Improvement of the Properties of Tubular Internal-Tin Nb3Sn

The development of an economical process that can produce an improved material for high and intermediate field magnets, such as those needed in future accelerators, will require an increase the stability of the strands and cables particularly in the lower fields. This stability can be achieved by reducing defects and improving the residual resistance ratio (RRR) of the material, but it must be done without lowering the critical current carrying capability (Jc) in the high field region, as the fields of interest are 16T and above. A tubular Nb3Sn material surrounded by a matrix with good electrical and thermal conductivity has been suggested as one solution, but this material has a relatively low current carrying capability. Therefore, this project will improve the critical current carrying capability (Jc) of this tubular Nb3Sn, while maintaining low cost and good ductility. Phase I will: (1) make and test a 217 (204+13) restack, where the sub-elements are 33 µm in diameter at a wire diameter of 0.7 mm; (2) improve Jc in the non-Cu as much as possible, while maintaining the deff and RRR; and (3) make one further restack with 270 sub-elements and test it for ¿flux jump¿ stability. In Phase II, the principal objective will be to scale up the process. Commercial Applications and other Benefits as described by the awardee: In addition to being used for high energy physics accelerator applications, the product should be useful for open area MRI (MRI is the largest commercial application of low temperature superconductors), small magnets for high field laboratory applications, and NMR.