A prototype instrument was built for estimating dose rates to the skin. The detector is a planar diffused silicon photodiode used in a d.c. mode of operation. The response of that detector to beta-rays is similar to that of the thin (0.13 mm) Teflon TLD-100 discs. The lowest dose rate measurable is 1 rad/hr (0.01 Gy/hr) and the upper end of the scale is 20 krad/hr (200 Gy/hr). The characteristics of the instrument are given and some problems, that arise with non-biased surface barrier detectors, are discussed.
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