Enhanced beta-gamma coincidence counting gas cell

The automated radioxenon sampler/analyzer (ARSA) uses a highly compact, high efficiency beta-gamma coincidence detector to detect /sup 133/Xe, /sup 131m/Xe, /sup 133m/Xe and /sup 135/Xe for treaty monitoring and environmental sampling. This system has shown itself to he reliable and robust in several field exercises. However, from a maintenance and quality assurance/quality control (QA/QC) standpoint it suffers from a very detailed photo-multiplier-tube gain matching regime. In an effort to upgrade and simplify the current beta-gamma coincident detector, Pacific Northwest National Laboratory (PNNL) has developed a simplified but equally effective well-type detector. Initial comparison between three different well detectors has been performed. Along with the well gamma-ray detectors, a new plastic scintillation gas cell was constructed. The spectral resolution and efficiency obtained from this new design has been demonstrated to be as good as or better than the original ARSA design with greatly improved calibration and maintenance characteristics.