Neutron Irradiation of SiC Doped and Magnesium Rich MgB$_{2}$ Wires

Monofilamentary SiC doped wires and multifilamentary wires made from magnesium-rich powders were exposed to thermal neutrons. The induced defects enhance the field, up to which the resistivity is zero ("irreversibility field") at 4.2 K (by about 1-2 T), and, therefore, reduce the field dependence of the critical current density. On the other hand, the transition temperature decreases from about 35 K to 32.5 K, thus restricting the beneficial effect of neutron irradiation to low temperatures. Changes of the critical current density are discussed in terms of changes of the fundamental superconducting parameters (condensation energy, upper critical field, anisotropy) and changes of the flux pinning properties.