Toward Optimization of Multi-Pulse, Pulsed Field Magnetization of Bulk High-Temperature Superconductors

Abstract

Pulsed field magnetisation (PFM) is the most practical method for magnetising bulk superconducting materials as trapped field magnets (TFMs), but the record trapped field achieved by PFM to date is still significantly less than the true trapped field capability of these materials. In this paper, a flexible numerical modelling technique based on the finite element method is used to provide a comprehensive and realistic picture of multi-pulse PFM, which has been shown to be effective in increasing the trapped field/flux over a single pulse. Firstly, the maximum trapped field capability of a representative sample is determined using two types of numerical model simulating fieldcooling (FC) and zero-field-cooling (ZFC) magnetisation. Next, various sets of magnetic field pulses are applied to the bulk to analyse multi-pulse PFM. An increase in the trapped field can be achieved after a 2 nd pulse and to do so an increased amplitude of applied field is required to maximize the trapped field fully. The numerical analysis shows that this occurs in subsequent pulses because it is more difficult for the magnetic flux to penetrate the sample and there is a lower temperature rise.  Index Terms-Bulk high-temperature superconductors, finite element method, numerical simulation, pulsed field magnetization, trapped field magnets. I. INTRODUCTIONULK superconducting materials can be used as trapped field magnets (TFMs) and magnetic fields greater than 17 T have been achieved in large, single-grain (RE)BCO (where RE = rare earth or Y) bulk high-temperature superconductors [1], [2]. However, developing practical magnetising techniques is crucial to using them as TFMs in engineering applications, such as rotating machines, magnetic separation and magnetic drug delivery systems [3]- [5].Pulsed field magnetisation (PFM) is the most practical M. D. Ainslie would like to acknowledge financial support from a Royal Academy of Engineering Research Fellowship and an Engineering and Physical Sciences Research Council (EPSRC) Early Career Fellowship EP/P020313/1. Additional data related to this publication are available at the University of Cambridge data repository (

Flux Dynamics and Thermal Behavior of a GdBaCuO Bulk Magnetized by Single- and Double-Pulse Techniques Using a Split-Type Coil

“…These results are similar to that for S-sol(25 K) and D-sol(65 K, 25 K). These results support the previous reports, in which the multi-PFM using the solenoid-type coil enhances the trapped field [8], [15].…”

“…These results are similar to that for S-sol(25 K) and D-sol(65 K, 25 K). These results support the previous reports, in which the multi-PFM using the solenoid-type coil enhances the trapped field[8],[15]. Fig.4(a) shows the maximum temperature rise, ΔTmax, during PFM, as a function of the applied pulsed field (Bex), for each sequence using the split-type coil.…”

“…Similarly to the split-type coil, Rin for D-sol is smaller than that for S-sol. The double-PFM by both magnetizing coils results in a decreased Rin value, because it is more difficult for the flux to penetrate the bulk due to the existence of the flux trapped from the 1 st pulse [15]. Fig.…”

“…ΔTmax increased with increasing Bex for all cases. The ΔTmax value of the double-PFM is lower than that of the single-PFM, which results from lowering the flux pinning and viscous losses due to the already trapped magnetic flux after the 1 st magnetic pulse application [7], [15]. The ΔTmax value using the solenoid-type coil, shown in Fig.…”

Influence of <italic>J</italic>c(<italic>B</italic>, <italic>T</italic>) Characteristics on the Pulsed Field Magnetization of REBaCuO Disk Bulks

“…However, the trapped field by PFM is much lower than that by FCM because of a large temperature rise due to the rapid and dynamic motion of magnetic flux. There have been several improvements made experimentally and numerically for the PFM technique to enhance the trapped field; the insertion of soft iron yoke from a magnetic point of view [1], and the multi-pulse application from a thermal point of view [2,3]. The trapped field of TFMs by PFM is determined by a complex relationship between Jc(B, T), the thermal properties (specific heat and thermal This research is partially supported from JSPS KAKENHI Grant No.…”