Flux trapping behavior in a joint-less closed-loop 2G-HTS coil under multi-pulse magnetic field excitation

Second-generation high-temperature superconducting (2G-HTS) magnets operating in persistent current mode (PCM) hold great promise for applications such as magnetic resonance imaging. The development of joint-less closed-loop magnets has effectively tackled the challenges of fabricating joints for REBCO tape. However, certain closed-loop magnets cannot utilize conventional persistent current switches (PCS) and instead require multi-pulse magnetization techniques. This study explores the effects of multi-pulse magnetic field excitation on the flux trapping behavior of a four-pancake coil (FPC). A detailed comparison of the effects of different pulse types and periods on the FPC reveals that the background magnetic field exceeds the critical magnetic field of the coil, thereby creating resistance in the superconducting loop. The critical magnetic field of the FPC is determined experimentally, and a reasonable speculation on the multi-pulse field excitation mechanism is presented.