Response of Parallel‐Plate Ion Chambers to Radiation Pulses

摘要

A procedure for uncoupling the charge transport and electric field equations under certain restrictions of dose‐rate limitation and no recombination in a parallel‐plate ion chamber is given. A solution to the first uncoupled transport equation for a flat‐topped ionization pulse, including diffusion, is obtained by finding the appropriate Green's function, and the subsequent current densities and external circuit current are derived. The usual assumption of neglecting diffusion is shown to be valid for most cases involving ion transport by an examination of the general form of the external chamber current. Variations of the external circuit current with the radiation pulse width and the ratio of negative to positive ion mobilities are given. An attempt to ``fit'' an observed record shows marked deviation of the decreasing portion of the signal from the calculated one. This is probably due to the cessation of an appreciable free electron current after irradiation not taken into account by the calculation.