Quench Performance of the HTS Insert Solenoid With REBCO CORC Cable at 4.2 K 18.5 T Background Magnetic Field

The maximum magnetic field designed for the Central Solenoid (CS) of the China Fusion Engineering Test Reactor (CFETR) is more than 17 T. Because the Rare-earth Barium Copper Oxide (REBCO) coated conductor has high current carrying capability under a high magnetic field, it may be used on the CS coil. In the practical application of the REBCO, quench detection is important for magnet safe operation. In this paper, a 4-turn solenoid magnet has been wound from 3 meters of conductor on round core (CORC) cable, which was tested at 77 K, self-field, and 4.2 K, 18.5 T. The aim is to explore the quench characteristics of the REBCO CORC cable under a high magnetic field and prepare for the HTS quench detection system of CFETR. In the 77 K, self-field experiment, there was no significant temperature rise and the quench voltage was below 1 mV/m within 20 s. In the 4.2 K, 18.5 T experiment, the voltage developed slightly slower at the start of the quench, but a strong thermal effect then was generated and the voltage began to change dramatically. From these experiments, we have concluded that setting the voltage threshold to 1 mV/m and the delay time within 200 ms is a suitable choice when the CORC cable we designed operates at 4.2 K with the background magnetic field below 18.5 T. These experiments provide a valuable reference for determining the HTS quench detection threshold in CFETR.