High field magnets (>16 T) are required for next generation accelerators and upgrading existing facilities. Fields greater than 20T can only be achieved using the High temperature superconductors [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 to make Bi-2212 one of the most promising materials to enable superconducting magnets in the > 20 T range. Even though encouraging reports exist 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 greater use 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 will address key challenges for demonstration scale (>1km lengths) wire for magnets with fields between 25 T to 50T, as well as for production scale (> 3 km) in fields between 16 to 25 T. The SBIR also focuses on improving the JE, of round multifilamentary wires, reduce flaws in long length conductors and reduce cost by improving yield. In this program, powder production will be further optimized to facilitate wire manufacturability on large billet fabrication and enhance wire uniformity. The composition of the powder will be addressed by adding fine secondary phases (<100 nm) 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). Powders made by MetaMateria will be supplied to B-OST for fabricating Bi-2212/Ag wires with diameter 0.8-1.2 mm. This team has already demonstrated JE ~ 530 A/mm2 at 15 T on 1 mm diameter wire. The affect of secondary phase additions on the melting point and the phase assemblage will be studied. During Phase I short length wires will be fabricated. Long length (<1 km) round multifilamentary wires will be produced and tested in Phase II from the selected compositions. Commercial Applications and Other
Benefits: Successful completion of the proposed program will enable availability of a reliable, commercially viable domestic source of stable powder that is critical for downstream process stabilization of long Bi-2212/Ag composite wires. Availability of commercial scale cost effective round Bi-2212/Ag is critical for developing high field magnets for next generation accelerators and high field (~30 T) NMR.
