Automatic Gain Control for Radiation Detection Systems

A simple automatic control system capable of compensating for detector gain changes over a dynamic range of 10 has been developed for laboratory and aerospace radiation detection systems. The basic concept involves a feedback system that adjusts the system gain to keep the peak of a stable calibration source at a predetermined level. Two variations are described, one providing continuous calibration and the other calibrating on command. The effects of calibration source characteristics and critical circuit parameters on the total system accuracy are discussed. Typical results for a proportional counter X-ray spectrometer indicate that the system gain can be maintained to within 4 percent of its initial value for a detector gain degradation of a factor of 3.