Optical simulation and experimental measurement of gamma ray energy spectrum of plastic scintillators with different sizes

The application of large plastic scintillators is widely increasing in the different areas of industry, medicine and security due to technical and economic advantages. One of the main disadvantages of these detectors is the unknown position of Compton edge at gamma ray spectrum. In this research, GEANT4/GATE code has been used to simulate the gamma ray spectrum for different volumes of large plastic scintillator. According to these simulations, the dependence of the Compton edge position, energy resolution at Compton edge and efficiency of the optical photon collection to the scintillator dimensions has been investigated. The simulations showed that the Compton edge position with respect to local maximum at Compton continues strongly depends on the scintillator dimensions. These results were verified by experimental spectrometry.