Final Report SBIR Phase I, Improvement of Properties of Tubular Internal-Tin Nb3Sn

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 problem is to develop an economical process that can produce material with good properties for high field magnets to be used in the future for High Energy Physics (HEP) applications. The Internal-tin (IT) process, called by some the Restacked Rod process (RRP), for making Nb3Sn has been very successful in achieving high Jc properties in the high field region. As a result it has been used effectively in several high field magnets. Originally, when this material was processed to give the highest Jc it behaved unstably in the low field region and consequently did not perform as well in magnets designed for intermediate field applications. In this field range, the Powder-in-Tube (PIT) material, that has a lower deff and a high RRR, behaved more reliably. The IT material has been improved to give better stability in the low field range and consequently the process offers a considerable challenge to the PIT process for application in both types of magnets. The PIT material has two principal drawbacks - lower Jc and high cost. Work has been carried out to address these two problems and Supergenics I LLC has reported, on a low cost tubular process that is under development. It has fewer problems than the (IT) process in making low deff materials and is of lower cost than both the IT and PIT processes. At the present stage, the Jc's that have been achieved are similar to those of the PIT material but are below those of the IT material. The purpose of the work proposed here is to improve the properties of the material made by this tubular process that has been described previously.