C. J. Kovacs, M. Majoros, M. D. Sumption, E. Collings 2MOr1A-03 - Coated Conductors II: Properties Important for Applications REBCO Roebel cable stability, current sharing, and quench measurements in a liquid helium bath and applied magnetic fields up to 10 Tesla C. J. Kovacs, M. Majoros, M. D. Sumption, E. Collings This work was supported by the U.S. Department of Energy, Office of Science, Division of High Energy Physics, under Grant DE-SC0011721

2MOr1A-03 - Coated Conductors II: Properties Important for Applications Motivation Measure: MQE NZP Current Sharing All at varying I/Ic of REBCO Roebel cables in LHe at fields up to 12 Tesla. Previous measurements by Majoros et al. at 77K demonstrated high ICR and little current sharing without the use of soldered on copper splices. Majoros et al. “Stability, Inter-Strand Contact Resistance, and AC Losses in YBCO Roebel Cables” IEEE Trans on Appl Supercond 24, 3 (2014)

Probe G-10 U-shaped holder Helium cooled leads (rated for 1000A) 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Probe G-10 U-shaped holder Helium cooled leads (rated for 1000A) Teflon sheet and Kapton Tape to hold sample stationary. Designed to barely fit in 60mm bore magnet.

2MOr1A-03 - Coated Conductors II: Properties Important for Applications Probe

Sample 9-tape REBCO Roebel cable. 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Sample 9-tape REBCO Roebel cable. Tapes from SuperPower, Cable from Robinson Research Institute. Each 14mm tape ~300A at 77K (before cut). Width off individual tapes after cut: 4.9 mm Length of cable inbetween solder regions: 35.5 cm Shielded from direct LHe environment with kapton/Teflon sheet wrap.

Instrumentation 40 voltage taps 5 Type-E thermocouples 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Instrumentation 40 voltage taps 5 Type-E thermocouples 3 40Ω Kapton heaters Labview with: National Instruments DAQ Lakeshore 224 Temperature monitors Keithley 2182A nanovoltmeters = Voltage Tap = Type-E Thermocouple = Kapton Heater = Soldered Current Tap

Ic Measurement at 10T and 4.2K 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Ic Measurement at 10T and 4.2K Iq= 1140 amps Quench protection worked and sample not damaged. No current sharing was witnessed. There was an baseline during current ramping (1A/s), most likely a thermovoltage. Voltage jumps are likely due to cable transverse motion due to Lorentz forces The cable wasn’t epoxy impregnated and at 10T and carrying 1140 A the transverse force on the cable was 140 lbs.

Heat Pulse Measurement 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Heat Pulse Measurement

Heat Pulse Measurement 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Heat Pulse Measurement I/Ic= 0.27 (300A) Heat pulse was 37 J total (~3.7W over 10s) No transverse current sharing was witnessed, so: MQE > 37 J at 10T, 4.2K, and I/Ic=0.27

Instrumentation Damage 2MOr1A-03 - Coated Conductors II: Properties Important for Applications Instrumentation Damage After the Ic measurement (which was above the recommended 1000A current lead limit) instrumentation wires were damaged due to heat. An additional feedthrough was leaking helium gas pressure, preventing it from traveling through the He-cooled leads.

2MOr1A-03 - Coated Conductors II: Properties Important for Applications Conclusions The Ic at 10T and 4.2K of the 9 tape Superpower REBCO Roebel cable was 1140A. The MQE of the cable with I/Ic=0.27 and at 10T and 4.2K was greater than 37 J (assuming 100% of the energy went into the cable).