Screening Currents and Hysteresis Losses in the REBCO Insert of the 32 T All-Superconducting Magnet Using T-A Homogenous Model

The 32 T all-superconducting magnet of the National High Magnetic Field Laboratory (NHMFL) was successfully tested in December 2017 and it is expected to be soon available for users. This all-superconducting magnet, comprised of a high-temperature superconducting (HTS) insert and a low-temperature superconducting (LTS) outsert, is the first superconducting magnet reaching more than 30 T. One of the challenges facing this new magnet technology is the estimation of the screening currents, and the corresponding hysteresis losses in the two HTS coils. These coils are made of more than 20,000 turns of insulated REBCO conductor connected in series. The modelling of such system represents a significant challenge due to the huge computational load imposed by the size of the system. Up to now, only medium size magnets (made of units of thousands of turns/tapes) have been successfully modelled with methods based on the well-known H formulation of the Maxwell's equations. In the present work, a new model based on the T-A formulation and a homogeneous technique is proposed. This new approach greatly reduces the computational load and allows performing real-time simulations of large-scale HTS magnets on personal computers.