Investigation into quench detection for a mutli-stacked pancake coil wound with Nb3Sn CIC conductors

For a multi-stacked (MS) pancake coil wound with Nb3Sn CIC conductors, quench detection methods using voltage measurements were investigated. In this study, we utilized two methods: the balanced voltage between two coil windings and the balanced voltage between one coil winding and a disk-shaped pickup coil. During the energization of the MS pancake coil, voltage measurements of the coil were conducted to compare the measurement results of the two quench detection methods. The measurement results indicate that the quench detection based on the balanced voltage between two coil windings is more reliable than the other.In the measurements, spike voltages were observed when there was a rapid change of a coil current. Magnetization of the MS pancake coil is considered one cause of the spikes. When determining criteria of quench detection, spike voltages should be taken into account to prevent malfunction of a quench detection system.28th International Toki Conference on Plasma and Fusion Research (ITC-28