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. Icvalues 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.