New time-of-flight measurements made with an intense source

In an experiment in Nevada in June 1965 a nuclear device with a yield equivalent of 1.2 kilotonnes of TNT provided the neutron source for time-of-flight measurements over a path of 185 m in vacuo. To exploit the combination of high flux and high energy resolution, new recording techniques have been required. Because more than a million data points are acquired in any one exposure of a set of targets, the general problems of data retrieval and processing have required special attention. Measurements of fission cross-sections of the nuclides 233U, 235U, 239Pu, 240Pu, 241Pu, 241Am, 242Am are reported. In addition, capture-to-fission ratios of 233U and 240Pu are reported. The neutron energy range is 10 eV to 2 MeV. Individual resonances are resolved in the 100-eV range. Fission data in the resonance region are characterized by lower minima than are reported by most earlier investigators, indicating more favourable signal-to-background ratios. A unique feature of these experiments is the high rate of data acquisition, which allows cross-section measurements on short-lived nuclides. Even for the long-lived nuclides, these experiments provide an abundance of data required in current nuclear technology - data that could otherwise be acquired only by years of tedious measurement. (author)