A new type of neutron spectrometer

Abstract Neutrons are detected in a small Li6I(Eu) scintillator placed at the center of polyethylene moderating spheres with sizes ranging from 2 to 12 inches in diameter. The efficiency of this neutron counter has been experimentally determined using monoenergetic neutrons from thermal energies to 15 MeV. The counter has excellent energy sensitivity from 0.1 to 2 MeV and is particularly useful for determining the shapes of continuous neutron spectra. The pronounced difference in the efficiencies for the five sizes of spheres which have been calibrated provides a basis for accurate neutron energy determination. The good γ ray discrimination of the counter allows it to be used with a radium-beryllium neutron source. Neutron spectra from a variety of sources have been determined with this counter. These include the two groups of neutrons from the C14(p,n)N14 reaction, the evaporation spectrum of the neutrons from the reaction Rh103(p,n)Pd103, the energy spectra of inelastically scattered neutrons, and the neutron spectrum from the scattering of fast neutrons by the floor and walls of a building.