The effects of neutron irradiation damage on the superconducting properties of Nb3Sn

Specimens of Nb₃Sn have been irradiated by fast neutrons at 70°C to doses in the range 3 × 10²¹ neutrons m^?2 to 9 × 10²³ neutrons m^?2. Their critical temperatures were depressed linearly with dose, to less than 4.2 K after about 3 × 10²³ neutrons m^?2. The critical temperature recovered to their initial values in anneals of 2 hours at 900°C, and in 64 hours at 750°C.The critical current can be enhanced by low neutron doses, particularly at high fields, but is always depressed by higher doses.The observations are shown to be consistent with a qualitative model, and in the light of this the likely consequences of irradiation at operating temperature are considered.