Some modifications to Sima's model for total efficiency calculation of well-type detectors

Some modifications are presented to Sima's simple analytical model for the calculation of the total detection efficiency of a well-type γ-ray detector, aiming at improving its accuracy and broadening its applicability. The modifications pertain to some general improvements in the photon transmission probabilities through absorbing materials and implementation of specific equations for solid angle and mean path length through materials that describe the case of eccentrically positioned sources as well as volume sources. In particular, some improvement is achieved by implementing a contribution from elastic scattering effects. (author)