Multifilamentary Nb3Sn Wires Fabricated Through Internal Diffusion Process Using Brass Matrix

Abstract

New multifilamentary Nb 3 Sn wires have been fabricated through an internal diffusion process using brass matrix. Brass has not only good elongation characteristics but also high yield strength more than double compared with Cu. Electron probemicroanalysis results show good interdiffusion between Sn and brass during the heat treatment. Zn remains homogeneously in the matrix after the Nb 3 Sn synthesis, expecting improvement of the mechanical strength of the wire. High mechanical strength would be preferable, particularly for react & wind magnet applications. Moreover, Zn seems effective to accelerate the Nb 3 Sn synthesis. The Nb 3 Sn layer in the brass matrix sample is more than 60% thicker than that in the reference Cu matrix sample. The thicker Nb3Sn layer accounts for the higher critical current density J c of the brass matrix sample. The B c2 of the wire is estimated to be about 25.5 T at 4.2 K. The volumetric ratio of Nb, Sn and Cu-Zn matrix has not yet optimized in terms of .Ic characteristics. The grain morphology of the Nb 3 Sn layer exhibits almost no difference between brass and Cu matrix samples. In order to improve the non-Cu .Ic characteristics, a newly designed wire has been developed.