High accuracy determination of the shape of the efficiency curve of the HPGe detector in the energy range 900 to 1300 keV

Abstract

A method for high accuracy characterization of the shape of a High Purity Germanium (HPGe) detector efficiency curve has been developed. Radionuclides with decay schemes having at least two [gamma] lines, for which the yield ratio can be calculated accurately, are used to establish the shape of the detector efficiency curve. Measurements using 60Co and 46Sc sources show that the behavior of the efficiency curve of the detector on a log-log scale is indistinguishable from that of a straight line with a slope of -0.828 +/- 0.004. Measurements using a 24Na source show that above 1368 keV this behavior no longer holds due to pair production and escape effects. The measured value of the slope in that case is -0.951 +/- 0.002. The proposed method is to be used in measurements requiring the minimum calibration bias in the determination of the reaction rate ratios, such as reactor dosimetry applications, integral cross section measurements and k0 determination for neutron activation analysis.