Final Design of the Current Feeders and Coil Terminal Boxes for JT-60SA

The final design of coil terminal boxes (CTBs) and superconducting feeders for the superconducting magnets of JT-60 super advanced (JT-60SA), which is the tokamak device being built in Japan, have been fixed. Because of the limited space in the torus building, five CTBs are distributed around the main cryostat. The CTBs have long horizontal ducts to place the high temperature superconductor current leads in a low magnetic field area. It is required for feeders that both flexibility for deformation of 30 mm, and stiffness for acceleration due to an earthquake of 3.92 m/s
²
(+self-weight of 9.8 m/s
²
) vertically and 5.88 m/s
²
horizontally have to be guaranteed. The design of feeder shape and support structure have been optimized and confirmed by finite-element analysis to satisfy the above requirements. As for the feeder joint, compact tools are required because of the small working space in the horizontal duct of CTBs. Joint resistances were measured to verify the connection tools and procedure. Test results show that the joint resistance meets the requirement of 5 nΩ. In this paper, the final design of CTBs and in-cryostat current feeders for JT-60SA are described and the results of validation tests and analysis are also reported.