Nuclear Science and Engineering · 1973 · 21 citations · 0 references
Natural SciencesPhysicsNuclear PhysicsRadiation DetectionRadiation MeasurementCross Section DataNuclear Cross SectionsNuclear FissionNuclear SpectroscopyCapture Cross SectionsDetectorsFission Cross SectionsFission ReactionsNeutron Capture Cross SectionRadiative Capture ReactionsResonance Cross SectionsResonance Parameter Evaluation
The radiative capture cross section of 238Pu has been measured from 18-eV to 200-keV neutron energy. A time-of-flight experiment with a 306-m flight path was carried out in conjunction with the underground nuclear explosion Persimmon. Fission-fragment detectors viewed a thin 238Pu target to measure the fission cross section, while modified Moxon-Rae detectors viewed a second, thicker 238Pu target to measure the gamma-ray emission. Subtraction of the fission gamma-ray contribution from the Moxon-Rae signal yielded the contribution due to radiative capture. Single-level area analysis of the measured fission and capture cross sections gave values for the neutron and fission widths of 49 resonances below 500 eV, under the assumption of a known, constant radiative capture width. The s-wave neutron strength function was determined to be (1.27 ± 0.25) × 10-4. The derived fission widths exhibit a distinct maximum near 300-eV neutron energy. At higher energies, the fission-to-capture ratio shows pronounced intermediate-structure peaks attributed to second-well effects in the fission barrier.