Determination of quench curve and evaluation of accuracy of counting on liquid scintillation counter

Liquid scintillation process is conversion of the energy of radioactive decay into photons. The conversion efficiency depends on the sample conditions such as existence of a quencher and color of the sample. To determine the activity of an unknown sample by using a liquid scintillation counter, the conversion efficiency must be accurately determined. The conversion efficiency for two liquid scintillation counters, which is called a quench curve, was measured using two series of tritium standard samples. Accurate quench curves for both counters were obtained. The quench curves differed from each other because the energy window of tritium on multi-channel analyzers differed. The characteristics of the quench curves were essentially similar to each counter systems. The quench curves indicated that the accuracy of counting decreased with strengthening of quenching for both liquid scintillation counters. On the other hand, the quench curves were independent of the activity of tritium. (author)