title: Analytical calculations of the solid angles subtended by a well-type detector at point and extended circular sources.
abstract: Knowledge of the solid angle (and consequently, the geometrical efficiency) is essential in all absolute measurements of the strengths of radioactive materials and to calibrate detectors. The method of high-efficiency gamma counting by means of well-type HPGe and NaI (Tl) detectors is widely used and has proved a powerful tool, particularly when low-activity, small-volume environmental samples are to be analyzed by gamma-ray spectrometry. In the present work, we introduce a direct analytical method for calculating the solid angle subtended by a well-type detector at axial point, non-axial point, extended circular disk and cylindrical sources. The validity of the derived analytical expressions was successfully confirmed by the comparisons with some published data (experimental and Monte Carlo).
authors.affiliation: Physics Department, Faculty of Science, Alexandria University, 21121 Alexandria, Egypt. mabbas@physicist.net <mabbas@physicist.net>
authors.forename: Mahmoud I
authors.initials: MI
authors.lastname: Abbas