Extended range radiation dose-rate monitor

Claim 1

An extended range counter system for measuring ionizing radiation dose-rates up to at least 1000 R/h, comprising: an ionizing radiation detector means for producing current pulses at a rate corresponding to the photon interaction rate of ionizing radiation to be detected and having an amplitude proportional to the charge deposited by each photon of radiation detected; an amplifier means responsive to each of said current pulses for generating fixed width voltage pulses at an output thereof having an amplitude proportional to the amplitude of said current pulses; a comparator means having a signal input connected to the output of said amplifier means and a reference voltage input for generating a logic pulses at an output thereof for each input pulse from said amplifier means which exceeds the comparator means threshold determined by a reference voltage level applied to said reference voltage input of said comparator means; an integrator means connected to the output of said comparator means for integrating said logic pulses to provide an output signal proportional to the rate of logic pulses applied to the input thereof; a signal feedback means for feeding back a selected portion of the output signal from said integrator means to said reference voltage input of said comparator means to vary the comparator means threshold so that as the radiation dose-rate detected by said detector means increases the comparator means threshold increases to extend the sensitive dynamic range of the system up to at least 1000 R/h; and a meter connected to the output of said integrator means and calibrated to indicate measured radiation dose-rate in response to the output signal of said integrator means.