Superconducting Properties of Nb₃Sn Multifilamentary Wires Fabricated by Internal Tin Process

Abstract

Since the discovery of the “bronze process” for fabrication of multifilamentary A15 superconducting wires, extensive effort has been made on development of large scale production and on the characterization of metallurgical and superconducting properties of these wires.¹ To date, a number of large very high magnetic field (H>10 T) magnets have been constructed using these wires. However, one primary disadvantage of the manufacturing process is that the bronze matrix hardens rapidly with reduction in size such that the wires have to be annealed at ~50% area reduction. In order to avoid this difficulty, a new process, the internaltin process, was developed by Hashimoto et al.² Recently, using the same process, Schwall et al.³ reported very high-current densities [J_c (excluding Cu) ~1200 to 2000 A/mm² at 10 T] in the subelements of Nb₃Sn multifilamentary wires. These values are ~50 to 100% higher than those which are found in conventional Nb₃Sn wires, and it is of great interest to ascertain these values and to perform thorough metallurgical characterization of the wire. We have purchased small amounts of the unreacted multifilamentary wires from Intermagnetics General Corporation (IGC).

Work supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Sciences under Contract No. DE-ACO2-76CH00016.