Anisotropic in-plane field angle dependence of critical current in commercial REBCO tapes and its impact on toroidal field magnet for compact tokamak fusion device

Abstract

Abstract The critical current (I c) of commercial rare-earth barium copper oxide (REBCO) tapes is generally assumed to exhibit isotropic behavior with respect to the magnetic field angle applied within the tape’s basal plane (in-plane). This paper investigates the field angle dependence of critical current, both in-plane and out-of-plane, for commercial REBCO tapes manufactured by SuperOX, under fields ranging from 0 T to 8 T at 20 K. Remarkably, the in-plane field angle dependence of I c shows significant anisotropy, with the minimum I c no longer occurring at the traditional 90° (parallel to the ab-plane), but instead shifting to approximately 130°, a phenomenon reported for the first time. This novel anisotropic in-plane field angle dependence of I c can substantially affect the performance of toroidal field magnets for compact tokamak fusion devices. Simulations indicate that considering versus neglecting the anisotropic in-plane field angle dependence of I c can lead to I c variations of up to 19.58% within the D-shaped coils of the toroidal field magnets. The locations of maximum deviation vary across different double-pancake coils within the D-shaped winding packs. This study highlights the complexity of I c distribution in toroidal field magnets for compact fusion applications, urging further consideration of anisotropic in-plane field angle dependence of I c of commercial REBCO tapes in fusion magnet design.