Critical current density and superconducting parameters Tc, Hc2, and k in neutron-irradiated and annealed V3Si

Single and polycrystalline V3Si was neutron irradiated at 240°C up to a fluence of 1.2 × 10¹⁹cm^-2and subsequently isochronally annealed up to 1330°C. Measurements include the critical current density, jc, the critical temperature, Tc, the upper critical field, Hc2, and the residual resistance. Dislocation loops are identified by TEM as the part of the radiation induced defects responsible for jc. Two different annealing temperatures are found for Tcand jc, respectively. Due to the high irradiation temperature, Tcrecovery occurs in one stage only, corresponding to thermally produced vacancles. All samples exhibit a scaling behavior of the volume pinning force between 0.9 and 0.6 reduced temperature. A jc(H) peak is observed at low fluences and high annealing temperatures. The explanation for this behavior is based on a concentration dependent reduction of the theoretical threshold. A saturation behavior of the volume plnning force for high fluences and low annealing temperatures is observed, which is in quantitative agreement with the high-field mechanism of Kramers model above 0.8 reduced field. With these results we can explain the field dependent enhancement of jcafter neutron irradiation of A15 superconductors with grain boundary pinning.