Development of Nb-Ti-Ta ternary alloy multifilamentary superconducting wire

The superconducting wire with approximately 10 mu m diameter filaments of N b-41wt%Ti-28wt%Ta alloy was fabricated from our standard production billet. Critical current densities and upper critical fields after various heat tr eatments were measured in the temperature range of 4.2 K to 1.6 K. Thermo-m echanical treatments for alpha-Ti precipitates were optimized to improve cr itical current densities. A 27-strand Rutherford type cable having a large keystone angle was trial-fabricated using the optimized-processed wires. Th e achieved J(c)'s were 1383 A/mm(2) (10 T and 1.9 K) and 602 A/mm(2) (12 T and 1.9 K). The Fabricated wire was proved to have high homogeneity and goo d workability.