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Large Area Alpha Sources with a Lip: Integral Counting and Spectral Distortions



Lynne E. King, Ryan P. Fitzgerald, Ronald Tosh


The detection efficiency for large area alpha sources with adjustable heights of a raised lip around the edge were measured by 2π gas-filled proportional counter. The variations in low- energy spectral shape were modeled using a Geant4 radiation and charge transport Monte Carlo simulation, to enable extrapolation of the spectrum to zero energy. Changes in the spectrum gain in the presence of a lip were explored using COMSOL Multiphysics finite-element analysis and qualitatively reproduced an increase in peak height due to an increasing height of the source lip. A spectrum analysis procedure was developed to perform integral counting on sources with a lip. The experimental results were used to validate the model, which was then used to predict the changes in 2π counting efficiency for other source-lip geometries.
Applied Radiation and Isotopes


proportional counter, large area sources, source geometry, Monte Carlo


King, L. , Fitzgerald, R. and Tosh, R. (2017), Large Area Alpha Sources with a Lip: Integral Counting and Spectral Distortions, Applied Radiation and Isotopes, [online],, (Accessed April 15, 2024)
Created August 30, 2017, Updated October 12, 2021