Neutron irradiation effect on critical current and critical temperature of Nb₃Sn wire

The ITER project is ongoing in France, and it is expected that a lot of high energy neutrons will be generated, and some neutrons will reach to superconducting magnets. To keep the safe and stable operation of the superconducting magnets, the neutron irradiation data must be piled up and the mechanisms of the irradiation effect must be investigated. A 15.5 T superconducting magnet and a variable temperature insert were installed in a radiation control area at Oarai centre in Tohoku University, and the superconducting properties of the irradiated Nb₃Sn wires have been evaluated. The critical current was improved once and drastically dropped after irradiation of 10²³ n/m², and the critical temperature degraded monotonically, and the critical magnetic field decreased around 17 T after the irradiation of 10²³ n/m². The mechanism of the irradiation effect was discussed based on a flux pinning concept.