Racetrack-Shaped HTS Coils With Metal-as-Insulation: Transient Behavior Model and Experimental Validation Status

Abstract

High Temperature Superconductors (HTS) offer significant potential for very high field application, thanks to their high current density. However, the high thermal stability make the protection of such magnets challenging. This is why CEA is exploring the use of specific No-insulation (NI) technology — and more precisely Metal-as-Insulation (MI) technology — to implement a protection layer within the design phase. The transient behavior of the REBCO combined with this NI or MI technology needs to be quantified at high magnetic fields to ensure the effectiveness of the protection. Following this goal, a dedicated Partial Element Equivalent Circuit (PEEC) model has been developed for several years at CEA and has been updated recently with the addition of racetrack shaped coils. Our PEEC model allows us to simulate multiples racetrack-shaped coils with different parameters such as power supply current, voltage limitation, local degradation, heaters, and external magnetic fields. To validate this model, we built coils samples. The dimensions of the samples were thoroughly chosen to allow meaningful comparison with the model. Preliminary tests have been performed in a liquid nitrogen bath (77 K) and in self-field configuration. Moreover, to validate the behavior of the coils when a local degradation is applied, it is required to control this defect accurately. Therefore, we also conducted an experimental study to control the size and level of degradation we apply on the tape. These data enable us to provide precise inputs for our numerical simulations.