AC loss measurement of 46 kA-13T Nb3Sn conductor for ITER

AC Losses of Nb3Sn conductor samples with various void fractions for the ITER Central Solenoid Model Coil (CSMC) were measured by using calorimetric and magnetization techniques. The CSMC is designed to generate the magnetic field of 13 T at the operating current of 46 kA, The conductor consists of the multi-stage cable, having 1152 Nb3Sn strands, and Incoloy 908 square jacket with circular hole. The strands are coated by chrome plating with 2 mum layer, The last sub-cables are wrapped with Inconel tape, having high electric resistivity, to reduce the coupling current loss. The optimum void fraction for pulse coils is obtained from the relation between the coupling time constant and the void fraction. It is indicated that the sub-cable wrapping is very effective in limiting the coupling current between the sub-cables, as expected. The AC losses of the CS insert were measured in various operating modes. From these obtained results, the validity of conductor design is demonstrated.