On the Optimization of In Situ Nb₃Sn-Cu Wire

Abstract

In this paper we report on two aspects of our efforts to optimize large-scale in situ Nb₃Sn-Cu superconductor wire. First, results will be presented that show that the as-drawn Nb filament size is critical in optimizing J_c values and depends upon the temperature of the Sn diffusion anneal. Second, laboratory-size experiments show that utilizing C containers for ingot preparation results in a small C contamination and significantly lower J_c values. To scale-up the in situ process, we have previously developed arc-casting techniques capable of producing 30-kg ingots utilizing graphite-lined Cu molds. Results are presented here on efforts to reduce C contamination in these large castings by utilizing ceramic coatings on the graphite liner.