Measurement of (n, n′) reaction cross-sections of 79Br, 90Zr, 197Au and 207Pb with pulsed d-D neutrons

Activation cross-sections for the (n, n′) reaction were measured by means of the activation method at neutron energies of 3.1 and 2.54 MeV using a pulsed neutron beam. The target nuclei were 79Br, 90Zr, 197Au, and 207Pb whose half-lives were between 0.8 and 8 s. The value of the 90Zr(n, n′) 90mZr reaction was obtained for the first time. In order to confirm the pulsed neutron beam measuring method, the cross-section data of 79Br and 197Au were compared with previous data obtained using a pneumatic sample transport system. The results of this comparison were in agreement within the range of experimental error. The d-D neutrons were generated by bombarding a deuterated titanium target with a 350-keV d+-beam at the 80° beam line of the Fusion Neutronics Source (FNS) 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 irradiated samples. The systematics of the (n, n′) reaction at a neutron energy of 3.0 MeV, which can predict cross-section of (n, n′) reaction with an accuracy of 50%, was proposed for the first time on the basis of our data.