The effect of geometry of composite MgB₂/stainless-steel (SS) wires fabricated by PIT process on the superconducting properties

Single-, multi-, and two kinds of coaxial-filament composite MgB ₂/SS-SS (stainless steel for both outer and inner tubes) and MgB ₂/SS-Cu (stainless steel for outer tube and copper for inner tube) wires were successfully fabricated using powder-in-tube (PIT) process with swaging only. The effect of the geometries of the MgB₂ PIT wires has been studied comparatively. The isothermal magnetizations M(H) for both the sintered and the as-rolled single-, multi-, and coaxial-filament MgB₂ wires were measured at temperatures between 5 and 50 K in fields up to 5 T. The critical current density was estimated by the M(H) data using Bean model. The coaxial-filament composite MgB₂ wires showed much better J _c than both the single- and the multi-filament composite ones. The results of this study show that the superconducting properties of the MgB ₂ PIT wires/tapes can improve by employing better geometries such as the coaxial-filament composite MgB₂/SS-SS wires.