THE USE OF SOURCES EMITTING COINCIDENT GAMMA-RAYS FOR THE DETERMINATION OF PHOTOPEAK AND TOTAL EFFICIENCIES IN NON-POINT-SOURCE COUNTING GEOMETRIES

The validity of a previously published method for determination of ful l-energy peak as well as total efficiency curves and source activity f rom a Br-82 spectrum is experimentally tested for the case of a thin s lab counted on the end cap of a 20% relative efficiency HpGe detector, as well as for a Marinelli beaker geometry. It is concluded that, eve n though a full-energy and total efficiency curve can be found that re produce the measured Br-82 spectrum, the corresponding source activity is an underestimation of the true value, apparently depending on the degree of variation of the efficiencies over the source volume. The ap plicability of the curves found to other radionuclides is as yet uncle ar.