Abstract
Bonner spheres are widely used to determine the energy spectrum of a neutron field. With the introduction of high-Z metal in moderator as a neutron multiplier, the effective energy range of Bonner spheres can be extended to GeV neutrons. Because of small active volume of the central probe, the detection efficiency of Bonner spheres is limited and impractical in certain field measurement applications. In this study, a set of Bonner cylinders was fabricated based on a high-efficiency cylindrical 3He proportional counter. The cylindrical arrangement substantially improved the detection efficiency of the spectrometer system, but inevitably yielded an angular dependence on the detector responses. Using a series of calculations and measurements, this study presents a systematic comparison between Bonner spheres and cylinders in terms of their response functions, detection efficiencies, angular dependences and spectrum unfolding.Besides, neutron dosemeters used for radiation protection purpose are commonly calibrated with 252Cf neutron sources and are used in various workplaces. In this study, the effect of the neutron spectrum on the accuracy of dose measurements was investigated. A set of neutron spectra representing various neutron environments was selected to study the dose responses of a series of Bonner spheres, including standard and extended-range spheres. By comparing 252Cf-calibrated dose responses with reference values based on fluence-to-dose conversion coefficients, this study presents recommendations for neutron field characterization and appropriate correction factors for responses of conventional neutron dosemeters used in environments with high-energy neutrons.