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Overview of HL-LHC Superconducting

Wire and Cable Splice Designs

C. Scheuerlein

Acknowledgements: F. Meuter, E. Tsolakis, R. Principe, D. Etiembre, L. Favier, A. Milanese, H. Prin, E. Todesco, A. Foussat, F. Rodriguez Mateos

14 April 2020

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Outline

Splice requirements and recommendations

MQXF 18 kA circuit splices1) lead cable to flat busbar (double cable)

2) flat busbar to flat busbar

3) round busbar cable to lead cable

4) round busbar cable to flat busbar cable

5) Cu cable to flat busbar cable

MCBXFB and MCBXFA 2 kA circuit splices5) Lead cable to round busbar cable

6) flat lead cable to flat lead cable

D1 and D2 13 kA circuit splices7) Lead cable to flat busbar (double cable or single cable with addiional Cu?)

8) Flat busbar cable to round busbar

MQXF CLIQ lead splices

200 A wire splice

MBH 11 T dipole trim wire to main bus splices

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Splice requirements Splice mechanical integrity and robustness (define number of thermal and

powering cycles for fatigue testing, where needed)

Additional Cu stabilizer continuity

Splice resistance Huge margin of acceptable heating power when operating Nb-Ti/Cu splices in

liquid He.

The splice resistance and its reproducibility is a useful indicator of the reliability of the splice manufacturing processes.

Splice resistance specification [1] E. Todesco, L. Bottura, H. Prin, Y. Leclerc., S. Feher, “BUSBARS FOR WP3 CONNECTED TO DFX”,

Maximum current imbalance in the conductor introduced by resistance variations of the individual wire or cable resistances

Splice insulation dielectric requirements

Splice, insulation and tooling dimensions

Possibility to disconnect and reconnect the splices in the LHC tunnel with standard tools

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Parameter (units) Triplet D1 MCBXFA/B

Design current (kA) 18.0 13.0 1.73

Operating temperature (K) 1.9 1.9 1.9

Joint resistance (per joint) (nΩ) 1 1 3

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Splice design recommendations

Robust splice design

As similar as possible to proven LHC splice designs

Easy and reproducible splice manufacturing processes (all

WP3 splices are soft soldered lap splices)

Possibility of in situ non destructive testing

Have big critical current conductor margin

Ideally Cu cross section in the conductor is sufficient, and

no additional stabiliser splices are required

To have good current sharing between all wires

Equal resistance between all cables of a splice

Splice overlap length equals the cable transposition pitch length, or

multiples of it

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Magnet coil conductors

https://espace.cern.ch/HiLumi/WP3/SitePages/Home.aspx

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MQXF 18 kA lead cable and busbars

MQXF lead cable produced by MSC-

SCD

18.15 mm width and 1.92 mm height (not

keystoned)

Transposition pitch=120 mm is made of 34

pre-tinned Nb-Ti wires LHC type 01

(=1.065 mm, Cu/Sc ratio=1.65, RRR>150,

Ic (10T,1.9 K)>515 A)

18 kA flat busbar is made of two MQXF

Nb-Ti lead cables soldered together

(busbar 18.15 mm × 3.84 mm)

Is the 18 kA Cu cable already defined?

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18 kA round busbar cable

18 kA round cable produced by MSC-SCD.

35 LHC type 01 wires around a 11 mm

diameter multi-filamentary Cu core

Transposition pitch?, Ic?, Cu cross section ?

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18 kA circuit splices

18 kA splice types:

1) lead cable to flat busbar (double cable)

2) flat busbar to flat busbar

3) round busbar cable to lead cable

4) round busbar cable to flat busbar cable

5) Cu cable to flat busbar cable

5 splice types, assuming no “triple” splice

Maximum length of a lead cable without additional stabiliser?

How are the diodes connected to the Cu cable ?

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Figure 1 — Conceptual design of the busbar segments in the 18 kA circuit [1] E. Todesco, L.

Bottura, H. Prin, Y. Leclerc., S. Feher, “BUSBARS FOR WP3 CONNECTED TO DFX”,

<< << <<

Q1a Q1b Q2a Q2b Q3a Q3b CP D1

DFXLine N1

magnet leads flat busbar round busbar

DCM

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Flat busbar to flat busbar splice

Three different lap splice configurations possible

FNAL soldered both busbars directly, resistances of four splices

ranged from 0.14 nΩ to 0.42 nΩ

Resistance of splice and current homogeneity can be improved

when cables are interleaved.

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From M. Baldini et al, IEEE

Trans Appl. Supercond. 30(4),

2020, Art No. 4003305

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Flat busbar splice resistance

Measured MQXF lead cable splice, 120 mm overlap resistance: R=0.34 n (calculated from =888±102 s (assuming

a loop inductance of 306 nH).

Expected resistance for an interleaved splice is R=0.17 n One additional cable between loop

cables: R=0.60 n (=513 s, 306 nH).

Two additional cables between loop cables: R=0.89 n (=342 s, 306 nH).

Three additional cables between loop cables: R=1.21 n (= 252 s, 306 nH).

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MQXF Nb-Ti lead cable splice resistance vs number of cables through which the current has to pass

y = 0.3026xR² = 0.9952

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1 2 3 4 5

Splic

e re

sist

ance

(nΩ)

Number of cables between filaments

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MQXF Nb-Ti Rutherford lead cable to round

18 kA trim cable splice design

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Photograph of 18 kA trim cable to Rutherford cable splice prototype.

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MCBXFB and MCBXFA circuit conductors

2 kA Nb-Ti lead cable, Rutherford cable made of 34 wires Ø=0.48

mm, 4.37 mm-wide, 0.845 mm-mid-thickness, transposition pitch 33

mm

Round cable is extracted from LHC conductor (made of three round 6

kA cables).

Each 6 kA cable is made of 13 Nb-Ti wires (Ø=0.85 mm) and 7 Cu

wires in the core.

Flat 2 kA bus? Is it a double lead cable?

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µ-CT cross section of LHC 6 kA cable. EDMS No. 2215669

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2 kA circuit MCBXFB and MCBXFA splices

6) round busbar cable to

flat magnet lead cable

7) round busbar cable to

flat busbar cable

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13 kA conductors

13 kA lead cable is LHC type 2 Rutherford cable (36 wires 0.825 mm,

15.1 mm 1.48 mm mid-thickness, keystoned, transposition pitch 100

mm)

13 kA flat busbar is soldered together with a keystoned Cu stabiliser.

Is there a round 13 kA cable, or will the round 18 kA cable be used?

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13 kA D1 circuit splices

8) Rutherford lead cable to flat busbar

9) Flat busbar cable to round busbar

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<< << <<

Q1a Q1b Q2a Q2b Q3a Q3b

DFXLine N1

magnet leads flat busbar round busbar

<< << <<

Q1a Q1b Q2a Q2b Q3a Q3b D1

Line N1

magnet leads flat busbar round busbar

CP

DCM

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600 A wire splice resistance (correctors)

Nb-Ti/Cu wire

Ø1.6mm, (Nb-

Ti/Cu ratio=0.1)

3.86±0.72 nΩ

(crimp and solder)

2.52±0.19 nΩ (with

Cu profiles

soldered)

3.00.2 nΩ (US

welded)

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Splice voltage taps

Should splice voltage tap connections be included in the splice

summary?

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MBH 11 T dipole trim line main busbar splices

Trim cables made of 4 Nb-Ti/Cu wires Ø1.6mm, (Nb-Ti/Cu

ratio=0.1) see specification EDMS No. 366575.

Wires are soldered to the main busbars at a groove in the main

splice Cu profile

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MBH 11 T dipole internal splices

Add internal magnet splices in overview?

11 T dipole internal splices in LHC-LMBH-FP-0019, EDMS No.

1989368

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Questions concerning the conductor

Is the 18 Cu conductor to the diode module already defined?

Are the splices to the diodes already defined, are there bolted pressure splices?

Is it foreseen to have a 13 kA round cable, is there already a design of this cable, or will the 18 kA round cable also be used in the 13 kA circuit?

Is the flat 13 kA bus a LHC double cable, or a single cable with additional Cu stabiliser?

Is the flat 2 kA busbar a double cable?

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Next

Functional splice specification

Get all info on the layout of conductors that have to be

interconnected

Get all info on already existing splice development work

Develop splice designs

Develop interconnection tools

Produce laboratory splices and perform validation tests.

Develop NDT tests

Develop and validate splice insulation systems

Develop splice production procedures and test them in

situ in mock- ups

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References

E. Todesco, L. Bottura, H. Prin, Y. Leclerc., S. Feher, “BUSBARS FOR WP3 CONNECTED TO DFX”,

E. Todesco et al, Busbars for Q1 to D1 magnets”, https://indico.cern.ch/event/830202/contributions/3476759/attachments/1867092/3070601/et_busbar_2019-06-21.pdf

M. Baldini et al, “Characterization of NbTi busbar for HL LHC Interaction Region Quadrupoles”, IEEE Trans Appl. Supercond. 30(4), 2020, Art No. 4003305

Nb3Sn-Nb-Ti splice tests https://edms.cern.ch/ui/#!master/navigator/document?D:1814373709:1814373709:subDocs

H. Prin, “How are the splices made between the trim bus bars (11T MBH), the k-mod and the CLIQ feeders (QXF), as well as the trim bus bars to the magnet leads (QXF) at the level of the cold mass?”, https://indico.cern.ch/event/835702/contributions/3560659/attachments/1905099/3146122/2019-09-10_Int._Circuit_review_closed_session_HP.pdf

H. Prin, “Busbars integration in the cold masses” https://indico.cern.ch/event/477759/contributions/1156018/attachments/1246170/1835566/2016-03_Busbars_routing_inside_the_cold_masses.pdf

R. Bossert, “Status of bus and interconnect“, at 8th HL-LHC collaboration meeting, (2018), https://indico.cern.ch/event/742082/contributions/3141508/attachments/1734744/2805370/Bus_and_Int_-_Hi-Lumi_oct_2018.pdf

R. Herzog, LHC-DCA-CI-0002, EDMS No. 366575 , “Technical Specification for the manufacture of the superconducting 600 A multi-conductor cables for the LHC”, (2002) https://edms.cern.ch/ui/file/366575/1/IT3140TechSpec.pdf

J. Fleiter, https://indico.cern.ch/event/689576/contributions/2831218/attachments/1582569/2501211/Cable_design_approach_and_experience_at_CERN_J._Fleiter_V2.pdf

S. Heck, FEM investigation of the influence of electrical properties and geometric shape on the resistance of soldered cable-around-conduit conductor joints , EDMS Nr:1150055

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