The effect of solid angle on the reproducibility of an experimental set-up in prompt gamma-ray neutron activation analysis

A Monte Carlo method which allows the calculation of the solid angle subtended by a collimated detector from surface and distributed sources is presented. The method utilizes total variance reduction and its validity is demonstrated for cylindrical and disc sources. The effect of rotation and displacement of the source on the solid angle is investigated for small and large sources. A measure of tolerance on the reproducibility of the experimental set-up in activity quantification is discussed. (author)