In the first and main part of my talk, I will describe the evidences leading to the new heat treatment optimization philosophy based on Cu diffusion in Nb3Sn wires, and some recent results of performance improvement. This idea of following Cu diffusion to optimize Nb3Sn performance was surprising to many in that (1) Cu is not a constituent of Nb3Sn and (2) Cu diffusion occurs at a temperature much lower (i.e. much earlier) than Nb3Sn formation. But I will show how the conventional Sn diffusion perspective cannot explain the subelement core phase development, and how Cu diffusion is related to Nb3Sn grain size and distribution – thereby JC of the wires.
In the second part, I will provide a tour of the Berkeley cabling facility through photos, and highlight our quality control and analysis capabilities.
Finally, I will advertise the extrapolative scaling expression spreadsheet that I built and that is freely available to anyone.
