Generated heat during pulse field magnetizing for REBaCuO (RE = Gd, Sm, Y) bulk superconductors with different pinning abilities

Abstract

Pulse field magnetizing (PFM) using five successive magnetic pulses (Nos 1–5) with the same amplitude from 3.01 to 5.42 T has been performed for three types of cryo-cooled REBaCuO bulk superconductor discs (RE = Gd, Sm, Y) with an identical size. The time evolution and spatial distribution of temperature T(t), the total trapped magnetic flux ΦTP and the trapped magnetic field BTP have been measured after applying the magnetic pulse. The total magnetic flux ΦTFC trapped by the field cooled magnetizing (FCM) is the largest for the Gd bulk and is the smallest for the Y bulk. The time and position dependences of T(t) during PFM show a characteristic behaviour depending on the species of bulks which results from the difference in the strength of the pinning force Fp. The generated heat Q(No i) after the No i pulse has been estimated based on the maximum temperature rise ΔTmax and the specific heat C. The ΔQ = Q(No 1)–Q(No 5) value, which is mainly contributed by the pinning power loss (Qp) for pulse No 1, is the smallest for the Y bulk, and the Q(No 5) value, which is mainly contributed by the viscous flow loss (Qv), is the smallest for the Gd bulk. These results suggest that the heat generation by PFM is closely related to the strength of Fp of the bulk crystal.