Internal-Tin Nb/Sn Strand with Enhanced Ti Additions Aimed at 17 T Optimization

79663S The DOE High Energy Physics program seeks improved superconductors for high energy particle accelerator applications. Some of these applications will require operating magnetic fields of or in excess of 16 T; however, the selection of the proper level of Ti and Ta additions for Nb3Sn optimization for 16 T class operations has not received much attention. Earlier strand optimizations were targeted at lower fields (e.g. 12 T), where Ti additions were less efficient than Ta at increasing the critical current density (Jc). This project will investigate and optimize the levels of Ti and Ta in NbSn superconductors for optimum 4.2 K, 15-17T operation. In Phase I, two extrusion billets will be fabricated. After strand fabrication, wire samples will be heat treated and tested for Jc at (4K, 12-17 T). The completeness of the reaction heat treatment and the chemistry of the subelements and strands will be investigated by using electron microscopy in conjunction with energy and wavelength dispersive spectroscopy. The residual resistivity ratio, stability, and AC losses of selected strands will be evaluated. Commercial Applications and Other Benefits as described by the awardee: The largest market for the technology will be for accelerator and fusion magnets. Superconducting high field magnets also are used for MRI, NMR, high gradient magnetic separators, and SMES applications.