Automation of a Readout System for Passive Radon Dosemeters

An automatic counting system for etched foils from passive radon dosemeters is described. It is built using standard low-cost components: a microscope with TV camera and an IBM XT compatible personal computer with a video card. Our software package can recognise tracks, determine their extent, count the tracks and make a histogram of the track distribution. Problems like resolving adjacent tracks and distinguishing real tracks from dust and fluctuations in foil transparency have been resolved. The program, written in compiled BASIC, matches these requirements with a counting time varying between 1 and 2 min, depending on track density and the options used. It is menu driven and, when measuring time and calibration parameters are available, the radon concentration is directly calculated in Bq.m-3.