Strong, round cross-sectioned high current density 2212 wire

First commercial High Temperature Superconductors (HTS) are all tape shaped (widths > 10 times thickness), because achieving useful current densities required them to be processed into tape form, even though this also makes it more problematic to use them in some important coil types, for example in ramped and ac field modes; compact, high uniformity solenoid coils; and in large coils where low inductance must be achieved via high current, cabled windings. Our product is the first HTS in commercially usable wire forms that can also be cabled into low loss coil windings. It is based on the 2212 (Bi2Sr2CaCu2O8) HTS material. We have established that among HTS options, only 2212 can be processed to attain useful current densities in wire forms similar to LTS, while surpassing LTS in field generating and operating temperature capability. We have also determined that 2212 is the only HTS that can be 1) cabled into low loss, high current configurations that are required for many ac and ramped field applications, 2) produced with the superconducting joints that are vital for many applications, and 3) scaled up and produced at lower cost than HTS tapes. During the Phase I award period, we developed a test bed and used it to prove the feasibility of manufacturing strong round Bi2212 wire, including equipment and techniques to pre-form the strips to the diameter of the 2212 wire core, payoffs, strip wrapping onto the wire, and diffusion bonding of the strips to the wire. In a series of tests, we demonstrated that these wires are strengthened as required, capable of being bent to small diameters, carry the same currents as unreinforced wires, and can also be cabled such that the cabled wires carry similar currents as un-cabled wires. Our objective continues in Phase II to be develop strong round 2212 wires that are similar in form to proven commercial Nb3Sn round wires, and that, by virtue of their forms, low losses, and superior current densities in very high magnetic fields, offer advantages over present commercial HTS tapes, MgB2 wires and LTS wires in a number of important magnet systems. In Phase II, long length production capability for producing strong, round, high Je, multifilament Bi2212 wire, as well as a representative low loss current cable, will be established (> 100 m wires and > 50 m long cables). Both wire and cable design will also be advanced to enable the design and fabrication of Bi2212-based HTS wires and cables to a wide range of operating current levels, tensile stress / load tolerances, and ramped / ac operation as well as persistent current modes. The suitability of these wire and cables for use in a variety of coils will also be demonstrated by the fabrication and testing of representative solenoid and racetrack coils.