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 ( ~ 15 micron) on critical current density, Jc. The round wire has also been twisted down to 12 mm in twist pitch length without performance degradation.