Experimental studies of self-absorption and backscattering in alpha-particle sources

Several theories have been developed to explain why the counting efficiency of a 2π geometry alpha-particle detector is not 50%. These theories include backscattering and self-absorption as the causes of this discrepancy. Experimental measurements were made in order to confirm their predictions. In general, there was very good agreement between theoretical predictions and experimental results for the effects due to backscattering. When the thickness of the sample is considerable, self-absorption must be carefully taken into consideration to correctly measure the true activity concentration of the solution used to prepare the source. Experimental measurements were made and a method to perform the self-absorption corrections is proposed. These corrections are essential in calculating the activity of sources containing long half-life nuclides. The experimental results give reliability to methods characterizing alpha-particle sources without the use of a primary standard for the calibration of the experimental setup.