Fabrication and Investigation of Nb3Sn Strands by RRP for High Field Magnet

Abstract:

The Nb3Sn strands over 1500 m piece length by Rod Restack Process (RRP) for high field magnet were fabricated by Western Superconducting Technologies Co., Ltd. (WST). The distributing Nb barriers were employed around each sub-element in the process, which not only protect the Cu stabilization from the pollution of Sn, but also contribute to the critical current for forming A15 phase Nb3Sn during the reaction. Meanwhile, Nb-47wt%Ti filaments were adopted to replace some of Nb as the resource of Ti adding in the process, lowering the production price the commercial Nb-47wt%Ti. The testing results show that the Ic of the strands with better stability is 514 A at 12 T, 4.2 K, 0.1 μV/cm with the heat treatment of 640 ℃, 60 h and the RRR value is 148. While the Ic is 599 A with the heat treatment of 665 ℃, 60 h and RRR value is 3.77. The success choosing of barrier and Ti doping make it possible to develop higher quality strands, including long piece length and high critical current