The Prebending Strain Effect on Nb Sn

The prebending strain effect is that the repeated bending load at room temperature enhances superconducting properties of practical Nb Sn wires. The authors are now inves- tigating the application of the effect to practical superconducting cabling conductors for high field superconducting magnets. Large current capacity and high strength are required for supercon- ducting cabling conductors to make large scale and high field magnets. The superconducting cabling conductor with high strength Nb Sn wires will be useful for making high field magnets. The prebending strain effect was applied to a cabling technique with Nb Sn wires. High strength Nb Sn wires reinforced with CuNb composite and conventional Nb Sn wires without reinforce- ment were prepared, which were heat-treated at 943 K for 345.6 ks. Both wires were bent by 10 pulleys to give 0.8% prebending strain. After the prebending treatment the wires were assembled and fabricated 3-strand cables and 7-strand cables. The cables with high strength Nb Sn wires showed the enhancement of critical currents even after the cabling process. The results imply that the prebending treatment is applicable to the fabrication of cabling conductors for making a high field superconducting magnet.