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) (= 6-20 ms) 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(P)(L)(t) have been measured on the bulk surface after applying the magnetic pulse. With increasing t(r), the temperature rise Delta T 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(P)(T) 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 tr, due mainly to the decrease in the flux propagation velocity v in the bulk with longer t(r).