Study on Hot-Spot Temperature Limits for YBCO Epoxy-Impregnated Coil to be Safe From Damages Caused by Quenches

Hot-spot temperature limits for YBCO epoxy-impregnated coil to be safe from damages caused by quenches are experimentally investigated using small-scale test coils. In the authors' previous study, it is found that the hot-spot temperature limits for YBCO paraffin-impregnated coils are around 500 K where the critical current of YBCO wire is degraded thermally. However, in the cases of the epoxy-impregnated coils, it is shown that the hot-spot temperature limits are around 300 K, much lower than those of the paraffin-impregnated coils. In this paper, a reason for those lower hot-spot temperature limits of the epoxy-impregnated coils is discussed.