Development of a compact mercuric iodide radiation intensity counter

Constellation Technology Corporation has developed a pocket-sized radiation intensity counter (RIC) for monitoring ambient radiation levels, search activities, and customs inspection. The RIC incorporates a sensitive 2.5 cm×2.5 cm×0.5 cm mercuric iodide (HgI2) detector operating at room temperature. The instrument provides the user with a visual indication of the gamma-ray count-rate by means of a 7 segment bargraph scale arranged in a semi-logarithmic scale. An alarm alerts the user when the count rate exceeds a pre-selected level. Power is supplied by two commonly available AA alkaline batteries. Total power consumption <2 mW and the battery life is estimated to be >3 months under continuous use. The design of the RIC is described in detail and results of testing sensitivity, positional response, power consumption, and temperature stability are presented.