Dosimetry for Fast-neutron Irradiations of Cultured Cells and Intact Animals

Abstract

For an accurate determination of the absorbed dose in fast-neutron irradiations of living organisms, tissue-equivalent ionization chambers were used. Three different gas mixtures have been suggested for use as filling gases for these chambers. To test the equivalence of these gases, two series of experiments were performed with mono-energetic neutrons produced by the D-D and the D-T reactions. Firstly, the relative contributions of ionizing particles, produced in either the wall or the gas, to the current measured in the ionization chamber were investigated. Secondly, with the different gas fillings the response of the chambers was studied for various neutron energies. The relative contribution of particles from the wall of the chamber was found to increase considerably with increasing neutron energy. Consequently, identical dose-rates (for equal neutron flux densities) were measured in 15 mev neutron irradiations when the ionization chamber was flushed with different tissue-equivalent gas mixtures. For 3 mev neutron irradiations a relatively lower measured dose-rate was found for one of the tissue-equivalent gas mixtures.