Development of the Butt Joint for the ITER Central Solenoid

The ITER central solenoid (CS) requires compact and reliable joints for its cable-in-conduit conductor (CICC). The baseline design is a diffusion bonded butt joint. In such a joint the mating cables are compacted to a very low void fraction in a copper sleeve and then heat treated. After the heat treatment the ends are cut, polished and aligned against each other and then diffusion bonded under high compression in a vacuum chamber at 750 C. The jacket is then welded on the conductor to complete the joint, which remarkably does not require more room than a regular conductor. This joint design is based on a proven concept developed for the ITER CS model coil that was successfully tested in the previous R&D phase.