Measurement of cold neutron spectra using a model cryogenic moderator of the IBR-2M reactor

The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures of 10–50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the IBR-2M reactor and to obtain the cold neutron yield as a function of the moderator temperature. Satisfactory agreement between the experimental and calculated neutron spectra at a mesitylene temperature of 20 K has been obtained; the ratio of cold neutron intensities at 10 and 50 K is ∼1.8.