Measurements of the Energy Dependence of Prompt Neutron Emission from ²³³U, ²³⁵U, and ²³⁹Pu for E_n = 0.0005 to 10 MeV Relative to Emission from Spontaneous Fission of ²⁵²Cf

A series of experiments was performed to measure the dependence on the incident neutron energy of the average number of prompt neutrons emitted per fission from ²³³U, ²³⁵U, and ²³⁹Pu relative to the average number of prompt neutrons emitted in spontaneous fission of ²⁵²Cf. The incident neutron energy range was 0.0005 to 10 MeV. A white neutron source was generated by the Oak Ridge Electron Linear Accelerator, and the energies of the neutrons incident on the fissile samples were determined by time-of-flight techniques. In each experiment the samples, including the ²⁵²Cf standard, were contained in a fission chamber surrounded by a large volume (0.91 m³) of liquid scintillator loaded with gadolinium. The fission chamber detected the fission events, and the scintillator detected the accompanying prompt neutrons. The resulting data were analyzed to yield: _p(E) = _p(E) (fissile)/_p(²⁵²Cf). For ²³⁵U and ²³⁹Pu our results overlap, within the experimental uncertainty, the results of the evaluation of Manero and Konshin (1972), and in the case of ²³⁵U our data show the same general structure apparent in the evaluation up to 0.5 MeV. Our _p(E) for ²³³U does not show the structure near 0.2 MeV obtained by Manero and Konshin.