Effect of magnetic field angle, cabling deformation and transverse loading on ITER Nb₃Sn strand hysteresis loss

For the ITER superconducting magnets, evaluation of their AC losses with computer models is essential for the preparation of the ITER magnet system commissioning and operation. A benchmarking effort on the recently tested CS Module 2 and 6 cold test AC loss data, revealed a significant discrepancy between model and experiment. For better understanding, the magnetization is measured on virgin strands and compared with AC loss of full-size CS CICCs in virgin condition and after being subjected to transverse load cycling. Eleven different ITER Nb3Sn strand types are tested in a Vibrating Sample Magnetometer (VSM) for different angles between strand axis and magnetic field orientation. In addition, few longer strand samples with different winding density were tested in the Twente magnetometer for comparison to short VSM sample results. The comparisons serve to evaluate the potential impact of cabling, transverse load strand damage, demagnetization and field angle. It was found that these effects were not large enough to explain the discrepancy between short sample measurements and model at one side and CS module loss at the other side.