An automatic device for measuring etch pit density on cellulose nitrate film

We developed an automatic device to measure etch pit density on cellulose nitrate film, which consisted of microscope, monochrome video camera, image processing device, monochrome display and personal computer. For 1-3 MeV energy alpha particle, high reproducibility of automatic counting was confirmed. In case of 4 MeV energy alpha particle, results of automatic counting were unstable. Counting efficiency for 4 MeV energy alpha particle can be decreased with increasing threshold level which was used when image data was converted into binary data. Correction for loss of etch pit density due to overlapping etch pit image was not necessary up to about 8000 tracks cm-2 in case of about 10 μm diameter etch pits. Radon concentration can be estimated up to 120 Bqm-3 without correction due to overlapping etch pit image, when the measurement was carried out for 2 months with an electrostatic integrated radon monitor. (author)