Absolute 108Agm characterization based on gamma-gamma coincident detection by two NaI(Tl) detectors

A two-dimensional analysis of three coincident γ-rays in 108Agm decay, detected by two NaI(Tl) scintillation detectors, allows a direct measurement of the source activity. A modification of the Eldridge-Crowther formulas derived originally for 125I was done recently for the case of two coincident γ-rays in 60Co decay (Volkovitsky and Naudus, 2009). A similar approach is applied to a more complicated case of three coincident γ-rays in the 108Agm decay. The large number of experimental quantities, measured both in coincidence and anticoincidence modes, allows the determination of both detector efficiencies for all three γ-ray photopeaks and to find the source activity. Results are compared with measurements of the activity of the same source with HPGe detectors.