Division of accelerators, cryogenics and magnetism

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 J_C 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.