DETECTOR SIMULATION FOR RADIATION MONITORING SYSTEMS

Abstract

In the work, a model of primary transducer - gamma radiation sensor has been created. It is based on the following properties of a semiconductor crystal: maximum quantum efficiency; maximum mobility of charge carriers; minimum density of structural defects; maximum values of resistivity and density. The combination of these properties provides significant sensor sensitivity with a minimum crystal size. The inconsistency of this combination must be eliminated both in the process of crystal fabrication (for example, a high-resistance crystal is obtained by the simultaneous use of purification, components, and compensating doping) and subsequent processing by the methods proposed in this work (thermal field method, ionization annealing). To register small signals, it is necessary to have minimal loss currents at sufficiently high voltages applied to the sensor. This means that the semiconductor material must be highly resistive. Among the known materials for gamma radiation sensors, single crystals of CdxZn1-xTe solid solutions have an optimal combination of the properties listed above and the possibilities of their production. The creation of a model gamma-radiation detector as a single system of primary and secondary converters is considered. It contains physical analysis and analytical presentation of processes occurring in CdZnTe-sensor and electronic preamplifier. It is shown that the charge collection in the sensor differs in time, which leads to a spread of signal pulses in duration and amplitude. In this regard, the model shows need to use a charge-sensitive preamplifier.