### Abstract

Alpha particles emitted from radioactive sources are often measured using a 2pi counting geometry in order to determine the activity with a low deviation. The ratio C2pi/A (counting rate/activity) can, however, deviate from the theoretical value of 0.5 because of backscattering in the backing material, scattering and absorption of alpha particles in the source. The experimental counting rates are, therefore, corrected for these effects (backscattering for all sources, plus self-absorption for sources of non-negligible thickness) to determine the real source activity. However, the corrections needed for situations corresponding to alpha-particle sources in which the radionuclides are not deposited but incrusted in the backing material have not been considered. The aim of the present work was therefore to study the influence that incrustation in the backing can have on the total detection efficiency, and hence on the activity estimated for the source. To this end, we used the Monte Carlo computer code SRIM to model the behaviour of the alpha particles in the backing material.

###### Associate Professor

Alfonso Fernández Timón is Associate Professor and one of the senior researchers of the Optimization Algorithms Research Group GRAFO at the Universidad Rey Juan Carlos. Previously he was a fellow of the Metrological Stations Network and of the Radiological Surveillance Plan of the CSN at the University of Extremadura. His research interests range from the application of metaheuristics to solve combinatorial optimization problems to nuclear radiation metrology.