Trapped Flux Dependence of Bulk High-Temperature Superconductors Between 77 and 30 K under a Limited Excitation Field
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The trapped-flux dependence of bulk high-temperature superconductors between two typical working temperatures of 77 and 30 K was investigated by a field-cooling magnetization (FCM) method under a limited excitation field of 5 T to approach actual application conditions. An exponential trapped-flux dependence between the two temperatures was obtained by fitting the experimental data. Its effectiveness was checked from the theoretical temperature relationship of the critical current density and trapped-field data in the literature. It was found that the achievable trapped flux at 30 K is closely dependent on the excitation field. The bulk samples with moderate performance around the trapped-field range of 1.0–1.5 T at 77 K can be efficiently activated to reach a trapped field over 4.6 T at 30 K. Bulk samples with better performance at 77 K will get saturation and cannot be fully excited by the 5 T excitation field. The presented results are useful for the appropriate estimation of trapped-flux performance from 77 to 30 K and may support some basic references for the applications of bulk HTS magnets.
KeywordsHigh-temperature superconductors Trapped magnetic flux Field-cooling magnetization Working temperature Excitation magnetic field
The authors are grateful to Adelwitz Technologiezentrum GmbH (ATZ) in Germany for providing the bulk HTS samples. This work was partially supported by the Grant-in-Aid for Japan Society for the Promotion of Science (JSPS) Fellows (P09305), the Grant-in-Aid for Scientific Research (KAKENHI, 2109305 and 21360425) and the basic applied research plan of Yunnan Province (2012FD051).