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A. Nishimura, T. Takeuchi, S. Nishijima, N. Koizumi, G. Nishijima, K. Watanabe
14 MeV Neutron Irradiation Effect on Superconducting Properties of Nb3Sn Strand for Fusion Magnet
Date of publication:
22 IAEA Fusion Energy Conference, FTP/P1-22
Using 14 MeV neutron source and fission reactors, neutron irradiation tests of Nb_3Sn strand were carried out. The maximum fluence was 2.65 x 10^21 n/m^2 for 14 MeV neutron and 4.3 x 10^24 n/m^2 for fission neutron. By the irradiation with 14 MeV neutron, increase of I_c (1.45 times at 14 T), no change of B_c2 (under 100 mA) and degradation of T_c (0.2 K) were measured. Magnetization of irradiated samples at fission reactors suggested that 1.0 x 10^21 n/m^2 irradiation would increase IC but 1.1 x 10^24 n/m^2 irradiation would degrade IC. The irradiation of 4.3 x 10^24 n/m^2 made Nb_3Sn strand non superconductivity any more. These facts were considered to be caused by strengthening of pinning force and disordering of A-15 crystal with knock-on effect of fast neutron. Higher neutron fluence would increase IC but destroy the crystal at the same time.
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