Shield Effect of a Powder-Metallurgy Processed Nb₃Sn Superconductor

Abstract

Powder-metallurgy processed Nb₃Sn composite has been studied aiming at the practical application of magnetic shielding. The composite was fabricated using a mixture of gas-atomized bronze (Cu-10wt% Sn) powder and hydride-dehydride processed Nb powder which passed through a sieve with an opening size of 50μm. The mixture was compacted by a hot isostatic press and heat-treated to form the Nb₃Sn composite. A three-dimensional network consisting of Nb₃Sn shells and a three-dimensional network of bronze were observed in the composites. Magnetic shielding properties of the composites were invesitgated using cylindrical samples with an outer diameter of 24mm, an inner diameter of 6.7mm and a height of 43mm. It was found that the cylindrical samples reduced inhomogeneous field without a flux jump in an alternating field with a rate of 0.1T/min up to 1-2T. In three kinds of cylindrical samples, composites with a volume fraction of bronze of 0.2, 0.25 and 0.3 in the starting mixture, the stability of the cylindrical sample for the hysteresis loss increased and the maximum external field strength to be shielded increased as the fraction of bronze rose.