We have found that superconducting properties such as a critical current for bronze route Nb3Sn superconducting wires were enhanced by prebending strain (εpb), 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 εpb = 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 Ic values are larger than those of a short sample wire without prebending strain. In the hoop stress condition, the Ic of four coils revealed a similar value. Therefore, it is considered that the Ic was limited by the large tensile stress for all coils in the hoop stress states. These results suggest that the Ic enhanced by the effect of prebending strain is applicable for the R&W coil design without degradation in large stress and strain states.
- Critical current
- Prebending strain
- React and wind processed coils