Ionization efficiency of a gas-flow ion chamber used for measuring radioactive gases by Monte Carlo simulation

The ionization efficiencies of a cylindrical ionization chamber have been calculated using a Monte Carlo electron-photon transport code. The results agreed well with experimental values for radioactive gases. The present calculational procedure can be applied to the estimation of ionization efficiencies for radioactive gases, such as the short half-lived nuclides and positron emitters, which have been difficult to estimate through experimental calibrations. It can also be applied to evaluations of efficiencies in gases other than air. This paper describes the calculation method and results, and also presents the effects of shape and volume variations of the ionization chamber.