ReBCO CORC Cable-In-Conduit Conductors for Large-Scale Magnets and Bus Lines

1. ReBCO CORC Cable-In-Conduit Conductors for Large-Scale Magnets and Bus Lines Tim Mulder1,2, Danko van der Laan3, Jeremy Weiss3, Alexey Dudarev1 and Herman H.J. ten Kate1 1 CERN, Geneva, Switzerland2 University of Twente, Enschede, the Netherlands3 Advanced Conductor Technologies, Boulder, Co, USA CCA 2018, Vienna, Austria, 11-9-2018

2. CORC Wires, Cables and CICCs Ø 2-4 mm CORC Wire (Picture courtesy ACT) CORC Cable/Strand CORC Cable-In-Conduit Conductor Ø 5-8 mm CORCWire: accelerator magnets, high-field insert coils or standalone solenoids. CORCCable:general purpose, stable SC magnets and power transmission. CORCCable-In-Conduit Conductor (CICC):high current, high-field magnets and HTS bus bars. • Advantages of CORC: • Isotropic Bending • Flexibility • Internal Core Stabilized

3. CORC CICC Bus Bars for Large Magnets Cryogenic plant and the power convertor on surface. Bus bars based on the CORC CICC conductor are lighter and take less space. Several detector magnets with stored energy from 14 to 70 GJ and with currents between 30 and 80 kA are under investigation. 400 m Flexible bus bars prevent disassembly and assembly of these bus bars during maintenance. Detector Cavern

4. First-in-the-World CORC CICC • First ReBCO CORC Cable-In-Conduit-Conductor (2016) • Six-Around-One Layout • Aluminum 5083 alloy jacket • Liquid Bath Cooling (LN2 & LHe) • Testing of Production Techniques • 48 kA @ 4K/10T and 13 kA @ 77K/Self-Field 2016

5. Two New CORC Cable-In-Conduit Conductors Cu-Jacket Copper Steel Voids Grooves for cooling tubes ReBCO tapes Fusion type of magnets • Can sustains high stress • Can cope with large heat loads SS-Jacket 35 mm 35 mm Both CICCs are 2.8 m long and rated for 80 kA at 12 T and 5 K. 40 mm 40 mm Locking mechanism Detector magnets and Bus Bars • High thermal & electrical stability • Practical cooling

6. CORC Strands for the CICCs

7. Test Results: Full Conductor SS-jacketed CICC for Fusion Magnets: Performed according to prediction at 40 to 60 K N-value of 14±3 (similar to the 2016 sample) Cu-jacketed CICC for Detector Magnets & Bus Bars: Only 30 – 40 % of predicted Ic Low n-value of 5±2 in the 40 to 60 K range Degradation occured onlywith Cu-jacketed CICC. Both conduction and forced-flow convection cooling proved valid for such conductor.

8. Test Results: Single Strands and Tapes Sections Tapes Strands Single strands were extracted from Cu-jacketed CICC and tested at 76 K in self-field at ACT: Major degradation in high-field region of Cu-jacketed CICC. Single tape show mainly damaged inner tapes. CCA 2018, Vienna, Austria – 11-09-2018

9. Test Results: Cause of Stand Degradation ReBCO tapes • Likely cause of the degradation: • Primary failure mode is a pinching effect. • Specific for CORC strand layout/winding parameters of the Cu-jacketed CICC. • Next steps: • New CORC CICC is in preparation to replace the degraded Cu-jacketed CICC. • New strand layout is used with a thicker core. • Smaller tolerance between 6-a-1 cable and jacket. • Test scheduled for early 2019 in SULTAN. Copper tapes CCA 2018, Vienna, Austria – 11-09-2018

10. Conclusion • Two new 2.8 m long high-current CORC CICCs were prepared and tested • Icfor the CORC CICC for Fusion is according to prediction • Icfor the CORC CICC for Detectors is 30 to 40 % of the predicted value • Main cause of the degradation is found to be a pinching effect on the CORC strands • Results achieved, clearly demonstrate that exercising conductor production is extremely useful in order to identify relevant design and production parameters for controlling the quality of these new-technology conductors. • Next: New Cu-jacketed CICC test in SULTAN