Propagation of the uncertainties of sample position to the uncertainty of the counting efficiency in gamma-ray spectrometry

The uncertainties generated by inaccurate positioning of homogeneous cylindrical samples are propagated into the uncertainty of the counting efficiency. In this work general expressions describing the uncertainty of the counting efficiency in terms of the sample and detector properties are derived. The uncertainty of the counting efficiency generated by the uncertainty of the sample-detector distance is evaluated using the point detector concept. The uncertainty generated by the displacement of the symmetry axes of the sample and the detector is evaluated using the empirical radial dependence of the efficiency for point sources. Results are presented for some counting geometries resembling counting conditions frequently used in actual measurements. The results of the evaluations are compared to experimentally measured results and are briefly discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.