Technology development and mass production of NbSn conductors for ITER toroidal field coils in Japan

Takahashi, Yoshikazu; Isono, Takaaki; Hamada, Kazuya; Nunoya, Yoshihiko; Nabara, Yoshihiro; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; Uno, Yasuhiro; Tsutsumi, Fumiaki; Yoshikawa, Masatoshi*; Nakajima, Hideo; Okuno, Kiyoshi; Devred, A.*; Mitchell, N.*

Japan Atomic Energy Agency is procuring the NbSn superconductors for Toroidal Field (TF) Coils under the ITER project. Because manufacturing amount of NbSn strands is quite large compared with the past experience and required superconducting performance is higher than that of the model coils which have been fabricated and tested in the ITER-EDA, quality control technique is very important for the manufacture of the strands. Sophisticated control technique is also required for the jacketing, in order to fabricate the conductors with the precise outer diameter and without leakage at welding part. This paper summarizes the technical developments leading to the first successful mass production of ITER TF conductors.