High Tc Bi2Sr2CaCu2Ox superconducting powder and wires for high field magnets

High field magnets > 16 T) are required for next generation accelerators and upgrading existing facilities. Fields greater than 20T can only be achieved by using the High temperature superconductor [Bi2Sr2CaCu2Ox Bi-2212) and YBa2Cu3Ox] due to their high upper critical field Hc2. Multifilamentary round Bi-2212/Ag wires have demonstrated many attractive features, such as high irreversibility field Birr > 100T), isotropic electromagnetic performance, solenoid layer winding, highest engineering critical current density, JE, at fields higher than 20T and compatibility with conventional cabling and strand insulation methods. These advantages make it easy to adapt the well established Nb3Sn technology and make Bi-2212 one of the most promising materials to enables superconducting magnets > 20 T range. Even though there are encouraging reports on the suitability of Bi-2212/Ag multifilamentary wires, the R&D efforts for high field magnets are focused on low temperature superconductors mostly due to availability in long continuous lengths with uniform properties. Improving the properties and the piece- length of the Bi-2212 superconductors is of highest importance for the growth of these materials as possible conductors in magnets for high energy particle colliders. A reliable source of powder with definable properties is needed for the stabilization of the wire manufacturing process, particularly to avoid the JE limiting defects. Performance of a wire depends upon the interplay between powder characteristics, wire drawing process variables and configuration, and thermal processing of the wire. The proposed Small Business Research Program key challenges for demonstration scale >1km lengths) wire for magnets with field between 25 T to 50T and focuses on improving JE, of round multifilamentary wires, reduce flaws in long length conductors and reduce cost by improving yield. In this program, the powder production will be improved to produce high tap density powder without hard particles. The high density powder has been proved to facilitate wire manufacturability on large billet fabrication and enhance wire uniformity. However, it may lead to shorter piece-length and lower yield if some hard particles are present. We will work with Oxford Superconducting technologies OST) to find the optimum tap density range and establish process control needed to maintain it. Effect of secondary phase additions will also be investigated in an attempt to increase JE and the processing heat treatment window of multifilamentary Bi-2212/Ag wires which is critical for manufacturing long length wires, cables and magnets coils). Powder with optimum tap density will be supplied to OST for fabricating Bi-2212/Ag wires. In parallel effect of secondary phase additions on the melting point and the phase assemblage will be studied in Phase I. Round multifilamentary wires will be produced and tested in Phase II from the selected compositions. Successful completion of the proposed program will enable availability of a reliable commercially viable domestic source of stable powder which is critical for downstream process stabilization of Bi-2212/Ag composite wires for high field magnets.