The Radioactivity of Solids Determined by Alpha-Ray Counting

Abstract
The complete theory of alpha-ray counting for thin and thick radioactive sources is developed. Tables of the numerical constants required for the interpretation of practical measurements are given. Apparatus and experimental verification of the theory are described. Several new methods for determining the thorium content of geological samples are described. Analyses of a suite of igneous rocks show Th contents between 3.9 and 16.5×106g Th per g, with an average Th/U ratio of 7. Therefore thorium is more important in age and geothermal problems than uranium.

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