Superconducting currents of scarf joints between single-core <i>ex situ</i> MgB₂ wires

Abstract Superconducting joints between single-core MgB 2 /Fe wires made using an ex situ powder-in-tube process were manufactured using a scarf joint architecture. MgB 2 powders of variable particles and different deforming ratios were applied to a set of joints that were finally annealed at 950 °C/30 min. The critical transport currents of the joints were measured at 4.2 K and external magnetic fields up to 6 T and compared with the currents of unjoined MgB 2 /Fe wires. The structure of the joint interfaces was analyzed by optical microscopy. The joint transport current is dominantly affected by the applied deformation by pressing, which is optimally ∼20%. It was also found that the addition of finer MgB 2 powder between the joined wires allows the creation of better connected superconducting current paths. The presented results show that the scarf joint architecture is a simple process, which could possibly be used for the fabrication of superconducting joints of MgB 2 coils working in persistent mode.