Optimization of cylindrical sample geometry in determining the radioactive activity of environmental soil samples by using a Broad Energy Germanium detector

Abstract

This paper describes the optimization of the geometric parameters of cylindrical geometry to maximize the detection efficiency for given sample volumes with a BEGe detector. A Monte Carlo model was developed and the detector efficiencies were studied for different sample geometries. The optimal sample dimensions that maximize the detection efficiencies have been determined by changing the sample dimensions through consecutive studies. The results show that the maximal detection efficiency depends on the appropriate selection of sample dimensions for a given sample volume. For the cylindrical geometry, the maximal detection efficiency can be obtained with the average sample radius/sample height value of about 1.75 (1.61 ∼ 1.91) for the corresponding given sample volume ranging from 150 to 400 cm3. Further studies show that the optimal sample height for a fixed cylindrical radius strongly depends on the measuring photon energy, and simply increasing the sample height does not generate higher full-energy peak net count rate. At last, optimal sample dimensions for the cylindrical geometry are recommended for a given detector specification with different sample volumes and photon energies.