Transfer of detector efficiency calibration from a point source to other geometries using ETNA software

摘要

The quality of the results of gamma spectrometry measurement depends directly onthe accuracy of the detection efficiency in the specific measurement conditions. Traditionally,measurements are performed in gamma-ray spectrometry by the so-called relative method, accordingto which a standard sample is first used for calibration; the standard sample should match themeasured one in all the important characteristics, such as its size, chemical composition and density.The preparation of the standard is costly and time consuming, especially if the laboratory is requiredto measure samples with different geometries. Experimental efficiency calibration is restricted toseveral measurement geometries and cannot be applied directly to all measurement configurations.An alternative possibility of being able to compute the efficiencies is thus highly desirable. Thepurpose of this work is to examine the applicability of the efficiency transfer method for thecomputation of the efficiency in various measurement geometries on the basis of the measuredefficiency for reference point source geometry. For this, the ETNA (Efficiency Transfer for NuclideActivity measurements) code is used. In this study the transfer method was applied for thecomputation of the efficiency of a high purity germanium (HPGe) detector for a point source placedat several distances and in addition for volume sources of different compositions and densities on thebasis of the reference efficiency measured for a point source located at 10 cm distance from thedetector. The experimental efficiency curves were compared with the prediction of the ETNA software.