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W.Goldacker

Latest developments and challenges in developing Coated Conductor magnets for accelerators within EUCARD2 Wilfried Goldacker1, Anna Kario1, Simon Otten1, Glyn Kirby7, Hugues Bajas2, Jeroen van Nugteren7, Amalia Ballarino2, Marta Bajko2, Luca Bottura2, Gijs de Rijk7, Lucio Rossi2, Maria Durante3, Philippe Fazilleau3, Clément Lorin3, Antti Stenvall4, Alexander Usoskin6, Jerome Fleiter2, Jaakko S. Murtomäki2, Peng Gao8, Sander Wessel8, Marc M. J. Dhalle8, 1.KIT, Karlsruhe , Germany; 2. CERN, Geneva, Switzerland; 3. CEA, Paris, France; 4.TUT, Tampere, Finland; 6. Bruker, Alzenau, Germany. 7.TE/MSC/MDT, CERN, Geneva, Switzerland; 8.Univ Twente, Netherlands

Wilfried Goldacker EUCAS - Lyon (F) - Sept. 7th-10th. 2015 Wilfried Goldacker CCA – Aspen - Sept. 12th-14th. 2016

CCA ASPEN CO-USA 2016

Wilfried Goldacker Coated Conductors for Application, Aspen CO-USA - Sept. 11th-14th. 2016

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1.  Develop a 10 kA-class cable in HTS (High Temperature Superconductor) suitable for accelerator (collider) magnets

»  Large current to reduce magnet protection issues, »  Develope cable properties suitable for accelerators (AC losses, coupling/persistent currents, mechanical behavior…) »  Uniformity of properties over long lengths

2.  Design, Manufacture and test a first accelerator, small prototype quality dipole which is applying HTS Roebel cables

»  Bore diameter 40 mm »  Outside diameter, 99 mm to be inserted in Fresca2 facility »  Length > 400 mm »  Field 5 T stand-alone good geometric homogeneity ( ∼10-4)

»  Field > 15 T in a HF magnet (Fresca2) – Outside EuCARD2

Main scopes of Eucard2 WP10, Future Magnets

Decision made on HTS-Roebel-cables from CC


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Addressed topics in the talk

• Overview of magnet design approaches

• Choice of Coated Conductors

• Status of Roebel preparation technology

• Transverse stresses of impregnated cables

• Bending ability of CC‘s and cables

• Cables in windings of aligned block design (CERN)

• investigation/qualification of quench detection methods

• Cold test for aligned block design

• Alternative approach of „cosine-theta“ design (CEA)

• Conclusions and outlook

Wilfried Goldacker CCA – Aspen - Sept. 12th-14th. 2016 Wilfried Goldacker Coated Conductors for Application, Aspen CO-USA - Sept. 11th-14th. 2016

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Parameter units target minimum

JE (20 T, 4.2 K) (A/mm2) ≥ 600 ≥ 400

s(Ic) (%) ≤ 10

m0DM (1 T, 4.2 K) (mT) ≤ 300

Allowable stransverse (MPa) ≥ 150

Allowable elongitudinal (%) ≥ ±0.3

Unit Length (km) ≥ 100 ≥ 30

Design was adopted to Roebel cable properties •  Bending ability like single CC •  Cable parameters flexible •  High filling factor > 90% ! •  Full transposition •  High current due to current

anisotropy in field

Magnet approach 1: Aligned Block Design CERN The goal: 5 T (stand-alone) dipole magnet for 4.2 K, 40 mm aperture 10 kA operation current at B = 17 - 20 T as insert made from REBCO coated conductor Roebel cable

The dipole insert magnet design of CERN „Aligned block design“

Wilfried Goldacker CCA – Aspen - Sept. 12th-14th. 2016 Wilfried Goldacker Coated Conductors for Application, Aspen CO-USA - Sept. 11th-14th. 2016

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9.89 mm

Courtesy Maria Durante Give cable space! Winding experiment with KIT Roebel Dummy (Stainless Steel) + Insulation

•  Test of 3D bending ability •  Handling of the winding process •  Assess a cable design suitable to provide

enough space for re-arranging the strands

Horizontal gap

Vertical gap Options for change in Roebel design

Wilfried Goldacker EMA - Orlando (FD) USA - Jan. 28th. 2016

Magnet type 2: Cosine-Theta approach CEA


Requires complex bending of cable !

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360° twist

180° twist

•  2D magnet ends cross-‐sec0on at twist part

6

Racetrack coil (above beam tube) 180° twist one side 0° on the other

Flared-‐ends coil (below beam tube) 180° twist one side 360° twist on the other

Flared-‐ends coil

Straight part

90º twist ew + 90º twist Winding head

From Lucio Rossi@ EuCARD² 3rd annual meeMng -‐ 27/04/2016

Magnet type 3: Stacked tape design, CNRS Grenoble

Comment: winding procedure is very complex including a transposition


Transposition along one side, Ic anisotropy averaged out

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Highest layer JC obtained in an industrial process

Master plot (C. Senatore, U. Geneva)

Investigation of industrial CC materials •  Investigation of Bruker, SuperOx, SuNAM, THEVA, SuperPower, Fujikura •  Criteria: Current capacity at 4.2 K, punching ability for Roebel strands,

current homogeneity, delamination sensitivity, customized improvement !

•  Bruker qualifies as material with best 4.2 K in field performance

•  Reason is a complex combination of different types of flux pinning sites

•  Substrate thickness of 100 microns is actually a hint for Jc

eng and bending


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Preparation issues for Roebel cables Test of different coated conductors for Roebel approach And a couple of hints and problems

Key process: Strand punching !

•  Dimension accuracy of CC (width,

straightness, dog boning from Cu)

•  Delamination sensitivity !!

•  Material composition and thickness

•  High precision requires material

specific punching tool (gap tolerance)

•  Switch from flexible approach

(punching of segments, free choice of

transposition length) to fixed geometry

with lp= 300 mm (new tool)


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20 µm

•  The average critical current per unit width degraded only 6% after punching and copper plating.

•  No local defects were found.

Delamination can be avoided, however some effects on geometry:

Stainless Steel

Cu Ag

punching burr

•  width of this Cu plated tape is 5.46-5.67 mm and thickness 176 - 207 µm

0

2

4

6

8

10

12

1-‐10 1-‐2 2-‐3 3-‐4 4-‐5 5-‐6 6-‐7 7-‐8 8-‐9 9-‐10

A/mm

Cri0cal current per unit width

Before punching

AZer punching

AZer copper plaMng

Thickness measurements at different points:

Stabilisation of Roebel strands successful with Punch & Coat strategy (Cu plating on CC+Ag)

In summary P&C is applied for Bruker tape and was also demonstrated with SuperOx CC Now mandatory for the Eucard Roebel cables ! A future Roebel standard ?!


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•  SuNAM

•  TL: 300 mm, 5.85 mm strand width

•  15 strands, 5.94 m long

•  17 µm tool, REBCO

•  SuperOx

•  TL: 300 mm, 5.85 mm strand width

•  15 strands, 6.15 m long

•  7 µm tool, REBCO down

Roebel cable test lengths, about 6 m for Feather M-0


Bruker 2 cable geometries:

• « skinny » 15 tapes of 0,1 mm thickn. # 1 mm

• « fat » 13 tapes of 0,14 mm thickn. # 1,1 mm

From 226 mm to 300 mm transposi0on to address the issues detected by dummy cables

15 BHTS tapes (0.14 mm), 5 m Expected IC (4.2 K, 20 T) ≈ 4.2 kA

SS dummy

W.Goldacker Wilfried Goldacker Coated Conductors for Application, Aspen CO-USA - Sept. 11th-14th. 2016

Transverse Stress in Roebel cables

•  Roebel cable surface topology requires flatening by impregnation to distribute the transverse stress charge

•  Void free impregnation the challenge

•  Delamination of CC not acceptable, gap fills up with resin

Areas of transverse stress on cable surface, measured by pressure sensitive foil (left), calculated (right)

Impregnated cable G.Kirby , J. Nugteren CERN

Careful void free impregnation is

mandatory !

J. Fleiter et al. SUST 26 (2013) 065014

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NbTi pancake coils

11 T solenoid

Pressure anvil

Sample holder

Cable sample

F

"   T = 4.2 K "   Imax = 50 kA " Bmax = 11 T (perpendicular) " Fmax = 250 kN "   U-shaped samples

Twente transverse stress rig

12 mm

Transverse stress on impregnated Roebel cable

Wilfried Goldacker EMA - Orlando (FD) USA - Jan. 28th. 2016

KIT method Al2O3 filled resins have best match of thermal expansion to CC‘s


S Otten et al. SUST 2015 Volume 28, Number 6

Sample impregnated in U-shape form

Resin filled Roebel gap

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Successful impregnation methods KIT and CERN Peng Gao et al. Twente Univ. ASC-2016 Denver 2LPo2D-06


W.Goldacker Wilfried Goldacker Coated Conductors for Application, Aspen CO-USA - Sept. 11th-14th. 2016

Transverse stress for advanced impregnations Peng Gao et al. Twente Univ. ASC-2016 Denver 2LPo2D-06

•  Both methods work well

•  Tolerable 450 MPa transverse stress measured

•  The results meet the expected transverse stress hot spots (comes later !)

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Bending investigations on HTS CC & Roebel cables S.Otten et al. ASC-2016 Denver 2LPo2D-09 .

•  No pre-strain load from cabling for Roebel approach !

•  All strands have equal boundary conditions for sample lengths multiples of the transposition pitch

•  Bending behaviour is then uniform to the strands

Voltage taps

Bent section

Current contacts

Contineous bending strain rig (CBSR) for cables (77 K)

Contineous bending strain rig (CBSR) for CC (77 K)

R R-d/2 R+d/2

2 orientations (HTS inside, outside) measured simultaneously


W.Goldacker Wilfried Goldacker CCA – Aspen - Sept. 12th-14th. 2016

Bending results for different coated conductors

Main difference in the reversible bending behaviour observed

ASC-2016 Denver


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Bending results for 2 Roebel cables (SP, Bruker CC) S.Otten et al. ASC-2016 Denver 2LPo2D-09, (acc. for publ. SUST)

•  Main difference is the substrate thickness •  Cables behave very similar as the single tapes •  No irreversible strains observed for smallest

bending radius •  Comment: Measurements at 77K improve

slightly results (higher prestrain as at RT)

•  Samples are dense packed •  Influence of the copper plating quality

on cross section, Jc and impregnation quality (dog boning)


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Dipole magnet design: baseline lay-‐out

18

Aligned block design


Structure and coil design using so named “fat” cable

Structure and coil design using so named “skinny” cable


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Feather M-‐0 prototype coils


•  Several Feather 0 prototype coils manufactured (dummy and real Roebel cables from KIT up to 20 m)

•  Development of winding and impregna0on, Tooling

•  Tests to assess quench detec0on principles and methods in Roebel cables

•  A range of new detec0on system are being tested (pickup coils, temperature sensors, acous0c sensors)


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Investigation of stability & quench chracteristics Feather M-0 G.A.Kirby et al. ASC 2016 (1LOr1B-01), paper submitted to IEEE

•  The problem is to have a measurable signal in a sufficient short time

•  This is the case after current redistribution (whole cable length !) and final full quench

•  Reaction time depends crucially on operation current


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Pick - up coil array for quench detection G.A.Kirby et al. ASC 2016 (1LOr1B-01, paper submitted to IEEE

•  Current redistribution leads to change of flux position •  Change of flux is detected by pick-up coils

•  pick-up coil structure printed on both side of Kapton foil

•  Coil dimension correlated with Roebel transposition length for enhanced signal

•  Detection of whole winding length required, since quench and current redistribution appears within whole length


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22

Printed Pick-up coils 285 turns per coil


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Modelling stress situation in Feather M-2 Jaakko S. Murtomäki et al: ASC 2016, 3LPo2F-03

23 253 MPa


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Modelling of stress situation in Feather M-2 G.A.Kirby et al. ASC 2016 (1LOr1B-01, paper submitted to IEEE

•  Coil shows hot-spots for stress at cable edge •  Cable can balance transverse stresses up to 450 MPa

impregnated with „CERN-resin“


J. Murtomäki et al. ASC 2016, 3LPo2F-03

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First cold test of subsize Feather M-0.4 coil G.A.Kirby et al. ASC 2016 (1LOr1B-01, paper submitted to IEEE

•  Tests on Feather M0-x coils serve to advance production and experimental features

•  Recent tests ran during ASC with success:

•  Feather M-0.4 performance 100% of prediction from CC performance !!! e-mail Kirby 11th Sept


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Feather 2 parts are ready One highlight: additive 3D manufacturing of 316 L SS body

26


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Two coil designs based on fat (A) and skinny (B) cables

Cos-θ A : 1.2 mm + 2x100µm insulation, 14 turns Cos-θ B : 1.0 mm + 2x125µm insulation, 17 turns

Layout Unit Cosϑ A Cosϑ B

Iop kA 11.68 10.06

Bop T 5 5

Bpeak T 5.7 5.8

Ic kA 14.4 15.2

LL margin (%) 20 34

T margin K 20 30

Layout Unit Cosϑ A Cosϑ B

Sd. inductance mH/m 0.49 0.73

coil inner radius mm 22 24

yoke inner raidus mm 50 50

yoke outer raidus mm 112 110

Nb. of turns - 14 17

Unit len. of cond. m 20 24

Cosine-Theta approach CEA for 2 cable types

Verification of winding with insulated Roebel dummy is done


M. Durante et al. ASC-2016, 4LPo1D-04

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Mechanical test of the cos-theta coil end geometry (CEA Saclay + KIT):

•  Shown with dummy

•  Test at KIT with HTS

(77 K, s.f.)

•  CERN-3D form prints

Courtesy of M. Durante


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•  No degradation observed

•  Small Ic increase (reversible in cable 2)

1425

1430

1435

1440

1445

1450

1455

1460

1465

1470

1475

Cable 1 (leZ-‐hand wound) Cable 2 (right-‐hand wound)

Cri0cal current [A

]

Roebel cables in CEA torsion mold (T = 77 K, self-field)

straight

mold no. 3

mold no. 2

mold no. 1

mold removed

Twist pitch [mm]

Bending radius [mm]

Mold 3 535 -

Mold 2 389 -

Mold 1 389 22

•  no degradation of Ic with all used molds •  All design specific bending works well

Cable test of the cos-theta coil end geometry


Magnet winding was tested successfully with insulated Roebel SS dummy

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Summary

•  A reliable Roebel cable performance can be provided by advanced preparation and punch & coat technology

•  Solution for magnet quench detection/protection approved •  Aligned Block design as first choice confirmed (much lower

losses as Cosine-Theta approach) •  First cold tests of subsize coil Feather M-0.4 with 100 % success

Outlook • Final dipole magnet Feather M-2 on track in time !

• Need in future of advanced CC performance & cable processing

• Automatic fabrication process of „dense Roebel cable“ ?

• KIT DOCO-Roebel-cable proposed for future full size magnets


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