Critical currents,<i>I</i>_c-anisotropy and stress tolerance of MgB₂wires made by internal magnesium diffusion

Abstract

Single- and four-core MgB2 wires have been manufactured by internal magnesium diffusion (IMD) into boron. Initial hydrostatic extrusion was applied for single-core Cu sheathed wire and mostly rolling deformation for assembled four-core wires with Inconel or GlidCop sheath. The highest critical current density (Jc) was measured for the wire with boron densified by cold isostatic pressing by 1.9 GPa. Rolled tapes have exhibited critical current anisotropy increasing with the tape's aspect ratio. Low critical current degradation of IMD wires by twisting has been observed, which can be utilized for effective reduction of AC losses. High engineering current densities of IMD wires are promising for the generation of magnetic fields between 1 and 3 T at cryogen-free conditions, which can be utilized for future MRI systems or wind power generators.