Investigation of Superconducting Properties of Nb3Sn Strands by Internal Tin Process for ITER

The multifilamentary Nb3Sn strands with a diameter of 0.82 mm and different local area ratios of Nb to copper (LAR) have been successfully fabricated by an internal tin process in Western Superconducting Technologies Co., Ltd. (WST). The heat treatments have been completed in a vacuum condition. The Critical Current (I-c) and hysteresis loss of the strands are measured after different heat treatments according to ITER requirement. The maximum I-c is about 285 A (4.22 K, 12 T, 0.1 mu V/cm) and the hysteresis loss is 290 similar to 410 mJ/cm(3) (4.22 K, +/- 3 T) per strand unit volume. In this paper, the I-c and the hysteresis loss of the strands with different LARs and different heat treatments are investigated. It is a reference for fabricating the qualified Nb3Sn strands for ITER project in large scale in WST.