Image formation in track-etch detectors—I. The large area signal transfer function

Abstract

Abstract A physical model of image formation in solid state nuclear track detectors has been formulated. Using this model the large area signal function (optical density over a large area) is calculated. The theoretical calculations are verified by experiments with LR-115, CA-8015 and CR-39 detectors using the 10 B ( n , α) reaction. It is found that the optical density increases approximately linearly with the logarithm of exposure (defined as the product of the average visible track area and track density) within exposure limits of 0.5–5. At higher exposure, the optical density shows different behaviour in thin and thick detectors. A relatively sharp transition to saturation takes place in thin detectors. In thick detectors a bell-shaped function is found with a maximum near an exposure of five. The decrease of optical density at higher exposure is explained as the combined effect of track overlapping and the optical properties of a single track. The slope of the curve, which determines the contrast of the detector, is found to be dependent on the exposure, the type of detector, the type and energy of the charged particles and the etching conditions.