Thermally activated creep and radiation hardness of MgB2 bulk material

In this paper we investigate the effects of ion irradiation on the superconducting properties of polycrystalline high-density MgB₂. We show that the investigated samples are quite radiation hard, both for what concerns the main reference superconducting parameters and, more important, for what concerns the details of the basic vortex dynamics. This property makes magnesium diboride a good candidate for applications in outspace and in harsh environments. The focus of the analysis is on the flux creep phenomena, studied by ac susceptibility measurements at different frequencies and applied fields. The employed analysis method allows obtaining the activation energy as a function of temperature, field and current density, in their full ranges. As a result, vortex-phase diagrams for the unirradiated and the irradiated samples can be compared and discussed.