1. HTS Roebel cables for the EuCARD2 “Future Magnets”
A. Kario, S. Otten, A. Kling, W. Goldacker (KIT)
C. Senatore, C. Barth, M. Bonura (UG)
L. Bottura, G. Kirby, J. van Nugteren (CERN)
Y. Yang (US)
M. Dhallé, B. van Nugteren (UT)
Rutt, A. Usoskin (Bruker)
C. Lorin, M. Durante (CEA Saclay)

2. HTS magnet insert development (WP10):
Conductor
Cable
Coil
CEA Saclay - Cos-theta design
C. Lorin et al.
B(T)
CERN- block coil design
J. van Nugteren et al. Wl Wc Tp

3. Coated conductors performance at 4.2 K:
Target performance for RE123 tape at 4.2 K in perpendicular magnetic field:
Jeng = 450 A/mm2 at 15 T
Jeng = 400 A/mm2 – 600 A/mm2 at 20 T

4. Punching technology - fast reel-to-reel:
Roll feeder
Front punch
Back punch
Reel-to-reel system
60 kN pneumatic press
Coated conductor tape
Punched Roebel strand
Roebel cable
2 movable punches and dies
Advantage: flexibility in punching geometry
Disadvantage: Multiple steps per transposition needed

5. Long length tapes for Roebel cable have been delivered:
Highest JE
12 mm wide Bruker tape
m long pieces
Homogeneous Ic (+/-10%) along the length
20 micrometre (per side) Cu stabilisation
±10 %

6. EuCARD2 first Bruker Roebel cable – 5 m long:
15 strands cable
226 mm transposition length
5.5 mm strand width

7. Cross-section of the first Bruker Roebel cable:
Roebel Ic design (sum of all strands at 77 K, s. f.) A
Roebel Ic predicted (with s.f., 77 K) – 749 A (13 % s. f. reduction)
Roebel Ic predicted (with s.f., 77 K) – 603 A (30% s. f. reduction)

8. Cu-plated tape after punching – at Bruker:
20 µm
Stainless Steel Cu Ag
punching burr
A. Jung (KIT)
Tape thickness after copper plating.
181 µm
207 µm
185 µm
176 µm
188 µm
202 µm
The average critical current per unit width degraded by 6% after punching and copper plating.
No local defects were found.

9. First 2 m long Roebel cable made with punch and coat technique:
Roebel cable: 226 TL, 15 strands
Punch + Coat
Assembled
2 m long
283 D tape

10. AC losses of the Roebel cable:
Quantitative validation numerical EM model
Perpendicular field behavior dominated by strand hysteresis
Signatures of coupling in parallel field
4.2 K measurements on 15-strand Roebel CERN (SuperPower material, impregnated)

11. Transposition lenght (Tp)
New design of the Roebel cable:
Cable design lead to problems in coil winding:
Strand „pop-up“
Similar effect in cos-θ coil at CEA Saclay (picture by M. Durante) Wl Wc Tp
Transposition lenght (Tp)
(mm)
Strand width (Wl)/
Bridge width (Wc)
226 (old)
5.5
300 (new)
5.85
Horizontal gap
Vertical gap

12. New punching tool and cable geometry:
New geometry now possible in punching tool
5.85 mm strand width
300 mm transposition length
Baseline for next EuCARD2 cables
174 µm
240 µm
Cross-section of first punched cable with new geometry (15 strands).
10.2 µm

13. Mechanical test of the cos-theta coil end geometry:
Measurement at KIT with
CEA Saclay (77 K, s.f.)
CERN and CEA -3D form print

14. No degradation of Ic with all used molds:
Twist pitch [mm]
Bending radius [mm]
Mold 3
535 -
Mold 2
389
Mold 1 22
No degradation observed
Small Ic increase (reversible in cable 2)

15. Irreversibility point
Roebel cable bending – cable suitability for a coil:
Aligned block coil
Cos-theta
coil
Irreversibility point
Bending radius [mm]
Reduced critical current
Measurements at LN2, s.f.
REBCO inside / compressive bending
Ic of the Roebel cables:
SuperPower: 1427 A
Bruker: 658 A
SuperPower
20 µm Cu, 50 µm Hastelloy
Bruker
20 µm Cu+, 100 µm SS

16. HTS Roebel cables for the EuCARD2 “Future Magnets”
Conductor
Cable
Coil
Coated Conductor:
Tapes for different supplies being tested (tape Je, punching).
Successful Bruker technology - punch and coat approach.
Roebel coated conductor cable:
First 5 m long cables were made and delivered for coil winding.
Punch and coat technology used for first 2 m long cable.
Cable design change towards magnet design.
Roebel cable for the coil winding:
First results on AC losses of impregnated cable.
It is possible to wind the cables into small radius coils without Ic degradation and test those at 77 K.
Cos-theta end design tested-no Ic cable degradation.