An examination of the properties of SSC Phase II R&D strands

The authors summarize a detailed characterization of the Superconducting Super Collider (SSC) Phase II R&D billets, samples of which were supplied to the University of Wisconsin (UW). An important part of the SSC Phase I and II strand R&D programs was an extensive sampling scheme that covered the entire fabrication process of the strand. Samples were sent to UW, where complete microstructural and physical property analysis could be performed. In addition, sufficient extruded pre-heat-treatment multifilamentary material was provided to OW so that parallel processing to strand could be performed. In Phase I material it was found that the 2 vol% Nb diffusion barrier thickness was insufficient to prevent extrinsic limitation of the critical current density (J/sub c/). This contrasted with the Phase II strand which incorporated 4% barriers and showed intrinsic behavior. The intrinsic nature of the Phase II conductor has made it possible to probe the basic microstructure property relationships of the strand and provide insight into improvements in future processing.<>