Solid state semiconductor detectorized pocket alarm dosimeter

Equipped with a special semiconductor detector, the pocket alarm dosimeter newly developed by the authors achieves a long life and can be used for a wide measuring range, 80 KeV - 6 MeV, compared to conventional units. The detector unit consists of an preamplifier and a semiconductor detecting device. A space-charge region is generated when a bias voltage is applied to the electrodes of the detector, which provides a depletion layer. If radioactive rays get into the layer, hole-electron pairs are produced due to the ionization effect and the electrons and holes will move toward the anode and cathode, respectively, resulting in the generation of electric charge pulses in the external circuit. The pulses are amplified and pulse-height discrimination is carried out. The circuit is controlled by a one-chip microcomputer and data input and output are performed using an optical system. Special accessories are also available, including charger, presetter and read checker. An indivisual exposure monitoring system using this dosimeter is also presented. (Nogami, K.)