Optimization of counting time in the radioactivity measurement of gaseous samples with inner counting method

For absolute radioactivity measurements of gaseous radioisotopes using the ''diffusion in a long proportional counter'' method devised by the present authors, the counting time is optimized by balancing the diminution of the statistical error caused by prolonging the counting time and the increase of the counting loss caused by diffusion of the sample gas into the counter ends of lower electric field intensity. The counting loss is estimated from the diffusion behavior of the gas through the counter. The optimized counting time is that which minimizes the total error consisting of a statistical part and a counting time loss part. Trial measurements made applying the optimized counting time proved to provide good agreement with corresponding data obtained with the ''position-sensitive proportional counter'' method also devised by the present authors. (orig.)