Study on three-dimensional flux dynamics in bulk superconductor for improving its magnetization performance

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RE-Ba-Cu-O bulk superconductor has the good flux-pinning property and is expected to be applied as a high flux source. For such an application the pulsed field magnetization is an important technique and its performance improvement is required. This study aims at examining flux dynamics during the pulsed field magnetization process, clarifying flux motion and induced current distribution when a pulse magnetic field is applied to bulk superconductor with spatially inhomogeneous superconducting properties, and considering performance improvement of pulsed field magnetization. Both experiments and numerical analysis were carried out.In the experiments search coils and a hall probe were used to measure the variation of flux density distribution during the pulsed field magnetization and the resultant trapped flux density distribution. The results have clarified the relation between the flux density distribution and the applied magnetic fields. For numerical analysis, a analysis tool for axi … More symmetric three-dimensional coupled problems of electromagnetic and temperature fields has been developed with the voltage-current characteristics of bulk superconductor and the dependence of its critical current density on magnetic flux density and temperature taken into account under the cooling conditions of immersion cooling by liquid nitrogen and conduction cooling by a cryocooler. In addition full three-dimensional analysis was also carried out and discussed for several cases. With these analysis tools and models the numerical analysis of pulsed field magnetization process of bulk superconductor were performed under the various conditions. The analysis results qualitatively agreed with experimental results, and indicate that the analysis tools and models can be used for the detailed analysis of electromagnetic phenomena and temperature distribution in the superconductor.From these experimental and analysis results the flux motion and dynamics in bulk superconductor during pulsed field magnetization has been discussed and clarified. Less