A THREE-DETECTOR MEASURING SYSTEM USING A PURE-Ge DETECTOR

Abstract

A three-detector measuring system making use of a pure- Ge detector combined with two Si ( Li ) detectors has been developed. The efficiency curve of the pure- Ge detector has been determined easily as relative efficiencies to those of the existing Si ( Li ) detectors, since this system allows us to analyze a sample with the pure- Ge and the Si ( Li ) detectors simultaneously under the same irradiating conditions. It is found that detection efficiencies of the pure- Ge detector decrease just above the absorption edge of Ge owing to absorption of X-rays in the dead layer of the detector. Accuracy of the efficiency curve thus obtained was confirmed by analyzing a few samples whose elemental concentrations are known. It is confirmed that a pure- Ge detector can be used in place of a Si ( Li ) detector for the purpose of analysis of elements Z ≧ 19, since its energy resolution is almost equal to that of a high-performance Si ( Li ) detector and efficiencies at high energies are far better. Moreover, it becomes possible to detect prompt γ-rays and to analyze light elements such as fluorine, which arouses much interest from the point of view of environmental contamination. Detection limit of fluorine is found to be less than 0.1 ppm for water samples.