The Origin of Summing

As with random summing, the event results in loss of counts from the full-energy gamma-ray peaks and a loss of efficiency. However, unlike the random summing that I discussed in Section 4.8, the summed pulse will not be misshapen and cannot be rejected by pile-up rejection circuitry. 

A rough and ready estimate of the likelihood of summing of two photons emitted at the same time, P, can be estimated by using the following equation  

Since every de-excitation of Sm, whatever gamma-rays are emitted, is likely to produce an X-ray these play a 

A further possibihty that I perhaps ought to mention is that in the case of beta decay, because the beta particle and the de-excitation gamma-rays are emitted almost 

1 Efficiency calibration using QCYK mixed nuclide sources 

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