The Influence of Grain Size on the Response of Emulsions to Ionizing Radiation

Abstract

The relation between speed and emulsion grain size is examined for exposure of a grain size series of spherical emulsions to electrons in the range 25-100 keV, to X-rays in the range 20-290 kV_p, and to cobalt(60) 1.2 MeV gamma (γ)-rays. II was observed for films processed in a black-and-white developer that the speed increased up to the largest size studied, which had a mean grain projective area of 10 pur, broadly in line with expet tations from simple theory. II was evident that the use of chemical sensitization had little impact on --peed for the fine grain emulsions of size 0.05 µm² exposed to 20 kV_p X-rays, but was crucial for all the emulsions exposed to 1.2 MeV γ-rays.

The impact of cobalt(60) on tabular grain emulsions given colour development was studied also because of its relevance to the influence of natural background radiation, there was an increase in speed with grain size but the trend was identical for light and cobalt(bO) radiation. A single tabular emulsion was also examined after these two types of exposure in order to reveal the relation between speed and grain size for the different size classes within the emulsion. Speed increased with increasing grain size, but not as much as expected, and the trends for the two types of exposure were similar, iusl as in the case of the grain size series of tabular grain emulsions.