High-sensitivity gamma-ray counting in activation analysis

In activation analysis, optimizing counting conditions can generally improve precision or increase the number of samples that can be counted, or both. Much is gained in sensitivity by using high-efficiency detectors. With care in selection of detector and shield materials, the only important source of environmental gamma-ray background is the interactions of cosmic-ray particles with the shield and the detector itself. Application of Cooper's criterion to two excellent modern detectors shows that for the ultimate sensitivity in quantitating a simple spectrum, high efficiency overwhelms good resolution, low background, or any other criterion of detector quality in the choice of detectors for a given measurement. In practice, the choice is not so simple when summing corrections are large, when multiplets are present which the detector cannot fully resolve, when the total count rate is high, when background peaks (not continuum) are important, when positioning uncertainty limits the accuracy, or when requirements of sample shape dictate the counting configuration. (author)