Effect of resin layer on the thermal stress of bulk superconductors

We studied how the field-trapping capability decays with the number of trapped-field measurements for bulk Y-Ba-Cu-O samples with and without resin impregnation. The field-trapping capability decayed with the number of measurement for a bare bulk superconductor, while no degradation was observed in the bulk impregnated with resin. We then performed numerical simulations for the thermal stresses of such bulk superconductors using the finite-element method. The thermal tensional stress of a bulk Y-Ba-Cu-O without resin reached 224 MPa, while that of the bulk covered with resin 0.5 mm in thickness was only 27 MPa. This was responsible for an improved durability against repetitive thermal cycles in the sample with resin impregnation.