Influence of Artificial Defects on Trapped Field Performance in a Superconducting Bulk Magnet

In this study, we attempt to improve the trapped magnetic field by pulsed-field magnetization using REBCO bulk with small holes processed artificially. In our previous study, a hole was opened in the growth sector region (GSR) in accordance with the idea that the performance of the growth sector boundary (GSB) was not reduced because the critical current density of the GSB was higher than that of the GSR. In the next study, a small hole was processed on the GSB to decrease the magnetic shield toward the magnetic flux that entered through the GSB. The experimental results suggested that placing a hole on the GSB was advantageous to trapped field performance as compared with placing a hole at the GSR. In this paper, three more holes were processed in the bulk with a single hole on the GSB, and trapped field performance was investigated. Although the performance was decreased overall in the bulk with four holes, we confirmed that the peak value of total magnetic flux shifted to the low applied magnetic field, although the maximum value was almost the same as that of the bulk with a single hole.