MONTE-CARLO SIMULATION OF SEVERAL GAMMA-EMITTING SOURCE AND DETECTOR ARRANGEMENTS FOR DETERMINING CORRECTIONS OF SELF-ATTENUATION AND COINCIDENCE SUMMATION IN GAMMA-SPECTROMETRY

A Monte Carlo simulation technique has been developed for gamma-spectr ometric measurement systems which allows calculation of photon path le ngths in source and detector as well as total efficiency. From these p arameters correction factors for self-attenuation and coincidence summ ation can be estimated. The calculations require only readily availabl e data e.g., dimensions and relative positions of the gamma-emitting s ource and the detector as well as the appropriate emission probabiliti es of the gamma lines under study. The simulation involves relating th e point of emission and the path of the photon to an axis of symmetry and therefore applies to any axially symmetric arrangement of source a nd detector. The calculated total efficiency curves for well-defined a rrangements of point source and detector are practically identical to those reported in the literature. Similarly, correction factors for co incidence summation of Na-22, Co-58, Co-60, and Y-88 as point cylindri cal volume and Marinelli beaker sources agree very well with values es tablished by experiment or by a different model approach. In addition, total efficiency curves and average path lengths of photons in the so urce are given for several other measurement systems with Ge(Li) or p- type (Hp)Ge detectors.