207Bi characterization by gamma–gamma coincident detection

A two-dimensional analysis of γ rays emitted in coincidence in 207Bi decay and detected by two NaI(Tl) scintillation detectors allows a direct measurement of the source activity. A modification of Eldridge–Crowther formulas, derived originally for 125I, was made recently for the case of two coincidence γ-rays in 60Co decay (P. Volkovitsky and P. Naudus (2009) [10]) and for the 108Agm decay with three coincidence γ-rays (P. Volkovitsky (2010) [14]). A similar approach is applied to a more complicated decay scheme with two decay modes with coincidence γ rays in the 207Bi decay. The large number of experimental quantities, measured both in coincidence and anti-coincidence modes, allows determination of both detector efficiencies for γ rays together with the source activity. Results are compared with measurements of the source activities performed with HPGe detectors.