A new approach for the detection of charged particles by photographic recording systems—first applications in corpuscular physics, biology and electron microscopy

The activation procedure consists not only in the introduction of more or less sophisticated treatments in the development phase, but also in the setting up of a specific ionographic methodology which will be shortly described. The working hypotheses which led to the formulation of the so-called activation treatments will be outlined, notably the concept of the stable sub-latent image. The consequences of the activation procedure in ionography will be shortly recalled, e.g. the drastic increase of the signal/noise ratio ranging from 1.5 to 20 and more, as well as the remarkable stability of the fog. The interest of the activation procedure for Corpuscular Physics as well as for the Life Sciences will be illustrated by first applications in autoradiography, electron microscopy and microdosimetry. As far as the autoradiographic methods are concerned, the considerable increase in efficiency and in resolution results in a drastic decrease of the exposure time or/and of the quantity of tracer elements applied, as well as in the possibility to carry out studies implying the detection of very small amounts of activity. The activation of the latent image can also be applied to exposed electron microscope photographic plates in order to allow a non-destructive observation of very sensitive specimens (macromolecules, etc.). In the field of Corpuscular Physics, the activation treatments led to the detection of secondary events distributed along α tracks of medium and low energy recorded in nuclear emulsions. An analytical study confirmed the hypotheses that the largest part of these protuberances are tracks of electrons and H-nuclei ejected by the incoming particle. These investigations are intended to lead to a description of the ionizing track pattern as well as to the interpretation of experimentally determined fluctuations of the track width.