The Response of p-i-n Junctions to Beta Rays II. Count Rate Versus Surface Absorbed Dose Rate for Phosphorus-32 and Thallium-204

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Abstract
The use of Li drifted Si p-i-n [positive-intrinsic-negative semi-conductor diode] junctions as pulse counters for [beta]-ray dosimetry was investigated using the [beta]-rays emitted by 32p and 204Tl. The counting rate is directly compared with the surface absorbed dose rate as measured at the polystyrene electrode of a thin window extrapolation chamber. The rate of change of the detector response is compared with the rate of change of absorbed dose rate as a function of source-to-detector distance, source geometry and detector area. The ratio of these quantities remains constant after a certain minimum source-to-detector distance is achieved. In all cases investigated this distance did not exceed 10 cm. The absolute sensitivity of these devices is such that dose rates as low as 0.1 mrad/hr. can be measured.