Thermal Stability Study of a Solder-Impregnated No-Insulation HTS Coil Via a Raman-Based Distributed Optical Fiber Sensor System

Mechanical stability of no-insulation (NI) high-temperature superconducting (HTS) coils will be greatly enhanced after using a solder impregnation (SIM) method. For superconducting high-field magnet applications, besides the mechanical stability, the thermal stability of SIM coils is also a crucial parameter which needs to be investigated. Due to its high insulation, convenient installation, distributed temperature measurement, and insensitive to stress, a Raman-based optical distributed temperature sensor (RmDTS) system is an ideal option for monitoring the temperature of SIM coils. In this study, an NI HTS coil and an optical fiber were successfully impregnated together by solder. The critical current of SIM coil determined by the central magnetic field is 69 A. To create quench process, a dc current of 240 A was injected into an SIM coil, and the temperature of the coil was monitored by the RmDTS simultaneously. The test results show that the temperature of the SIM coil was unchanged although a four times Ic was applied.