Lower Cost Nb3Sn Internal-Tin Strand for ITER Fusion Project

75980-Lower cost Nb3Sn superconductors are required for such fusion projects as the International Tokamak Experimental Reactor. This could be achieved by reducing the percentage of Nb in each strand; however, the challenge is to assure that the strand still can meet the high current density specification for ITER. This project will demonstrate a Nb3Sn strand can meet the ITER specification with 60 percent less Nb compared to state-of-the-art, internal Sn, Nb3Sn ITER superconductors. In addition, a technique will be demonstrated for increasing the piece length by up to a factor of four for a given restack billet size, thereby dramatically lowering the cost for an ITER-specification strand. Phase I will fabricate high current density sub-elements, restack the sub-elements into several different configurations, and demonstrate that these configurations meet the ITER superconductor strand specification. Properties of the final strand will be tested for both magnetic and transport Jc, as well as for AC losses. Commercial Applications and Other Benefits as described by the awardee: The technology should lead to dramatically lower costs for the conductor and, therefore, significantly lower costs for the entire ITER fusion project. In addition to the application to fusion magnets, the high field magnets (above 5 tesla) should find use in MRI, NMR, high gradient magnetic separators, and SMES applications.