Multipoint Measurements of Transient Flux Motion on Bulk Superconductor During Pulsed Field Magnetization

Recently, various apparatuses using magnetized bulk superconductors as strong flux sources have been studied. The Pulsed field magnetization (PFM) is expected as an effective method for magnetizing the bulk superconductor. The applications using the PFM would make the magnetization system much simpler than the other methods. However, in the PFM, the inhomogeneity of the magnetized distribution becomes a problem when the bulk superconductor is applied to various apparatuses. The recent researches have revealed that such inhomogeneity strongly depends on the local critical density distribution. In the local region with the lower critical current density, the magnetic flux penetrates the bulk superconductor more easily. We study the transient electromagnetic phenomena of the local magnetic flux motions during the PFM by using multi-pick-up coils arranged on the whole surface of the bulk superconductor. In this study, we quantitatively evaluate local motions of magnetic flux in bulk superconductor. A complex magnetization process during the PFM is clarified based on the inhomogeneous distribution of the critical current density in the bulk superconductor.