Rise-time elongation effects on trapped field and temperature rise in pulse field magnetization for high temperature superconducting bulk

Pulse field magnetization (PFM) using a magnetic pulse of B_ex = 3.83-5.53 T with various rise times t_r (= 6-20ms) has been performed for the cryocooled SmBaCuO bulk superconductor starting at the initial temperature of 40 K. The time evolutions of temperature T(t) and local field B_L^P (t) have been measured on the bulk surface after applying the magnetic pulse. With increasing t_r, the temperature rise ΔT and the trapped field B_T^P increase for B _ex ≤ 4.70 T and decrease for B_ex = 5.53 T. The rise time t_r required to realize the optimum B_T^P has been found to become longer for a smaller pulse field B_ex. From the analyses of the generated heat Q after five successive applications of pulses (Nos. 1-5) with the same amplitude, the Q(No. 5) value, which can be regarded as the viscous loss Q_v, decreases with increasing t_r, due mainly to the decrease in the flux propagation velocity v in the bulk with longer t_r.