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

A two-dimensional analysis of three coincident gamma-rays in (108)Ag(m) 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 (125)I was done recently for the case of two coincident gamma-rays in (60)Co decay (Volkovitsky and Naudus, 2009). A similar approach is applied to a more complicated case of three coincident gamma-rays in the (108)Ag(m) decay. The large number of experimental quantities, measured both in coincidence and anticoincidence modes, allows the determination of both detector efficiencies for all three gamma-ray photopeaks and to find the source activity. Results are compared with measurements of the activity of the same source with HPGe detectors.