Suppression of Flux Creep in HTS Coil by Applying Low AC Magnetic Field

The suppression of flux creep in the central magnetic field of an high-temperature superconducting (HTS) coil is experimentally validated by applying a low ac magnetic field using additional coils. The HTS coil is fabricated using a Gd-based coated conductor, and a pair of the additional coils wound using copper wires, which are connected in series in the opposite direction, are located coaxially inside and outside the HTS coil. These coils are immersed in liquid nitrogen, and the temporal evolutions of the central fields in the axial direction by applying ac fields for short periods of time using the additional coils after the ramping processes of the HTS coil are observed using a Hall probe. The influences of the amplitude and frequency of ac field on the flux creep in the HTS coil are investigated experimentally.