSpectroscopy and Nuclear Structure“Frontiers in the Physics of Nucleus.”

Web: http://nuclpc1.phys.spbu.ru/nuclconf

August 30–September 6 Piaski, Poland. XXIX Mazurian

Lakes Conference on Physics:“Nuclear Physics and the Fundamen-tal Process.”

Web: http://zfjavs.fuw.edu.pl/mazurian/mazurian.html

September 5–9 Pavia, Italy. EPS XIX Nuclear

Physics Divisional Conference(NPDC19).

Web: http://www.pv.infn.it/~npdc19

September 10–14 Zaragoza, Spain. Ninth Interna-

tional Conference on Topics in Astro-particle and Underground Physics(TAUP).

Web: http://www.unizar.es/taup2005

September 12–16 Caen, France. 11th International

Conference on Ion Sources ICIS05. Web: http://www.ganil.fr/icis05

September 12–17 Kos, Greece. Frontiers in Nuclear

Structure, Astrophysics, and Reac-tions Conference (FINUSTAR).

Web: http://www.inp.demokritos.gr/~finustar

October 3–7 Igazu, Argentina. The Sixth Latin

American Symposium on NuclearPhysics and Applications.

Web: http://www.tandar.cnea.gov.ar/misc/SLAFNAP6.php

October 16–22 Dresden, Germany. Workshop on

Critical Stability. Web: http://www.mpipks-dresden.

mpg.de

October 17–21 Beijing, China. Asia-Pacific Sym-

posium on Radiochamistry 2005APSORC-05.

Web: http://www.ihep.ac.cn/apsorc2005

December 15–20 Honululu, Hawaii, USA. “SCI-

ENCE WITH RARE ISOTOPEBEAM.” Part of PACIFICHEM2005.

Web: http://www.phy.cuhk.edu.hk/gee/pachem05/pacifichem.html

2006 September 2–6

Rio de Janeiro, Brazil. Interna-tional Conference on Nucleus-Nucleus Collisions NN2006.

Web: [email protected]


calendar


Second Announcement

Call for Abstracts

Asia-Pacific Symposium on Radiochemistry 2005(APSORC- 05)

About the Conference The third international conference in the series of Asia-

Pacific Symposium on Radiochemistry (APSORC-05) willbe held in Beijing, China, during 2005 October 17–21. Thefirst APSORC was held in Kumamoto, Japan (1997), andthe second in Fukuoka, Japan (2001). The conference pro-vides an international forum for presentation and discussionof current and emerging sciences in all fields of radiochem-istry and nuclear chemistry, and their applications to vari-ous fields. It aims to promote academic activities innuclear, radiochemical and related sciences. Scientists,engineers and students from universities, institutes, labora-tories and industries throughout the world are encouragedto participate and make contributions.

Venue and hotel The Symposium will be held at the Grand View Garden

Hotel in Beijing. It is a four- star hotel with a beautifulview. The hotel website (http://www.gvghotel.com) is inboth English and Chinese languages. A discount price willbe provided to pre-registered participants at the rate of US$60 per person per diem for single occupancy and US$ 40

per person per diem for double occupancy in a standard room.A list of cheaper hotels will be provided upon request.

Language The conference language is English.

Organization Under the supervision of the APSORC International Com-

mittee (APSORC-IC), the Symposium is co-organized by: Chinese Nuclear & Radiochemistry Society (CNRS) China Institute of Atomic Energy (CIAE) Institute of High Energy Physics (IHEP) Peking University (PKU) Tsinghua University (THU)

APSORC-05 is sponsored by the: Chinese Academy of Sciences (CAS) National Natural Science Foundation of China(NNSFC) Chinese Chemical Society (CCS) Chinese Nuclear Society (CNS)


Calendar

Query sheetAU Q1: cut off?.

Query_A_125510.fm Page 1 Thursday, August 11, 2005 12:44 PM

calendar


2005September 10–14

Zaragoza, Spain Ninth Interna-tional Conference on Topics in Astro-particle and Underground (TAUP)

http://www.unizar.es/taup2005

September 10–15 Sant Feliu de Guixols (Costa

Brava), Spain EuroConferenceon Ultracold Gases and theirApplications.

Web: http://www.esf.org/esfgenericpage.php?section= 10&language = 0&genericpage = 2

September 12–16 Caen, France 11th International

Conference on Ion Sources ICIS05 http://www.ganil.fr/icis05

September 12–17 Kos, Greece Frontiers in Nuclear

Structure, Astrophysics, and Reac-tions Conference (FIN

http://www.inp.demokritos.gr/~finustar

September 19–24 Milos Island, Greece 6th Research

Conference on Electromagnetic Inter-actions with Nucleons an 2005)

http://www.iasa.gr/EINN 2005/

September 21–25 Kazimierz Dolny, Poland XII

Nuclear Physics Workshop Marieand Pierre Curie “Nuclear Struc-ture and Reactions”

http://kft.umcs.lublin.pl/wfj/

September 25–October 2 Albena, Bulgaria Third Sandan-

ski Coordination Meeting onNuclear Science.

Web: http://beo-db.inrne.bas.bg/albena 2005/

September 26–December 2 Seattle, Washington, USA

Nuclear Structure Near the Limitsof Stability

http://www.int.washington.edu/PROGRAMS/05–3.html

September 28–30 Santiago de Compostela, Spain

R3B-EXL Workshop http://www.usc.es/genp/Meetings/R3BEXL Sant 05/

October 3–7 Iguazu, Argentina The Sixth

Latin American Symposium onNuclear Physics and Applications

http://www.tandar.cnea.gov.ar/misc/SLAFNAP6.php

October 3–7 Zurich, Switzerland Tracking in

High Multiplicity Environments(TIME ‘05)

http://ckm.physik.unizh.ch/time05/

October 10–12 CERN, Geneva, Switzerland

Nuclear Physics & Astrophysics atCERN - NuPAC

http://cern.ch/nupac

October 12–14 Frascati, Italy Workshop on

“Nucleon Form Factors” http://www.Inf.infn.it/conference/nucleon05/

October 16–22 Dresden, Germany Workshop on

Critical Stability http://www.mpipks-dresden.mpg. de

October 17–21 Beijing, China Asia-Pacific Sym-

posium on Radiochamistry 2005APSORC-05

http://www.ihep.ac.cn/apsorc2005

October 19–21 Caen, France Workshop on

Reactions with SPIRAL 2 http://www.ganil.fr/research/developments/spiral2/

October 31–November 1 CERN, Geneva, Switzerland

ISOLDE PAC Meeting http://isolde.web.cern.ch/ISOLDE/

November 3–10 Bordeaux, France 10th Geant4

Conference http://geant4.in2p3.fr/2005/

November 18–19 Groningen, The Netherlands

NuPECC Meeting http://www.nupecc.org/misc/communications.html

November 23–25 Brussels, Belgium 3rd Interna-

tional Conference on Education andTraining in Radiological Prot

http://www.etrap.net/

November 28–29 Caen, France EURISOL Town

Meeting http://www.ganil.fr/eurisol/

November 28–December 1 Catania, Italy IWM2005-Inter-

national Workshop of Multifrag-mentation and related topic

http://www.dg-talengine.it/iwm2005/index.htm

December 12–14 GSI Darmstadt, Germany

PANDA Collaboration Meeting http://www.ep1.rub.de/~panda/auto/home.htm


calendar


December 15–20 Honululu, Hawaii, USA “SCI-

ENCE WITH RARE ISOTOPEBEAMS”, Part of PACIFICHEM2005

http://www.phy.cuhk.edu.hk/gee/pachem05/pacifichem. html

2006January 29–February 3

Bormio, Italy XLIV Interna-tional Winter Meeting on NuclearPhysics.

Web: [email protected].

March 6–10 Dresden, Germany PANDA Col-

laboration and Physics Meeting http://www.ep1.rub.de/~panda/auto/ home.htm

March 17–18 Athens, Greece NuPECC Meeting http://www.nupecc.org/misc/communications.html

March 19–23 San Servolo, Venezia, Italy

FUSION06, International Confer-ence on Reaction Mechanisms andNuclear S Coulomb Barrier

http://www.Inl.infn.it/~fusion06/

June 12–14 GSI Darmstadt, Germany

PANDA Collaboration Meeting http://www.ep1.rub.de/~panda/

auto/ home.htm

June 20–23 St. Goar, Germany 2nd Interna-

tional Conference on CollectiveMotion in Nuclei under Extreme(COMEX 2).

Web: http://www.ikp.physik.tu-darmstadt.de/comex2/

June 25–30 CERN, Geneva, Switzerland

International Symposium onNuclear Astrophysics Nuclei in theCosmos — NI.

Web: http://indico.cern.ch/conferenceDisplay.py?confld = 059

July 3–7 Cortina d’Ampezzo, Italy 7th

International Conference on Radio-active Nuclear Beams (RNB7).

Web: http://rnb7.pd.infn.it/

August 21–26 Santos, Sao Paulo, Brasil 18th

International IUPAP Conference onFew-Body Problems in Physics (FB

Web: http://www.fb18.com.br/

September 2–5 Vienna, Austria PANDA Collab-

oration Meeting http://www.ep1.rub.de/~panda/auto/ home.htm

September 2–6 Rio de Janeiro, Brasil Interna-

tional Conference on Nucleus-Nucleus Collisions NN2006

[email protected]

Q1


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