Critical Current Densities of Multifilamentary Nb₃Sn Conductors by Internal Diffusion Method

Abstract

Multifilamentary Nb₃Sn composite conductors with submicron filament diameters have been developed by the internal tin diffusion method. The heat treatment condition to optimize the critical current density was studied in detail. The different heat treatment was performed in two stages according to the arrangement of the copper clad tin cores in strands. The first stage is for the homogenization heat treatment (HHT) of tin in the copper matrix. In the second stage, the reaction heat treatment (RHT) of Nb₃Sn was applied. With a suitable combination of HHT and RHT, Nb₃Sn with a critical current density high enough for a.c. use was formed at a reaction temperature as low as 350°C.