Development of High Strength Nb₃Sn Wire for a High Field Magnet Nb₃Sn Wire Reinforced with Cu-NbTi Intermetallic Compound

Abstract

Nb₃Sn superconducting wires reinforced with a CuNi-NbTi compound have been developed. The critical current density of the CuNi-NbTi reinforced Nb₃Sn superconducting wire with a is the same as conventional Nb₃Sn wire without reinforcement, but 0.2% proof stress is twofold higher that of the conventional wire. To investigate distribution of Cu, Ni, Nb and Ti in the CuNi-NbTi wire, observation using EPMA (Electron Probe Micro Analyzer) was performed. Based on these developments, an industrial-scale CuNi-NbTi/Nb₃Sn wire was successfully. The critical current density and 0.2% proof stress at room temperature of the industrial-scale wire were greater than 600 A/mm² at 12 T and 350 MPa, respectively. The high-strength Nb₃Sn wires were applied in the manufacture of a cryocooled hybrid magnet and 18 T cryocooled superconducting magnet at Tohoku University.