Preliminary Study on 2 × 2 Parallel REBCO Stacks for 8 kA Current Leads

The integration of high-temperature superconducting (HTS) technology into fusion magnets necessitates advanced cabling solutions. This study presents the design and fabrication of a prototype Stacks-in-Conduit-Conductor (SICC) cable for a current lead. The current lead comprises a 2 × 2 parallel REBCO stacks, each consisting of 30 layered REBCO tapes. Three repeated experiments were conducted in a liquid nitrogen environment, applying a current of 8 kA. Voltage measurements revealed a negative voltage profile in the inter-stack voltages indicating effective current sharing among the REBCO stacks. Similar inter-stack voltage profiles were confirmed through simple circuit analysis. The loss across the REBCO stacks, including contact resistance, was measured to be less than 1 W. However, when a copper block was incorporated, the total loss of the current lead increased to approximately 5.6 W. Further improvements can be achieved by optimizing low-resistance termination joints and the volume of the copper block.