Performance of joints in the CS model coil and application to the full size ITER coils

Takahashi, Yoshikazu; Yoshida, Kiyoshi; Mitchell, N.*; Bessette, D.*; Nunoya, Yoshihiko; Matsui, Kunihiro; Koizumi, Norikiyo; Isono, Takaaki; Okuno, Kiyoshi

Cable-in-conduit conductors that consist of about 1,000 NbSn strands with an outer diameter of about 0.8mm, have been designed for the TF and CS coils of the ITER. The rated current of these coils is 40 -68kA. Two joint types (Butt and Lap) were developed during the CS Model Coil project. The performance of these joints was evaluated during the operating tests and the satisfied results were obtained. The joints of the TF coils are located outside of the winding in a region where the magnetic field is about 2.1T, a very low value as compared to the maximum field of 11.8T at the winding. The CS joints are located at the coil outer diameter and embedded within the winding pack due to the lack of the space. The maximum fields at the CS joint and winding are 3.5 and 13T, respectively. For the TF coils and the CS, the joints are cooled in series with the conductor at the outlet. The maximum temperature increase due to the joule heating in the joints is set at 0.15K to limit the heat load on the refrigerator. It is shown that both joint types are applicable to the ITER coils.