Simple technique for precise determinations of counting losses in nuclear pulse processing systems

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A new technique has been developed to determine precisely the fraction of all counting losses suffered in counting and pulse height analysis systems. Of particular significance is the applicability of this method to time-dependent counting rates. The method is based on a technique in which the rate of radiation incident upon the detector is sampled continually. Upon the detection of a preset number of counts, a pulser signal is injected into the preamplifier. At the end of the experiment, the total number of injected pulses is compared with the number of these pulses that are recorded in the multichannel analyzer or scaler. Since the pulser peak suffers the same fractional losses as the spectral components of the detected nuclear events, such a comparison provides an accurate representation of the counting losses due to all loss-producing effects. These include losses incurred in ADCs, computers, pileup rejectors, etc. Losses suffered due to pileup may not be negligible compared with those due to the ADC and memory of fast multichannel analyzers. The application of this technique to constant counting rates, and to varying counting rates encountered in charged-particle-induced reactions and in radioactive-decay studies are treated in detail.