Final report SBIR Phase II. High current density (Jc), low A.C . loss, low cost, Internal-Tin Superconductors

Final report of SBIR to develop an economical process that can produce the best material for high field magnets to be used in the next generation of accelerators. The overall objective is to develop an economical process that can produce the best material for high field magnets to be used in future particle accelerators. The internal-tin process has shown by others to produce high Jc Nb3Sn material and the work here is primarily directed to lowering the AC losses, increasing piece lengths and lowering costs. In the previous reports on this Phase II work we have explored the finned restack approach. We have however encountered ductility problems when we have attempted to produce material without fins but with large numbers of subelements in the restacks. The work reported has concentrated on the scale up of the internal-tin materials without fins and we have finally made internal tin material with 40 (micro)m subelements which exhibited a Jc at 12 T of 2757 A/mm2 in the non-Cu and a Jc at 14 T of 1985 A/mm2 in the non-Cu. These results are the best we have achieved to date and are approaching those that Oxford has achieved for sometime.