A Stabilized Scintillation Crystal System for Monitoring Gamma Ray Exposure in the Environment

A 2 inch NaI(Tl) scintillator has been incorporated into a remote real time monitor for gamma ray background. The scintillator contains a small 241Am source which provides a high energy reference pulse for maintaining system gain. Gain is maintained automatically by a variable gain linear amplifier at the central station. The detector is connected to the central station by a single coaxial line which passes both the high voltage and the signal. Gamma ray pulses are processed in a modified Wilkinson analog to digital converter to provide an output count rate proportional to exposure rate (microR/hour). The system has been shown to be stable against temperature change, to be independent of gamma ray energy in the range 0.1 to 2.0 MeV, and to be useful in the range 1.0 to 10,000 microR/hour.