The HASL Ge(Li)-NaI(Tl) Low Level Counting System

A high efficiency Ge(Li) detector system with a NaI(Tl) annulus and "back-detector" has been developed to provide coincident and anti-coincident gamma-ray spectrometry of low level samples. Independent control of the three detector signals and a flexible logic arrangement allow optimum detection of non-coincident (Compton suppression) or coincident gamma-rays with either wide or narrow angles of correlation. This counting system and its application to the analysis of environmental samples is described.