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

Cable-in-conduit conductors (CICC) consisting of about 1000 Nb₃Sn strands with an outer diameter of about 0.8 mm, have been designed for the TF and CS coils of the ITER. The rated currents of these coils are 68 and 40 kA, respectively. 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 satisfactory results were obtained. The joints of the TF coils are located outside of the winding in a region where the magnetic field is about 2.1 T, a very low value as compared to the maximum field of 11.8 T at the winding. The CS joints are located at the coil outer diameter and embedded within the winding pack to minimize the space occupied around the coil. The maximum fields at the CS joint and winding are 3.5 and 13 T, respectively. For the TF coils and the CS, the joints are cooled in series with the conductor at the outlet. The maximum allowable temperature increase due to the joule heating in the joints is 0.15K to reduce the heat load on the refrigerator. The stability of these joints at the ITER operating condition was analyzed by using the experimental data. The analysis shows that both joint types are applicable to the full size ITER coils.