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A method has been developed to automatically correct for the dead time losses in a 4Â¿Ã and 4Â¿Ã-Â¿ coincidence calibration facility. Since radioactive disintegrations occur at random in a manner described by the Poisson distribution, the probability of observing exactly "0" counts in an interval in which the average number of counts is "vT', is: Po = e-vT. By measuring "Po" in the interval "T", the true counting rate "v" can be calculated. This counting rate, as thus determined, is independent of any model for dead time behavior of the detector and substantially independent of secondary pulses. A simple three-channel instrument which measures "Po" is described. This analysis is applied to Geiger, proportional, and scintillation detectors. Comparison of the true counting rate from this analysis to the conventional output can be used as a simple, accurate determination of resolving time.
Date of Publication: Feb. 1966