A homogenised anisotropic J-model for accelerating computations of screening current profile in large-scale HTS magnets

Abstract

Abstract Owing to the induced excessive strain, plastic deformation, and distortion of the magnetic field in high-temperature superconducting (HTS) tapes, there is a rapidly growing research interest in the screening current profile in high-field superconducting magnets. The J-model was developed to calculate the current density distributions in HTS stacks and cables, which improves the calculation efficiency because no air domain is considered in the calculation regions. However, for a large-scale high-field magnet wound with hundreds and thousands of layers of HTS tapes, there is still a big challenge for J-model simulation involving prohibitive time consumption and memory requirements. This study proposes an improved J-model approach based on a homogenised anisotropic (HA) scheme for large-scale HTS magnet systems to decrease the number of elements and enhance calculation efficiency. The reliability of the improved HA J-model was verified by solving 2000-tape HTS stacks, and a significant improvement in computational performance was achieved. Furthermore, the HA J-model was applied to a large-scale scenario of a 32 T hybrid all-superconducting magnet at the National High Magnetic Field Laboratory to numerically capture the electromagnetic responses. The magnetic flux and current densities in the HTS insert coils were obtained completely, and the screen current induced field, which is the most concerning, showed a good agreement with the literature. Meanwhile, the time consumption by the HA J-model is approximately half that of the traditional J-model and even less than 1–2 orders of magnitude of the others, such as the traditional T-A model and H model, with acceptable accuracy. The improved HA J-model may provide an appropriate prior design with rapid and real-time calculations for large-scale magnet systems.