Improvements of the standardization of 134Cs by the critical window setting for 605Â keV photopeak

In the standardization of 134Cs by the 4πβ−γ coincidence method with a γ-window at 605 keV, the satellite components of 563 keV and 569 keV overlapping the 605 keV peak cause a steep slope and non-linearity of the efficiency extrapolation function. By shifting the lower threshold of a γ-window higher, the satellite components are eliminated, and the slope tends to horizontal. Nearly flat efficiency curves were obtained by using a CeBr3 scintillator for detecting γ-photons, as well as a NaI(Tl) scintillator.