Fast neutron irradiation effect on superconducting properties of Nb3Sn and Nb3Al strands.

To investigate neutron irradiation effects on superconducting properties, fast neutron irradiation tests of Nb3Sn and Nb3Al strands were carried out using 14 MeV neutron source and fission reactors. Neutron fluence of 2.65×1021 n/m2 was achieved at 14 Mev neutron facility and it was clarified that the critical current in the lower magnetic field increased significantly whereas it did not change in the higher magnetic field, and that the critical temperature decreased by 0.2 K and the critical magnetic field did not change. The fission neutron irradiated samples were investigated by SQUID and clear change in magnetization was measured. The 1.0 × 1022 n/m2 irradiation at JRR-3 increased the magnetization hysteresis curve, which means improvement of the critical current, and the over 1024 n/m2 irradiation degraded and made the strands no superconductivity. In case of Nb3Al strand, the proper heat treatment recovered the property remarkably [ABSTRACT FROM AUTHOR]