energy of the detected photons, and may cause two neighboring energypeaks to overlap. Interference between neighboring peaks can result insome uncertainty in determining the activity at a particular energy. Becauseof these factors, if possible, a standard sample of the same volume,and known concentration, of the element of interest should be irradiatedat the same time as the inspected sample. The same measurement procedureshould also be used simultaneously for both the standard andthe test sample. This relative (or comparator) method of measurementeliminates the need to explicitly determine any of the factors includedin Eq. (8.4), and enables direct measurement of the unknown concentration,with respect to that of the standard sample, using the ratiobetween the measured activities.
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