Some geometrical-optical properties of micro- and nanopores obtained by computer analysis of micrographs of plastic detectors CR-39 etched after irradiation with a beam of accelerated 12C ions
This work was carried out on the basis of the etched pore recognition method published in our work. Eight CR-39 plastic plates were fixed at various distances from the ion beam entry window into a bio-chamber filled with water. Then they were etched, dried and scanned by the computer-MPE-1 microscope system with an integrated video camera. About fifty micrographs were done from each side of the plates and recorded in img-files. The modified code of inscribed ellipses into the image contours of the found pores and calculated the sizes of their major and minor axes. The definition of reduced pore radius was introduced and a formula was obtained for its calculation. Knowing r, the bulk etching rate of the material and the etching time of the plastic, one can find the depths L of micro- and nanopores. Thus, the distribution of pores over the reduced radii r and depths L, their values averaged on each surface of the plates, were found as functions of their distances S from the window of entry of ions into the chamber. Then the formulas for macrodensitometry, microdensitometry and nanodensitometry were derived. The dependences of the distributions and average optical densities on the distance S in the water chamber were calculated. Pairwise fittings by linear functions of the mutual dependencies of the averaged values and on (dE/dS) were carried out. The most accurate fit was achieved for the dependence of the averaged optical density <D(S)> on the average pore depth <L(S)>. The worst fit is the approximation of the found average values by a linear dependence on the specific energy loss. This confirms the fact that the probability of the appearance of the response of detectors with high sensitivity is a nonlinear function of the specific energy loss. It is known that CR-39 plastic refers specifically to such detectors and to calculate its local response it is necessary to use the many-hit model.