AC Loss and Temperature Margin of Cable-in-Conduit Conductors for JT-60SA Poloidal Field Coil

Three kinds of conductors for JT-60SA poloidal field coil are evaluated: (1) a cable consists of Nb₃Sn superconducting strands and pure copper strands (CS conductor); (2) a cable consists of only NbTi superconducting strands (EF-H); and (3) a cable consists of NbTi superconducting strands and pure copper strands (EF-L). We measured the AC loss under a time-varying external magnetic field. The AC loss experiment on these conductors was carried out with a calorimetric method. As a result, the coupling time constant of CS, EF-H, and EF-L conductors was 50, 45, and 40 ms ( nτ = 100, 90, and 80 ms), respectively. The obtained results become fundamental data to estimate the current sharing temperature margins (Tcs) of the conductor.