New IT-Processed Nb3Sn Wires With Cu Alloy Matrix

Abstract

New internal-tin (IT) processed Nb3Sn wires using Cu-alloy matrix instead of pure Cu have been developed. Brass is an attractive alloy as the matrix, because Zn seems effective to accelerate Nb3Sn synthesis. Zn remains homogenously in the matrix after the Nb3Sn synthesis expecting improvement of the mechanical tolerance of the wire, which may be preferable particularly for react and wind magnet applications. Here, two newly designed wires using gold brass (Cu-15wt%Zn) were fabricated: 1) single stack type and 2) multifilamentary (MF) type. Electron probe microanalysis results indicate enhancement of Sn activity in the matrix. Thicker Nb3Sn layers were formed, and residual Sn content in the matrix became smaller compared with Cu matrix samples. The $J_{{{c}}}$ characteristics of the brass matrix wire is appreciably higher than that of the Cu matrix wire. In MF-type wire, inside Nb cores were fully reacted, although unreacted Nb parts were found in outermost filaments. More appreciable reduction of residual Sn content in the matrix was found in the MF-type wire. Present new Nb3Sn wire may be useful for future application of superconductivity.