Scintillator-filled etch-pit method of counting radon-decay alpha tracks, and calibration in a diffusion chamber

Abstract

A semi-automatic and simple method, based on the original Harvey and Weeks technique (1982) of counting scintillator-filled track etch-pits, has been used to count radon-produced tracks in CR-39. The linearity between the exposure time to radon for tracks densities of up to ∼6×10 4 tracks cm −2, and scintillation counts rate, has led us to a calibration of the detectors. We obtained K s=0.0865±0.0001 scintillation counts s −1 per unit track density (tr.cm −2), and a constant of proportionality for exposure to radon and its daughter products, K T=75±1 Bqm −3h per (tr.cm −2). The technique thus offers a quick, reliable and inexpensive method for counting radon-produced α-tracks in CR-39. We have also attempted automatic coating of the etch pits by using the cathode sputtering method, in order to fill the holes uniformly and homogeneously. An attempt was also made to use an ultraviolet source (366 nm wavelength) for the readout, rather than the strong α-source, thus avoiding interference by secondary emissions from CR-39 of high track-densities.