Study of NbTi Superconducting Strands for JT-60SA Toroidal Field Coils

JT-60SA is a fusion experiment designed to support the operation of ITER and to investigate how best to optimize the operation of fusion power plants that are built after ITER. The toroidal field (TF) coils uses the Cable-in-conduit Conductor (CICC) with NbTi superconducting strands. The TF coils will operate at with 25.7 KA @5.65 T, 4.9 K. Western Superconducting Technologies Co., Ltd. (WST) has studied two types of NbTi superconducting strands for the JA-60SA TF coils. The strands choose the internal CuNi alloy for the internal resistive barrier, which is expected to calibrate and control the inter-strands resistances and to better current distribution between strands in CICC. The strand samples were tested in the range of 4 11 T magnetic field at 4.22 K for critical current, and 5.7 K 6.4 K at 5.65 T for current sharing temperature. This paper presents the results on critical current(Ic), critical current density (Jc), current sharing temperature (Tcs), and hysteresis loss of the strands.