Development of a Desktop-Type Superconducting Bulk Magnet

We developed a desktop-type superconducting bulk magnet using a Stirling cryocooler with the aim of miniaturizing the system. This refrigerator was compact and highly energy efficient because a compressor was not needed outside; power consumption was approximately 160 W. Moreover, the length of the magnetic pole was decreased by restricting the activation method to pulsed field magnetization. A GdBCO bulk material 45 mm in diameter and 20 mm thick was attached to the cold stage of a refrigerator and was covered with a vacuum chamber. The sample was cooled from room temperature to 52.3 K in approximately 4.5 h. When a single pulsed field was applied in amplitudes varying from 0.8 to 7.0 T, the maximum trapped field was approximately 2.8 T at the center of the bulk surface in the applied field of 7.0 T. Moreover, the maximum magnetic field on the chamber's surface was approximately 1.3 T, and the total magnetic flux was 0.94 mWb. The operational status after magnetization was good, and the operating sound was small.