The Age of Fission Neutrons to Indium-Resonance Energy in Water

The age of fission neutrons to indium-resonance energy (1.46 eV) was measured in water using a plane fission source of finite diameter and essentially infinite plane detectors. This is equivalent to a measurement using axial detectors with an infinite plane source. Thus, unlike recent measurements which used axial detectors with large plane sources, these results do not require calculated corrections to extrapolate to infinite-source geometry. The remaining corrections are small and well understood. The age measured in this experiment was 26.48 ± 0.32 cm² at a density of 1.0 g/ml.