Effect of Prebending Strain on rm CuNb/Nb₃rm Sn Superconducting Coils Using a React and Wind Method

We have found that superconducting properties such as a critical current for bronze route Nb3Sn superconducting wires were enhanced by prebending strain (epsivpb), which is the repeated bending strain at room temperature. In this study, four kinds of react and wind (R&W) processed CuNb reinforced bronze route Nb3Sn coils with epsivpb=1.0, 0.8, 0.5 and 0% were prepared. We investigated the effect of prebending strain for the coils. In the electromagnetic compressive stress condition, a critical current (Ic) of the R&W processed coil was enhanced by the prebending strain. These Icvalues are larger than those of a short sample wire without prebending strain. In the hoop stress condition, the Icof four coils revealed a similar value. Therefore, it is considered that the Icwas limited by the large tensile stress for all coils in the hoop stress states. These results suggest that the Icenhanced by the effect of prebending strain is applicable for the R&W coil design without degradation in large stress and strain states