A rapid reading technique for nuclear particle damage tracks in thin foils

Abstract

The low background of damage track detectors allows them to measure low integrated fluxes of charged particles or neutrons. When good statistical accuracy is desired, the long times required for visual track counting under the microscope may seriously limit the number of measurements, particularly when the track density is low. A technique has been developed for automatically counting etched tracks that pass through a thin film. Very simple and inexpensive equipment is required. The insulating film is placed between a plane, high-voltage electrode and a thin layer of Al. A spark, passing through the film along a damage track, evaporates a hole in the Al. A second spark is prevented from starting through the same hole, so that the discharge passes successively along each track and then stops. Sparks are counted with a scaler. The pattern of holes in the Al provides a visible replica of the pattern of tracks. Track densities from background level to 3000 tracks/cm² can be measured. Areas up to 100 cm² are usually counted in less than 10 seconds, with an error of a few per cent in the number of tracks. The technique has been applied to neutron dosimetry and to measurements of angular distributions in photofission.