A Measurement of the Capture-to-Fission Ratio for Plutonium-239

The ratio of the neutron capture to fission cross section (α) has been measured for ²³⁹Pu in the energy range from 100 eV to 30 keV. Neutron time-of-flight techniques were used to obtain data with an energy resolution of approximately 10% at 10 keV. The data yield an average α = 0.80 ± 0.05 between 0.10 and 10 keV for an energy-independent incident neutron spectrum. Also, α data were obtained in the resolved resonance region below 100 eV.