Cost-Reduction Techniques for Powder-in-Tube Niobium-Tin Superconductors

60746 Nb3Sn superconductor, produced by the powder-in-tube (PIT) method has shown excellent critical density and strain tolerance. Based on performance alone, PIT-type conductors would be utilized in many high field magnet applications including high energy physics. However, the high cost of production has limited widespread adoption of this promising conductor. This project will develop cost reduction techniques for the production of PIT Nb3Sn superconductors. This includes reducing the cost of the NbSn2 powder by new manufacturing techniques, producing Nb tubes by hot extrusion resulting in uniform composite tubes, and using hydrostatic extrusion for multifilamentary billets. In Phase I, a single step reaction heat treatment was developed to produce uniform, homogenous NbSn2 powder (<5¿m). Nb tubes were manufactured by both tube extrusion and salt core extrusion. A multifilamentary PIT wire was constructed and drawn such that the filament diameter reached 100 um diameter. Samples were heat treated under a range of conditions and then tested for critical current density. In Phase II, the processes will be scaled up to larger qualities so that yields can be further increased and costs reduced for producing the NbSn2 powder. A novel chemical synthesis approach to NbSn2 production will be investigated. Composite Nb tubes will be produced in larger sizes for use in the scale up attempt. Hydrostatic extrusions will be attempted in order to produce multifilamentary wires. Commercial Applications and Other Benefits as described by the awardee: High performance, low cost multifilamentary Nb3Sn should find applications in high energy physics particle accelerators and fusion machines. Commercially, the conductor should find application in high field Nuclear Magnetic Resonance magnets and in cyrocooled MRI magnets to take advantage of the high critical temperature of Nb3Sn