High Field Nb3Sn Superconductor Fabricated by the Internal‐Tin‐Tube Process

Multifilament Nb3Sn superconductor has been produced by the internal‐tin‐tube approach. In this method tubular niobium filaments containing either solid or powder cores of high tin content are processed into multifilament conductors containing filament diameters as small as 30 μm. The recent emphasis has been on incorporating Nb‐7.5Ta filaments in an effort to raise the upper critical field and hence increase the critical current density. Comparison to recent results with our powder‐in‐tube A15 conductor is made. Niobium‐tantalum tube fabrication, wire processing, filament quality and Nb3Sn microstructure are discussed and the superconducting properties are presented.