Influence of Soft-Iron Yoke Thickness on the Magnetizing Characteristics of a Bulk Magnet Excited by Pulsed-Field Magnetization

We try to generate a high magnetic field by activating an HTS bulk with pulsed-field magnetization (PFM). By using a soft-iron yoke, a trapped field can be improved due to exposing a large amount of magnetic flux to the bulk for a long time because the applied field decreases slowly after reaching a peak as compared to the case without the yoke. However, the total weight of the system increases, resulting in a decrease of power density. We study the influence of the yoke on magnetizing characteristics and previously carried out PFM experiments using pure-iron yokes with different diameters and shapes. This paper investigates the influence of yoke thickness experimentally and numerically. The thicker the yoke, the larger the maximum value of applied flux density becomes; furthermore, a total applied flux during the excitation can be increased. As a result of magnetizing a GdBCO bulk by using yokes with diameters of 64 mm that are 5, 10, 20, 30, and 47 mm thick, the total magnetic fluxes of the t30, t20, t10, and t5 yokes were 96%, 89%, 81%, and 73% of that of the t47 yoke, respectively. These results indicate that the trapped magnetic field characteristics are highly dependent on the yoke thickness.