Neutron dosimetry with detectors of finite size. II. Experiments and calculations

In a previous article a theory for detector response in fields of fast neutrons was presented. In the present paper this theory is subjected to experimental tests. For detectors of sizes comparable to the ranges of the neutron produced charged particles the theory predicts the variation of the detector response with detector size and elemental composition of the detector. A tissue-equivalent ionization chamber exposed to a field of 252Cf neutrons was used in the experimental tests of the theory. The size dependence of the response was investigated by varying the chamber gas pressure and the effects of different elemental compositions (mainly hydrogen content) was investigated by using different gases in the chamber (H2, CH4, TE-gas N2, Air, CO2, and Ar). The theory was evaluated both by using chord length distributions to characterize the chamber cavity and with a simplified version using a single mean chord length. The agreement between theory and experiment is generally good.