SCINTILLATOR-FILLED ETCH-PIT METHOD OF COUNTING RADON-DECAY ALPHA-TRACKS, AND CALIBRATION IN A DIFFUSION CHAMBER

A semi-automatic and simple method, based on the original Harvey and W eeks 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 track densities of up to simila r to 6x10(4) tracks cm(-2), and scintillation count rate, has led us t o a calibration of the detectors. We obtained K-s=0.0865+/-0.0001 scin tillation counts s(-1) per unit track density (tr.cm(-2)), and a const ant of proportionality for exposure to radon and its daughter products , K-T=75+/-1 Bqm(-3)h per(tr.cm(-2)). The technique thus offers a quic k, reliable and inexpensive method for counting radon-produced alpha-t racks in CR-39. We have also attempted automatic coating of the etch p its by using the cathode sputtering method, in order to fill the holes uniformly and homogeneously. An attempt was also made to use an ultra violet source (366 nm wavelength) for the readout, rather than the str ong alpha-source, thus avoiding interference by secondary emissions fr om CR-39 of high track-densities.