Development of round multifilament Bi-2212/Ag wires for high field magnet applications

Bi-2212/Ag conductor is one of the most promising materials for expanding superconducting magnet applications to higher fields and/or temperatures than present LTS systems. From the view point of practical application, Bi-2212 round wires have significant advantages over more typical HTS tape conductors, such as no anisotropy, ease of handling and simpler coil winding, allowing considerable flexibility in the magnet design. Development efforts at OST have been aimed at enhancing transport properties in long length round wires for high field magnet applications. Recently, significant improvements in the J_E and J_c performance have been achieved by optimizing the starting powders, the filament size and fill factor, the deformation processes, and the melt-solidification parameters. The highest J_E of 266 A/mm² and J_c of 950 A/mm² at 4.2 K, 45 T with n-value of 17 was obtained in 0.81 mm wire. In this paper progress on the development of Bi-2212 round wires will be reported.