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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

As a large‐scale plasma experimental device is planned and designed, the importance of investigations on irradiation effect of 14 MeV neutron increases and an experimental database is desired to be piled up. Recently, intense streaming of fast neutron from ports are reported and degradation of superconducting magnet performance is anticipated. To investigate the pure neutron effect on superconducting magnet materials, a cryogenic target system was newly developed and installed at Fusion Neutronics Source in Japan Atomic Energy Research Institute. Although production rate of 14 MeV neutron is not large, only 14 MeV neutron can be supplied to irradiation test without gamma ray. Copper wires, superconducting wires, glass fiber reinforced composites are irradiated and the irradiation effects are characterized. At the same time, sensors for measuring temperature and magnetic field are irradiated and their performance was investigated after irradiation. This paper presents outline of the cryogenic target system and some irradiation test results.

Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and gamma ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and gamma ray irradiation on interlaminar shear strength and fracture mode are investigated using G‐10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength. A short beam test under three point bending was conducted at room temperature and 77 K. Neutron fluence of 3.91 × 1019 n/m2 was irradiated and the specimens did not show clear degradation of the strength. On the other hand, gamma ray irradiation of 1 MGy made the specimen weaker ...

Activation cross sections for the (n, n′) reaction were measured by means of the activation method at the neutron energies of 3.1 and 2.54 MeV by using a pulsed neutron beam. Target nuclei were 79Br, 90Zr, 197Au, and 207Pb, whose half‐lives were between 0.8 and 8 s. The cross section for the 90Zr (n, n′) 90mZr reaction was obtained for the first time in this energy range. The d‐D neutrons were generated by bombarding a deuterated titanium target with a 350‐keV d+ beam at the 80‐degree beam line of the Fusion Neutronics Source at the Japan Atomic Energy Research Institute. In order to obtain reliable activation cross sections, careful attention was paid to correct the efficiency for a volume source, and the self‐absorption of gamma rays in an irradiated sample. The systematics of the (n, n′) reaction at the neutron energy of 3.1 MeV, which could be predicted within an accuracy of 50%, was proposed on the basis of our data.

Activation cross sections for deuteron‐induced reactions on aluminum, copper, and tungsten were measured by using a stacked‐foil method. The stacked foils were irradiated with deuteron beam at the AVF cyclotron in the TIARA facility, JAERI. We obtained the activation cross sections for 27Al(d,2p)27Mg, 27Al(d,x)24Na, natCu(d,x)62,63Zn, 61,64Cu, and natW(d,x)181–184,186Re, 187W in the 22–40 MeV region. These cross sections were compared with other experimental ones and the data in the ACSELAM library calculated by the ALICE‐F code.

A new spectrometer has been developed, including a pencil‐beam 14‐MeV neutron source and a telescope system with two SSDs of ΔE and E, in order to measure double differential charged‐particle emission cross sections (DDXs). The spectrometer can supply quite good performance, i.e., low minimum measurable energy of below 2 MeV for alpha particles and a very high S/N ratio over 10. Highly accurate charged‐particle emission DDX data can thus be expected to be measured by this spectrometer. From the test measurement for aluminum, the validity was confirmed by comparing the angular differential cross section (ADX) and the total charged‐particle emission cross section with other data. Also, the measurement for beryllium has been carried out. From the result of the measurement, the acceptable agreement with the evaluation was confirmed in the energy spectrum. The precise branching ratio of the breakup nuclear reaction of beryllium is now being analyzed from the obtained DDX data.