基本信息
摘要：685,027. Radiation-sensitive devices; measuring X-rays. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Oct. 11, 1951 [Oct. 18, 1950], No. 23729/51. Class 40 (iii). - A semi-conductor device which varies in conductivity on the incidence of X-rays comprises a crystal of cadmium sulphide with a steady polarizing voltage. The crystal should be free from lattice distortion, e.g. it should have been annealed in an oxygen-free atmosphere. A sensitive device may comprise a stack or row of crystals with their negative ends presented to the X-rays. To increase the sensitivity, the crystal is steadily illuminated, preferably with green light of 5200 A.U. wavelength. Such illumination also reduces the duration and intensity of the surge of current when X-rays are suddenly applied to the crystal. This surge effect is increased by red light and eliminated by blue light. Where the X-rays are pulsating, an A.C. amplifier 15 can be used to operate the indicator or meter and no compensation is necessary in respect of the steady illumination by source 21. The apparatus may be used for giving a warning of the presence of X-rays, for controlling their intensity or dosage, for indicating liquid levels and for detecting foreign bodies in food packets.
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