Enhancement of Upper Critical Field and Critical Temperature by Prebending Process for Practical Nb3Sn Wires

Abstract

It is recognized that the strain in Nb3Sn conductors is a serious problem, because it suppresses superconducting properties. We have proposed that prebending treatment, which means repeated bending loads, is one of the ways to control the strain state. The upper critical field and the critical temperature were examined for the prebent Nb3Sn wires. We found that the enhancement of the upper critical field from 23.7 T to 25.2 T at 4.5 K and the enhancement of the critical temperature from 17.4 K to 17.9 K were achieved for the CuNb-reinforced Nb3Sn wire by applying the prebending strain. Since these values are similar to those of the strain-free Nb3Sn bulk, the strain state of the wires is definitely optimized by the prebending treatment.