Developing a Fast Affordable Automatic Counting System of CR-39 Solid State Nuclear Track Detectors

Abstract

The CR-39 solid state passive nuclear track detector is a popular method to measure charged particle such as alpha and protons and uncharged particles such as neutrons, due to its low cost, robustness, track permanence, and insensitivity to gamma, X-ray, beta and electromagnetic waves. Traditional methods for processing CR-39 involve manual counting of the damage trails in the detector using an optical microscope: however, such methods are labor intensive and highly operator-dependent. The main aim of this research is to develop an affordable and fast automatic CR-39 track counting system. A set of CR-39 detectors with dimensions of 1.5 ´ 1.3 cm were exposed to 226Ra with an activity of 122 KBq for different periods of time. A full digital microscope with an LCD monitor of an area of 3.5” which acts as a 10x eyepiece was used to capture the images from the detectors. Three thresholds (size, Optical Density (OD) and circularity of the tracks) were applied to identify these tracks and facilitate in counting them. The automatic system was then compared to the manual counting method for verification. The P-value was higher than 0.05 (t-test: P-value for 2-tails = 0.99) that showed an insignificant difference between the manual and automatic counting. The system showed a good ability to find and count elliptical tracks using a simple algorithm depending on their circularity values. This system was seen to analyze the tracks effectively, taking less than one minute per detector. The system is almost fully automatic, fast and affordable.