Supralinearity and particle discrimination in nuclear emulsion

Nuclear emulsions may be desensitized in manufacture and/or may be so processed as to discriminate against small latent image sites; to yield supralinear sensitometric response after x-irradiation; and to discriminate against lightly ionizing radiations in favor of heavily ionizing particles. In a circumstance where one electron passing through an emulsion grain is unlikely to generate a latent image sufficiently large to yield a visible grain after development, some larger number of electrons is required, resulting in “many-hit” statistics, supralinearity, and particle discrimination: for lightly ionizing particles are not likely to generate more than one δ-ray (secondary electron) in their passage through or near a grain. Since these properties are analagous to the response of many biological cells to ionizing radiations, such emulsion-developer combinations have the potential to mimic the response of biological systems to particulate radiations of different charge and speed.