ITT Nb3Sn processing and properties

Multifilament Nb₃Sn superconductor has been produced by the internal-tin-tube (ITT) approach. In this approach, tubular niobium filaments containing either solid or powder cores of high tin content (e.g., greater than or equal to 90 percent tin) are processed into multifilament conductors containing filament diameters as small as 30 micrometers. The ultimate goal is to maximize noncopper critical current density while minimizing noncontributing conductor volume. The emphasis to date has been on wire fabrication rather than property optimization. Comparison to recent progress in our powder-in-tube A15 conductor is made. Niobium tube fabrication, wire processing, filament quality and Nb₃Sn microstructure are discussed, and the superconducting properties are presented.