Supralinearity in nuclear research emulsions

Nuclear emulsions processed in discriminating developers, intended to suppress small latent image sites, exhibit supralinear sensitometric blackness-exposure curves, whose character varies according to developing time, concentration, and composition, yielding hittedness ranging from 1 to 8, singly and in combination. These emulsion-processing combinations display the phenomena called ion-kill (sensitization by the transit of a single charged particle) and gamma- kill (sensitization by the overlap of secondary electron paths, whether from x-rays or from the delta-rays of heavy ions) in radiobiology. Here emulsions are blackened by x-rays when these same plates reveal no electron tracks, or no alpha-particle tracks, or even no fission fragment tracks. The supralinearity of the emulsion response to x-rays, and the consequent suppression of low LET radiations suggest that these materials have the potential to mimic the response of biological systems to particulate radiations of different charge and speed.