Influence of the Shape of Soft-Iron Yoke on Trapped Field Performance of HTS Bulk

We investigate the influence of soft-iron yokes on the magnetizing characteristics of HTS bulk magnet excited by pulsed field magnetization (PFM). By using the yoke, the trapped field could be improved because the bulk was exposed to the magnetic field for a long time due to hysteresis characteristic. In our previous study, a magnetizing test was performed by using the yokes with different size, resulting that the trapped field of a large yoke was higher than that of a small one. In this study, an effect of the shape of yoke on trapped field performance was evaluated quantitatively. A GdBCO bulk 60 mm in diameter and 20 mm thick was magnetized by using the disk-, ring- and cross-shaped yokes. The trapped field of the cross-shaped yoke was the highest, and that of the ring-shaped yoke was the smallest. However, when the total magnetic flux per unit weight of the yoke was compared, its value of the ring-shaped yoke was a little higher than that of the disk-shaped one. These results provided the possibility of reducing the weight of the system while maintaining the high trapped field by decreasing the volume of soft-iron yoke.