Study on the NbTi/Cu30Ni Superconducting Switch Wire Recently in WST

Abstract

The superconducting switch wire is a key component in the superconducting magnet. If the superconducting magnet quenches during the operation, the switch will disconnect automatically and avoid the magnet to be damaged. The Cu-30 wt.% Ni alloy was used as matrix to manufacture superconducting switch wires because of its high resistance characteristic. However, because of its high hardness and work hardening characteristics, the risk of wire breakage occurred easily in the cold drawing process. Therefore, the way to solve this problem is one of the difficulties in the preparation of the superconducting switch wire. NbTi/Cu30Ni superconducting switch wires with filaments number of 55 were designed and fabricated by double stacking method, hot extrusion, cold drawing and heat treatment. Then, the NbTi/Cu30Ni superconducting switch wires with the diameter of 0.500 mm, the Cu30Ni/SC of 1.1, and the maximum length of 40.68 km were obtained. Finally, the six insulated NbTi/Cu30Ni wires and one insulated Cu core wire were cabled to the final cable with the diameter of 1.700 mm and the twist pitch of 36 mm. WST has already achieved mass production of NbTi/Cu30Ni superconducting switch wire. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> at 5 T & 4.2 K of the wire is 280.7 A and the line resistance is 2352 mΩ/m. At present, the Western Superconducting Technologies Co., Ltd (WST) superconducting switch wires and cables have been successfully delivered to many different Chinese superconducting magnet manufactures and received good reviews and feedback.