The Role of Sample Geometry on Ultra-Low Alpha Particle Emissivity Measurements

The detection efficiency of an ionization counter and the resulting energy spectra of samples can be dependent on the sample geometry. This is especially important for samples that are large compared to the size of the detector since some of the alpha particles emitted near the edge of the samples might not be collected if their trajectories fall outside the active area of the detector. We examine this effect in detail by measuring the alpha particles detected for rings and disks of various sizes, and compare the results to analytical and Monte Carlo models.