Mechanical evaluation of conductors and joints for the Compact Ignition Tokamak (CIT) central solenoid

The central solenoid for the CIT will be the largest bore diameter, 20⁺-Tesla, coil system ever constructed. The stringent design requirements necessitate an integrated conductor and structure. Toward this end, an explosively bonded laminate of Alloy 718/copper/Alloy 718 has been developed, and samples of advanced materials such as aluminum oxide dispersion-strengthened (ODS) copper and CuNb laminated with copper have been tested. Full-scale, explosively bonded Alloy 718/copper/Alloy 718 plates have been obtained from two vendors and tested. The plates consist of 4.76-mm-thick Alloy 718 sheets on each side of 9.53-mm-thick copper. The plate size is about 1778-mm ². Results on fatigue lifetime under simulated operating stresses and temperatures have been obtained and are compared with similar data on ODS copper and laminated CuNb and copper. Ultrasonic testing methods and results for the laminate are given. Several joint options have been considered and evaluated for the different conductors. The types of mechanical joints, the initial selection process, the test results for components using 718/copper/718 laminates and results for bolted and pinned components using the same material are outlined