The design of a liquid scintillation counter based on the triple to double coincidence ratio method

In Liquid Scintillation Counting (LSC), the Triple to Double Coincidence Ratio method (TDCR) is an absolute activity measurement method, especially developed for pure β- and pure EC-emitters activity standardisation. In this method, the detection efficiency is calculated using a physical and statistical model of the photon distribution emitted by the source. The application of this method requires the use of a specific three-photodetector Liquid Scintillation (LS) counter, which is not commercially available. When designing such a counter, the fundamental basis of the LSC phenomena and TDCR method must be taken into account. The key points of this design are presented in this paper.