A Ta Doped ITT Type Nb3Sn Conductor with Improved Fabrication Characteristics

The internal tin tube (ITT) process is potentially the lowest cost approach for manufacturing Nb3Sn superconductors. A present, multifilament conductors made by the ITT process are of necessity cold processed to wire. Since the filaments are not metallurgically bonded to each other, they can move relative to one another during wire drawing. To maximize high field performance, the conductor is made from an Nb-7.5Ta alloy. The high strength of this alloy increases the difficulty in cold processing the wire. The result is a high incidence of filament defects causing wire breakage, which limits product yield and increases the cost of the conductor. This proposal investigates a new method for fabricating ITT Nb3Sn superconductor that could eliminate the difficulty in producing this material, while making it more cost effective. Copper clad Nb-7.5Ta tubes will be fabricated via tube extrusion and drawing. The drawn tubes will be tightly bundled to form a restack array and vacuum annealed at ~1000 C to diffusion bond the subelements. When the subelements in the wire are metallurgically bonded, the wire can be more cost-effectively processed and the risk of wire breakage is reduced. Commercial applications and other benefits: Multifilamentary Nb3Sn has its major application in high energy physics particle accelerators and magnetic confinement fusion machines. These machines are very expensive to build and operate, and must be run at maximum performance to be effective. Reducing the cost and increasing the reliability of the superconductor strand used to fabricate the magnets for these machines will lower their overall cost. Additionally, a lower cost Nb3Sn superconductor resulting from improve manufacturing would benefit the manufacture of high field NMR magnets which are used for exploration of new molecules and chemical compounds for advanced materials and biological and pharmaceutical applications.