Bi-2212 Round Wire Development for High Field Applications

Oxford Superconducting Technology continuously improves Bi-2212 round wire performance because this product has a unique property for ultra high-field magnet (> 25 T) applications. Our recent results on improving the engineering current density by filament densification and reducing trace carbon and hydrogen contamination are presented. The swaging, isostatic pressing, and over-pressure heat treatment processes have been demonstrated to effectively increase the Bi-2212 filament mass density in the final wire and results in high performance over long wire length. Engineering current density values exceeding 550 A/mm(2) at 4.2 K, 15 T have been achieved on 1-m-long barrel samples. Several configurations have been developed to meet different operating current requirements with optimum filament size (similar to 15 micron) on critical current density, J(c). The round wire has also been twisted down to 12 mm in twist pitch length without performance degradation.