Monte Carlo simulation of a plastic scintillator response function in β–γ coincidence measurement

A β–γ coincidence spectrometer consisting of a 2π plastic beta detector and a NaI(Tl) detector, is described. In order to evaluate performance of the spectrometer, Monte Carlo simulation of the plastic and NaI(Tl) scintillators responses has been performed using GEANT4 code. This study reveals the possible efficiency loss of the system and enables us to calculate gamma detection efficiency of the system for different source-detector geometries.