Abstract
The National Institute of Standards and Technology (NIST, Gaithersburg, MD 20878, USA) uses different extended sources, such as bar (parallelepiped) sources of high activity to calibrate the hyper pure germanium (HPGe) cylindrical detectors. The absolute full-energy peak efficiency and the source self-absorption have been investigated in this work by the use of compact analytical expressions for closed-end HPGe detectors and bar sources. The validity of these expressions is tested through extensive comparisons with the experimental values carried out in the NIST. The comparisons indicate that the direct mathematical method used in the present work is useful in the efficiency calibration of HPGe detectors with bar sources. (C) 2008 Elsevier B.V. All rights reserved.