Neutron irradiation effects on critical temperatures of A15-type superconducting composites

For several Nb 3 Sn and V 3 Ga superconducting composites, T c was measured by the inductance method after reactor irradiation and post-irradiation annealing. The neutron irradiated specimens showed marked degradation of T c , for example to 29.1% of T c0 in in-situ Nb 3 Sn at a neutron fluence of 4 × 10 19 neutrons/cm 2 (E > 0.1 MeV ) . After isochronal annealing to 1073 K the T c degradations recovered 84, 89 and 98% for bronze, tape and in-situ Nb 3 Sn, respectively. The recovery stages appeared at about 723 and 1023 K, which correspond to the movement of radiation-induced and equilibrium vacancies, respectively. The recovery in V 3 Ga tape was 97% at 1023 K, of which main stage occur about 773 K. The shape changes of the inductance-temperature curves after neutron irradiation and isochronal annealing suggest effects of cascade damage on the T c degradation.