Fabrication and installation of equilibrium field coils for the JT-60SA

Tsuchiya, Katsuhiko; Kizu, Kaname; Murakami, Haruyuki; Kashiwa, Yoshitoshi; Yoshizawa, Norio; Yoshida, Kiyoshi; Hasegawa, Mitsuru*; Kuno, Kazuo*; Nomoto, Kazuhiro*; Horii, Hiroyuki*

The programme of constructing JT-60SA device is progressing under the framework of the Broader Approach project. Superconducting poloidal field (PF) coil system, which was decided to be procured by Japan, consists of a central solenoid (CS) with four solenoid modules and six equilibrium field (EF) coils. Each of EF coil has individual diameters, 4.5 to 12 m. Fabrication of EF4 coil, which is set at the lowermost of torus, was started from the beginning of 2009 as a first EF coil. EF4 coil has ten double pancake (DP) coils, and sizes of circularity were measured for all DP coil after curing process. Maximum error of circularity was 3.1 mm, which was nearly a half of the design tolerance, 6 mm. After stacking these DP coils, winding pack of EF4 was completed in the spring of 2012. After optimizing the positions of DP coils to cancel the error of circulation which each DP coil has, error of radial current centre of DP coils will be achieved in the range between + 0.2 to - 0.4 mm. Structural analysis of terminal structure was also performed. Terminal part has a pair of conductors bended toward the lower side of winding pack. A side of them (positive terminal) was covered by stainless steel armor to prevent the movement by electromagnetic force because a length of conductor was longer due to starting from the top of winding pack. Another side (negative terminal) was not covered by armor in the first design because this length was relatively short. However, it was clear on the structural analysis that mechanical strength of insulation around this terminal was not sufficient. Therefore, we also reinforced this side with stainless steel. From this April, fabrication of EF coils with large bore (larger than 8 m of diameter) will be started at the facility built in JAEA Naka site. In this paper, we will discuss about technological problem during the fabrication of large bore EF coils, such as temperature control at the winding process.