Evaluation of pulsed-field magnetization of a bulk superconductor with small holes

Recent upsizing of the diameter and enhancement of performance of bulk superconductors make pulsed field magnetization difficult due to the strong magnetic shield. We propose a bulk material with small holes to supply magnetic flux into the bulk efficiently because superconductivity is intentionally lowered in the portion with holes. On the other hand, we are anxious about the flux flow in a high applied field. To investigate the effect of the proposed method, a bulk material with small holes was manufactured, and a fundamental experiment was carried out. Four holes of 2 mm in diameter were drilled in a growth sector region of a GdBa₂Cu₃O_7-x bulk material of 60 mm in diameter and 20 mm thickness. The holes were filled with solder to improve mechanical strength and heat conduction. The bulk was cooled to 20, 30, 40, and 50 K, and a single pulsed field was applied while changing the amplitude of the applied field at each temperature. It was confirmed that the magnetic flux penetrates at a low applied field as compared with the holeless bulk material, and, moreover, the flux flow was suppressed in a high applied field at a low temperature.