Development of Nb-Rod-Method Cu–Nb Reinforced Nb3Sn Rutherford Cables for React-and-Wind Processed Wide-Bore High Magnetic Field Coils

We developed Cu-Nb reinforced Nb₃Sn Rutherford cables for wide-bore high magnetic field coils that were able to be produced by React-and-Wind technique. The Cu-Nb/Nb₃Sn strands were reinforced by internal Cu-20 vol%Nb composites fabricated by the Nb-rod-method and were manufactured through the bronze-process. The Rutherford cables composed of sixteen un-reacted Cu-Nb/Nb₃Sn strands of 0.8-mm diameter were heat-treated at 670 °C for 96 hours. After that, repeated bending strains (pre-bending strains) were applied to the flatwise direction of the reacted Nb₃Sn Rutherford cables at room temperature. Critical current (Ic) values of Cu-Nb/Nb₃Sn strands extracted from the Rutherford cables were compared to those of the single strands that had undergone the same processing as the cables. I_c values under the applied tensile stress of the Rutherford cable were increased by the pre-bending treatment as similar to the single strand. The performances of Cu-Nb/Nb₃Sn Rutherford cables were improved by utilization of the pre-bending process.