Statistics on AB-Plane Offsets in REBCO Coated Conductors and Implications for Non-Twisted Magnets

The critical current (I_c) of 2G REBa₂Cu₃O_7-x (REBCO) high temperature superconductors (HTS) is highly anisotropic with respect to the applied magnetic field (B), with a strong I_c peak expressed at B||ab-plane of the HTS crystal structure. However, as manufactured, there is typically a small-angle ab-plane tilt offset relative to the plane of the tape, and a large average offset can significantly affect magnet I_c if unaccounted for, especially in non-twisted coils such as the SPARC toroidal field magnets being developed by Commonwealth Fusion Systems (CFS). To address this issue, the statistics of the magnitude and orientation of the ab-offset were studied on quick time scales in production quantities for two different HTS vendors by X-Ray Diffraction (XRD) using (005) rocking curves, and the offset was observed to be vendor dependent. The data were correlated positively with offsets determined by SEM, and to I_c at low temperature and moderate to high field by transport and torque magnetometry.