Evaluation of the Thermal Stability of REBCO Pancake Coils With Partially Noncontact Areas Between Winding Turns

We have been developing REBCO coil systems for high-magnetic-field whole-body MRI and accelerator for cancer therapy. To achieve high thermal stability and high current density, we have focused on no-insulation (NI) coils, in which REBCO tape is wound without electrical insulation. In actual coil windings, areas of insufficient contact may exist between turns, thus making it impossible to take advantage of the characteristics of the NI coil. In addition, when winding large diameter pancake coils assuming aforementioned applications, multiple REBCO tapes must be connected together in series. In this study, numerical analysis was performed based on the partial element equivalent circuit (PEEC) model to evaluate the transient stability of the NI-REBCO pancake coil using the number, length, and location of turn-to-turn noncontact areas between turns as parameters. Especially in this paper, we focus on the influences of Cu stabilizer thickness and the joints between REBCO tapes.