Stable, low-loss joints for HTS fusion magnets

The feasibility of fusion as a practical energy source needs to be improved significantly by removing some of the restrictions that low temperature superconductors put on the fusion magnet systems. One method to simplify the magnet system is by using high temperature superconductors that allow for a higher magnet performance and much larger temperature margins. The larger temperature margins allow for superconducting demountable fusion magnets, which would significantly reduce the magnet construction complexity and maintenance time and costs. There are currently no feasible methods to construct demountable fusion magnets from superconducting cables. This proposal seeks to develop methods to develop low loss joints for use in high temperature superconducting cables, allowing development of demountable superconducting fusion magnets. During Phase I, we will determine the feasibility of making practical and reliable joints in high temperature superconducting cables that carry as much as 5 kA in a background field of 14 T. During Phase II we will further optimize the joint structure such that it can be applied to cables that carry 60 kA in 14 T background field. Reliable low loss joints in high temperature superconducting cables will enable demountable fusion magnets that are less complex to construct and easier to repair and maintain than conventional fusion magnets. Demountable cable joints will directly benefit other applications, such as high energy density, superconducting power transmission on board of Navy vessels, Air Force aircraft and data centers.