High Performance Nb3Sn Conductor Fabricated by the Internal Tin Tube Method with NbTi Island Doping to Assist in Filament Reaction

The high energy physics community seeks high performance multifilament superconducting wire for use in magnets operating in the range of 12-16 T or higher. Nb3Sn conductors fabricated by the internal tin (IT) method presently represent the state-of-the-art for these applications. However, one problem with ITT conductors is that it is difficult to fully react the niobium in the tubular filaments due to their hexagonal shape, which translates into unrealized non-copper critical current density. In related work, it has been observed that niobium titanium "islands" within the niobium filament annulus of ITT conductors cause an acceleration of Nb3Sn formation in the vicinity of the island sites. This project seeks to take advantage of this effect by placing NbTi island sites near the points of hexagonal ITT-type filaments, in order to achieve a more complete filament reaction without resort to aggressive and potentially detrimental heat treatments. Commercial Applications and other Benefits as described by the awardee: High performance multifilamentary Nb3Sn should find application in high energy physics particle accelerators and magnetic confinement fusion machines. Commercially, the conductor should find application in high frequency NMR magnets ¿ the higher critical current density would enable reductions in the size and cost of the magnet system.