Development of Nb3Sn strands for the International Thermonuclear Experimental Reactor (ITER) in Japan

Development programs focusing on Nb3Sn strands for the International Thermonuclear Experimental Reactor (ITER) are being performed by each party of the ITER group. The object of development is not only to achieve high superconductor performance such as high current density and low hysteresis loss but also enable reliable low-cost mass production, one way of which is to reduce strand breaking during the manufacturing process, and long-length strand fabrication. In Japan, the Japan Atomic Energy Research Institute (JAERI) is involved in this program backed by strong collaboration with many domestic industries. Totally, 11.1 tons (2,400 km-length) of strands that meet ITER specifications have been fabricated successfully. Through this development work, the Nb3Sn strand mass-production technique in Japan has been substantially improved. (author)