Measurements of neutron energy using a recoil-proton telescope and a high-pressure ionization chamber

Two very different techniques for measuring the energy of neutrons in the energy range 0.1-10 MeV are presented and compared. A recoil-proton spectrometer is used to determine the energy spectra of neutrons produced by the d(4)-Be and p(4)-Be reactions down to the low-energy threshold of 0.7 MeV. The same radiation fields are also measured with a recently developed method using a high-pressure ionization chamber that can be used to determine the mean energy of the neutrons in a mixed neutron-gamma radiation field provided the gamma-ray absorbed dose fraction is determined independently. An intercomparison of the two methods shows that the high-pressure ionization chamber compares well and supplements the established recoil-proton spectrometer technique. The almost isotropic response of the chamber has enabled measurements to be made of the variation of mean neutron energy with depth in water for the two radiation fields.