Numerical Simulation of High-Field Bulk Superconducting Magnet Reinforcement Using Beryllium Copper

Abstract

Trapped fields exceeding 20 T are theoretically achievable in bulk, single-grain high-temperature superconductors (HTS), making them promising candidates for high-field magnet applications. Experimentally, trapped fields above 17 T have been achieved using mechanical reinforcement such as resin impregnation with carbon-fibre wrapping or shrink-fitted stainless steel (SUS). However, because these materials have low thermal conductivity, issues such as localised heating and flux-jump instabilities remain during the magnetization process. This study investigates beryllium copper (BeCu) as an alternative reinforcement, leveraging its superior thermal conductivity and mechanical strength at cryogenic temperatures. A numerical field-cooled magnetization study was conducted using finite-element models to compare the performance of bulk HTS magnets reinforced with either SUS or BeCu rings. Results show that BeCu reinforcement provides higher compressive stress, improved thermal stability, and higher trapped field. The study is extended to simulate a previously reported experiment in which flux jumps limited the trapped field to below 20 T; under identical conditions, replacing SUS with BeCu suppresses flux jumps and maintains thermal stability. Stress analysis reveals that BeCu enables greater pre-stress due to its higher thermal expansion coefficient. Additional simulations under a 25 T applied field demonstrate that BeCu-reinforced magnets could trap over 22 T at 11 K, suggesting enhanced performance and potential for surpassing current bulk HTS magnetization records.