Advanced MgB2 wire made by internal magnesium diffusion process

Single- and four-core MgB2 wires have been manufactured by internal magnesium diffusion (IMD) into boron. Longitudinal uniformity of the composite wires has been checked by X-ray micro-tomography measuring the MgB2 cross section area along the wires length. High density of MgB2 was evaluated by micro-hardness measurements. It was found that the filament's density has a direct effect on the critical current density (Jc). The highest Jc was measured for the wire having the boron core densified by cold isostatic pressing with 1.9 GPa applied prior to final heat treatment. Presented results showed that high current density can be reached in MgB2 wires obtained by IMD, which are very interesting for the future practical applications of MgB2 superconductors.