Some Improved Methods of Introducing Additional Elements into Internal-Tin Nb3Sn

72046-An economical process is needed to produce the best material for high field magnets to used in future accelerators. Previous work has shown that the introduction of additional elements into internal-tin Nb3Sn superconductors can provide a material that meets the targets for critical current density and loss properties. This project will develop improved methods for introducing the additional elements, particularly titanium and tantalum, into internal-tin Nb3Sn, in order to improve the compositional uniformity and reliability, and reduce manufacturing costs, while maintaining the improved properties. In Phase I, a method of introducing titanium into Nb3Sn, by wrapping Nb7.5wt.%Ta rods with Nb47wt.%Ti foils, was demonstrated. An outer wrap of niobium was put around the Nb47wt.%Ti foil, to permit maximum flexibility in the fabrication procedures. Nineteen subelement restacks were successfully made and drawn down to 0.29 mm diameter without breakage. In Phase II, the billet designs made in Phase I will be modified and other methods of introducing additional elements will be tried, on a small scale at first. Then, the most promising designs will be selected, optimized, and scaled up to full sized billets. Commercial Applications and Other Benefits as described by awardee: In addition to being used in HEP accelerator applications, the product should have application to open area MRI, where the patient is more accessible to the surgeon (MRI is the largest commercial application of low temperature superconductors), small magnets for high field laboratory applications and NMR, and levitated transportation projects.