Nb3Sn multi-filamentary superconducting wires prepared by Ta-Sn powder in tube process

Nb₃Sn multi-filamentary superconducting wires prepared by Ta-Sn powder in tube (TS-PIT) process have been developed. To develop the TS-PIT wire with applicable scale, a two stage approach was examined. At the first stage, two kinds of test wires with single and 19 filaments were fabricated by using 10 kg class billets. The critical current density (Jc) of the single filament wire was 167 A/mm² at 21 T and 4.2 K. Based on results of the first stage developments 50 kg class scale wire with 54 filaments was progressed in the following stage. This wire showed Jc of 136 A/mm² at 21 T, 4.2 K. Beside Jc, RRR and 0.2% yield strength were estimated. From these estimations, it was clear that the wire in the second stage has efficient applicable properties to the high field magnet. In both stage, microscopic analysis were followed for samples and found that over 50% in the sheath area reacted uniformly and the grain size was extremely fine. Through this development, TS-PIT processed multi-filament Nb₃Sn superconducting wire has been developed to applicable quality and scale.