Experimental Studies of Current Decay in a Flux Pumped HTS Magnet Subject to Travelling Magnetic Fields

Superconducting magnet, which provides a steady magnetic field if operated in persistent current mode (PCM),can he applied in MRI/NMR, motors, and other power devices. However, due to the joint resistance of high temperature superconducting (HTS) magnet manufactured by coated superconducting tapes, it would be difficult to realize PCM operation. Moreover, the ac loss would affect the decay characteristics of HTS magnet when applied in the ac magnetic field circumstance. In this paper, a shorted racetrack HTS magnet was manufactured and charged by a flux pump. The current decay of the pumped HTS magnet with and without travelling magnetic field was investigated. Results show that subjected to travelling magnetic field, the current decay of the PCM HTS magnet cannot be simply explained by the existence of joint resistance, other factors, which are more important, must be figured out. To understand the underlying mechanism, the dynamic resistance explanation has been adopted and verified by numerical calculation.