Fully automated image analysis of etched tracks in CR-39

Abstract A comprehensive analysis system has been developed for analysing nuclear particle tracks in plastic. The system has two main components. The first, described in this paper is an image analysis scanning system purpose built for analysing etched tracks, and featuring sophisticated track discrimination and measurement facilities. The second, published separately, covers new techniques for track analysis designed to extract the maximum possible information from the etch pits. The system is used in a wide variety of applications involving low level detection of nuclear particles. High spatial resolution is achievable, together with energy resolution to better than the straggling limit. The image analysis system is capable of rapid, fully automated scanning, identification and measurement of etched nuclear particle tracks in plastic, at a rate of up to four frames per second, each track taking ∼ 30–100 ms to process. The characteristic parameters of etch pits are measured with a precision exceeding that of a skilled human observer. The analysis has several unique features, in particular a sophisticated dynamic edge detection algorithm permitting accurate measurement of the edge of tracks even in the case of single pixel noise exceeding the underlying contrast in the object. The system differs from all its predecessors in that it is able to analyse etch pits even in the case where the particle is close to etching threshold and the etch pit merges asymptotically with the plastic surface, thus enabling α-particle and proton tracks to be correctly processed. Reliable and efficient selection criteria enable etched tracks to be discriminated from non-track features. Images of overlapping events are separated using an algorithm exploiting the symmetry of real tracks.