Cyclic internal pressure tests of a force-cooled cable-in-conduit superconductor for a fusion application

Preliminary results on cyclic internal-pressure tests of a force-cooled, cable-in-conduit superconductor are presented. The tests were performed to assess the effects of initial crack configurations on the final failure modes. Three failure modes have been examined, namely break, leakage, and plastic collapse. Analyses have also been performed on crack propagation to understand the experimental results. Mechanical integrity of the conductor is discussed in terms of a two-parameter method. The experimental and analytical results indicate that plastic collapse or large local plastic deformation should be considered during the design of a conduit. The results also imply that a conduit having square cross section with functional separation of helium sealing and mechanically reinforcing subassemblies is promising for use in a large magnetic system.