Superconducting properties of neutron irradiated Nb3Al multifilamentary wires fabricated by the Nb-tube process

The superconducting critical temperature and the critical current of Nb-tube processed Nb3Al multifilamentary wires irradiated at reactor ambient temperature have been measured as a function of neutron (n) fluence up to 1.2 x 10(19)n cm(-2) (E > 0.1 MeV). The critical temperature decreases monotonically with neutron fluence. The neutron fluence dependence of the critical temperature for these Nb3Al wires is found to be basically similar to that for Nb3Al bulk samples. On the other hand, the critical current in magnetic fields of 6 T and 8 T remains almost unchanged up to a fluence of 1.4 x 10(18)n cm(-2) and then rapidly decreases with increasing fluence. This peculiar dependence on neutron fluence of the critical current may be attributed to off-stoichiometric composition and the extremely small size of Nb3Al filaments. The critical currents decrease monotonically with applied tensile strain for both unirradiated and irradiated samples. The rate of decrease in the critical current with samples tends to be smaller than that for unirradiated samples.