Trapped Flux and Current Density Distributions of a 140Â mm Diameter Large Single-grain Gd-Ba-Cu-O Bulk Superconductor Fabricated with RE Compositional Gradient Method

We studied the trapped flux and current density distributions of a large single-grain Gd-Ba-Cu-O bulk superconductor fabricated with RE compositional gradient method. The diameter of the bulk is 140 mm and its thickness is 20 mm. Field cooling of the bulk was performed in an external magnetic field of 3.5 T at 77 K. The maximum trapped flux density at 0.94 mm above the bulk was about 2.6 T. The peak effect was observed near the center of bulk. An inverse problem analysis was also carried out to estimate the current density distribution in the bulk from the trapped flux density distribution. It was estimated to be around 1.0×108 A/m2.