Development of High-Performance Cu-Nb/Nb₃Sn Wires for Various High Field Magnets

The bronze processed Nb3Sn wires strengthened with the Nb-rod-method Cu-Nb stabilizing reinforcer have excellent mechanical strength and a large compressive residual strain at both low temperatures and room temperatures after Nb3Sn reaction heat treatment. Therefore, the Cu-Nb/Nb3Sn wires are able to be applied to the high field superconducting magnet manufacturing by techniques of the React-and-Wind (R&W) and realize the higher irreversible strain. The characteristics such as the critical current density and the strength of Cu-Nb/Nb3Sn wires are designed to meet the required specifications by selecting tin content in the bronze, Nb volume ratio in the Cu-Nb composites, and the Cu-Nb volume ratio. For the R&W process, appropriate pre-bending treatments are applied to optimize the Icproperties under various stresses. In this study, a round Cu-Nb/Nb3Sn wire design was optimized for high-strength Rutherford cables used under high tensile stress over 300 MPa by composing of Cu-15.7wt%Sn-0.3wt%Ti and Cu-30vol%Nb stabilizing reinforcer. Moreover, a R&W-type Cu-Nb/Nb3Sn rectangular wire was proposed to improve the performance of the ultra-high field NMR coils.