Shielding Effect on Flux Trapping in Pulsed-Field Magnetizing for Mg-B Bulk Magnet

T Oka,N Sakai,M Miryala,M Murakami,J Ogawa,K Berger,W Häßler,L Dadiel,K Yamanaka,K Sudo,J Noudem,K Yokoyama

doi:10.1088/1742-6596/1975/1/012019

Abstract

MgB2 superconducting bulk materials are characterized as simple and uniform metallic compounds, and capable of trapping field of non-distorted conical shapes. Although pulsed-field magnetization technique (PFM) is expected to be a cheap and an easy way to activate them, the heat generation due to the magnetic flux motion causes serious degradation of captured fields. The authors precisely estimated the flux trapping property of the bulk samples, found that the flux-shielding effect closely attributed to the sample dimensions. The magnetic field capturing of Ti-5.0wt% sample reached the highest value of 0.76 T. The applied field which reached the centre of the sample surface shifted from 1.0 T to 1.2 T with increasing sample thickness from 3.67 mm to 5.80 mm. This means that the shielding effect was enhanced with increasing the sample thickness. Moreover, Ti-addition affected the frequency of flux jump happenings. The occurrence of flux jumps was suppressed in 5.0wt%Ti-added sample. This means that the heat capacity of the compounds was promoted by Ti addition.

Highlights

IntroductionThe field-trapping principle of high temperature superconducting bulk materials (hereafter abbreviated as HTS bulk magnets or bulk magnets) is different from that of conventional permanent magnets such as Nd-Fe-B or ferrite magnets [1], [2], [3]
The field-trapping principle of high temperature superconducting bulk materials is different from that of conventional permanent magnets such as Nd-Fe-B or ferrite magnets [1], [2], [3]
Plotted lines aligned parallel to each other, which means that the shielding effect remains as it was to its high field region

Summary

Introduction

The field-trapping principle of high temperature superconducting bulk materials (hereafter abbreviated as HTS bulk magnets or bulk magnets) is different from that of conventional permanent magnets such as Nd-Fe-B or ferrite magnets [1], [2], [3]. Since the trapped field of bulk magnets are roughly simulated as what we call pancake coils, one can obtain extremely intense magnetic field by flowing the intense current to the coils composed of superconductors because the electrical resistivity is negligible. Meltgrown bulk materials are regarded as a sort of non-insulated coils. Both systems may be characterized by the rearrangement of superconducting current. Beside the rare earth-based compounds (REBa2Cu3O7-y system, RE means rare earth elements), MgB2 bulk materials are characterized as its uniform crystal structure and resultant uniform field trapping [8]. The Tc is low as 39 K, the field distribution with no distortion brings its advantageous applications which demand homogeneous field spaces [9], [10], [11]

Methods

Results

Conclusion