Measurements of Pseudo-Decay-Constants of Trapped Neutrons in Small Graphite Systems at 77 and 194°K

Abstract

Neutron pulse die-away experiments for small graphite assemblies by using a pulsed "cold" neutron source technique were carried out for the purpose to measure the pseudo-decay-constants of trapped neutrons at the lowest Bragg-peak energy E_B of coherent scattering in graphite, and also to estimate the temperature dependence of inelastic. scattering cross section of neutrons at E_B. Experiments were carried out for 77 and 194°K graphite systems with dimensions from 40 x 40 x 40 cm³ to 30 x 30 x 20 cm³.
The experimentally determined pseudo-decay-constants showed distinct temperature dependence and good agreement with the theoretical inelastic scattering cross sections by Young-Koppel model of phonon frequency distribution of graphite at these low temperatures.