Fission-to-Indium Age in Water

A redetermination of the age τ (= ⅙ 〈r²〉) for neutrons of indium-resonance energy (1.46 ev) from a point U²³⁵ fission source is reported. Foils were irradiated in a geometrically simple arrangement in the Penn State Reactor pool, and counted in a standard manner. The value obtained, τ = 27.3 ± 0.9 cm², is in better agreement with current theory than those from previous measurements. The spatial distribution found here differs most markedly from those observed in previous experiments by having a larger slope in the region within a few centimeters of the source.