Measurement of reduced radii, depths, and optical densities of pits using computer analysis of micrographs of CR-39 plates etched after irradiation with 12C ion beam

Abstract

This work is a further development of our method, published in 2018, for computer analysis of micrographs taken from a plastic detector CR-39, etched after irradiation with a beam of 12C ions of energy 216 MeV/amu in the radiobiological research chamber of the ITEP-TWAC accelerator-storage complex. The aim of this work is to study geometric and optical parameters of pits in the etched plastic. This study is based on a new concept of reduced radii, which are the radii of the cross-section of inclined conical micro- and nano-pits at the points of intersection of their longitudinal axes and the etching surface of the detector; formulas for their calculations are derived. One CR-39 plate was irradiated in a radiobiological chamber filled with air, and eight plates were exposed at different depths of the chamber filled with water (phantom). 275,070 images of etched pores were found and analyzed in the plates. Differential frequency distributions of the reduced radii and depths of the pits and their average values on the etched surfaces of the plates are obtained. Formulas for nanodensitometry, microdensitometry, and macrodensitometry of pit images on micrographs are deduced. The dependences of the differential distributions and averaged values of pits optical densities on the ions passed ranges in the water phantom are calculated. Pairwise fittings by linear functions of the mutual dependences of the averaged values from each other and from the specific energy losses of ions are performed. It is shown that the most accurate linear fit is for the optical density-pit depth relationship.