Nb-rod-method Cu–Nb/Nb₃Sn wires for practical react-and-wind applications

Bronze-processed Nb₃Sn-based wires reinforced by Nb-rod-method Cu–Nb composite (Cu-Nb/Nb₃ Sn) are applicable to react-and-wind (R&W)-processed Nb₃ Sn coils. The Cu–Nb composite material functions as a reinforcing stabilizer during the superconducting magnet operation. Moreover, it suppresses the damage of reacted Nb₃ Sn filaments due to applied stress during the manufacturing process such as the prebending treatment, the insulating, and the winding. New Cu–Nb/Nb₃ Sn wires with high tin bronze (Cu-15.7wt%Sn-0.3wt%Ti) were investigated in the superconducting properties. The round wire of 0.8-mm diameter with prebending strain ε_{p b} = ±0.5% demonstrated a non-Cu-J_c of 1150 A/mm² at 12 T and 4.14 K. The rectangular wire of 1.13 × 1.7 mm with ε_{p b} = ±0.5% applied from both directions of flatwise and edgewise had a non-Cu-J_c of 355 A/mm² at 17 T. In this paper, we discuss the cross-sectional designs of Cu–Nb/Nb₃ Sn wires suitable for practical R&W Nb₃ Sn applications.