A beta-gamma coincidence system consisting of a 2π plastic beta detector and a Ge(Li) detector, is described. Such a system allows for a drastic reduction of background (~70 times) as well as of Minimum Detectable Activity (~7 times). An integral background (50-1500 keV) of less than 0.1 cps is obtained. The difficulty of the method, otherwise simple and inexpensive, is the precise determination of beta detector efficiency. (C) 2000 Elsevier Science Ltd.
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