Development of Nb₃Sn Multi-filamentary Wires Superior in Mass Productivity

Abstract

We have developed superconducting wire about bronze route Nb₃Sn and internal tin processed Nb₃Sn. SH Copper Products Ltd. manufactures bronze route Nb₃Sn superconducting strands for ITER-TF coils under a contract with the Japan Atomic Energy Agency (JAEA). The Nb₃Sn strands which are composed of Nb-1 wt%Ta filaments and Cu-15.5 wt%-0.3 wt%Ti bronze have good workability and high performance. More than 850 A/mm² of non Cu J_c at 12 T can be stably obtained using two-stage heat treatment technique. The internal-tin technique is an excellent method for fabricating Nb₃Sn superconducting wire with a high critical current density. We have developed a new type of internal-tin Nb₃Sn wire in which the multi-filamentary wire is fabricated by combining mono-filamentary Nb elements and mono-filamentary Sn elements. The simple fabrication process will enable the fabrication cost of the wires to be reduced.