A Tissue-equivalent Ionization Chamber for In-phantom Dosimetry

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Abstract
A tissue-" equivalent chamber designed for in-phantom dosimetry is described. The use of non-tissue-equivalent material has been restricted to amounts too small to perturb the radiation field significantly. Various chamber sensitivities were obtained by the use of gas fillings and electrodes of different properties, thus making it possible to distinguish among the absorbed doses from fast neutrons, [gamma]-rays, and the 14N(n, (n, p)14c reaction. The absorbed dose delivered to a cylinder of tissue by each component of an incompletely thermalized neutron beam was measured, A computer code has been developed to calculate the absorbed dose from X-rays and the 14N(n, p)14c reaction when a cylinder of tissue is irradiated with a beam of thermal neutrons. Measured results are compared with calculated results, and show good agreement.