Improvement of critical current density of bronze processed Nb3Sn superconducting wire

Effects of tantalum addition to niobium filaments and tin contents in bronze matrix on the critical current density (Jc) of Nb3Sn superconducting wires manufactured by the bronze process were investigated in order to improve the Jc in the high magnetic fields. In the results using the bronze composition of Cu-13wt.%Sn-0.3wt.%Ti, the Jc shows a peak for 1 wt.% of tantalum content in the niobium filament. On the other hand, Jc of samples with Cu-14wt.%Sn-0.3wt.%Ti is almost 1.7 times higher than that with Cu-13wt.%Sn-0.3wt.%Ti. From these findings, the authors manufactured a multifilamentary prototype (Nb,Ti,Ta)3Sn conductor made of Nb-1.0wt.%Ta and Cu-14wt.%Sn.0.3wt.%Ti. The non Cu Jc of the conductor was 701 A/mm2 at 12 T and 51 A/mm2 at 21 T for the heat treatment temperature of 650 degrees C