Magnetizing Performance Evaluation of HTS Bulk Magnet Using a 12 K Refrigerator with High Cooling Capacity

We study a high magnetic field generation using HTS bulk magnets activated by pulsed-field magnetization with the goal of their industrial application. In our previous study, a single-stage GM-type refrigerator and a two-stage GM-type refrigerator with an air-cooled-type compressor and a Stirling refrigerator were used for cooling an HTS bulk aiming at simplifying the bulk magnet system. Now, we developed a new bulk magnet system using a two-stage GM-type refrigerator with a high cooling capacity of 12 W at 20 K aiming to enhance a trapped field by improving the cooling ability. When a GdBCO bulk 60 mm in diameter and 20 mm thick was cooled from the room temperature to the lowest, the lowest temperature was 13.3 K at the sample stage and 45.5 K at the bulk surface for 3.5 h. When a single pulsed field was applied with varying the amplitude and temperature, the maximum flux densities of 3.59 T on the bulk surface and 2.34 T at the pole surface, and the total magnetic flux of 2.48 mWb were achieved at 20 K.