AC Loss Reduction in HTS Magnets by Applying Superconducting Shielding Coils and Magnetic Flux Diverters

A 10 T fast-ramping high-temperature superconducting (HTS) magnet is being designed to characterize new rare-earth permanent magnet materials. However, AC loss associated with the fast-ramping process is one of the key technical challenges. This study focuses on evaluating the effectiveness of loss-reduction strategies—superconducting shielding coils (SSC) and magnetic flux diverters (MFD)—both individually and in combination. As the first step of the project, AC loss in a small-scale magnet was numerically studied, resulting in loss reduction of approximately 32%, 71%, and 90% with SSC, MFD, and their combination, respectively. By analyzing the correlation between critical current and AC loss, we found that the frequency and amplitude of the transport current significantly influence the effectiveness of SSC. In the subsequent simulation for the 10-T magnet, AC loss reduction is up to 34%, 57%, and 71% when using SSC, MFD and both. The simulation results indicate that the effectiveness of SSC is less sensitive to high magnetic fields than that of MFD; MFD is still effective for the 10-T magnet, even beyond its saturation field; the combined configuration of SSC and MFD is the most efficient method for AC loss reduction.