A new scanning system for large area track-etch detectors

A rapid automatic system based on a new method is developed to scan etch-holes on large area plastic track detectors. Deeply etched CR39 sheets are first black-dyed and then are exposed to an intense visible light. Optical filters make a sharp contrast between the light which passes through the etch-holes and the background infrared light through the plastic. The picture taken by a CCD camera is digitized and stored in a memory. After simple zero-suppression the data are read out by a personal computer, followed by an on-line analysis to determine the positions and brightness of the holes. With this system an etch-hole as small as 10 μm can be detected and a sheet of size 300×300 mm can be scanned within 10 s.