EXPERIMENTAL INVESTIGATION OF THE NM-64 NEUTRON MONITOR

Abstract

A comprehensive experimental study has been made of the NM-64 neutron monitor. The counting rate has been measured as a function of the thickness of the reflector, of the separation of the counters, of the thickness of the inner moderator, and of the gas pressure in the counters. It is shown that the figures given in the internationally approved specification represent a satisfactory optimization of the design. The counting rate of the NM-64 monitor is found to be 3.3 times that of an IGY monitor of the same horizontal area. The origin and movement of both fast and thermal neutrons within the monitor have been investigated using cadmium sheets and by studying events producing counts in more than one counter.