Application of Prebending Effect to Triplet Cables Using Bronze-Route Nb₃ Sn Strands

An application of the prebending effect to a cabling process using Nb3Sn strands was demonstrated. The prebending effect is the enhancement effect of superconducting properties due to the repeated prebending treatment for practical bronze-route Nb3Sn wires. CuNb/Nb3Sn and Cu/Nb3Sn strands were applied prebending treatment using 10 fixed pulleys with 0.8% prebending strain. Four kinds of triplets, i.e., prebent CuNb/Nb3Sn, no-prebent CuNb/Nb3Sn, prebent Cu/Nb3Sn and no-prebent Cu/Nb3Sn triplets were fabricated. Critical currents were measured for the four kinds of triplets in magnetic fields up to 11 T at 4.2 K. The obvious critical current enhancement due to the prebending effect was maintained for the prebent CuNb/Nb3Sn triplet. The results imply that the prebending treatment for high-strength Nb3Sn strands is applicable to the cable conductor fabrication.