Development of the NbAl D-shaped coil fabricated by react-and-wind method for JT-60 superconducting Tokamak

Kizu, Kaname; Miura, Yushi; Tsuchiya, Katsuhiko; Koizumi, Norikiyo; Matsui, Kunihiro; Ando, Toshinari*; Hamada, Kazuya; Hara, Eiji*; Imahashi, Koichi*; Ishida, Shinichi; Isono, Takaaki; Kawano, Katsumi; Kawabe, Masaru*; Kawasaki, Tsutomu*; Kubo, Hiroatsu*; Matsukawa, Makoto; Nabara, Yoshihiro; Nunoya, Yoshihiko; Okuno, Kiyoshi; Otsu, Kiichi*; Oshikiri, Masayuki*; Sakasai, Akira; Seki, Shuichi*; Takano, Katsutoshi*; Tsutsumi, Fumiaki*; Uno, Yasuhiro*

Toroidal field coils (TFC) of the JT-60SC consist of 18 D-shape coils. The maximum magnetic field is 7.4 T at an operational current of 19.4 kA. An advanced NbAl superconductor was developed for the TFC conductor material in JAERI. The NbAl has lower strain sensitivity on superconducting performances, and allows us to fabricate the TFC by react-and-wind (R&W) method that makes that the coil fabrication with high reliability becomes easier and the fabrication cost becomes lower. To demonstrate the coil fabrication by R&W method, a two-turn D-shape coil was developed. The D-shape coil was tested at 4.3-4.4K and 7-12T. Measured critical current (Ic) was 30 kA at 7.3 T and 4.4 K. Using the measured conductor and strand Ic values, the strain of the conductor was estimated to be -0.6%. The Ic-B-T characteristic expected by an empirical equation substituting this strain shows that the required temperature margin for TFC is satisfied. Thus, the R&W method was demonstrated to be the applicable fabrication method of the TFC.