Simulation of Electron-Hole Pairs Created by γ-Rays Interaction in Scintillation Crystals Using Geant4 Toolkit

Understanding the electron-hole pair (e-h pair) production process in scintillators is essential for further studies of the scintillation mechanism. The number of e-h pairs can be derived from theoretical and empirical approaches. However, simulation approaches have been chosen to study all the related physical processes and spatial information in scintillation crystals. Due to the complexity of particle interaction and physical properties of solid-state, the simulation approach could be better than the analytical approach. This work aims to develop a Geant4-based simulation toolkit for studying scintillation mechanisms in single-crystalline scintillators since Geant4 can accurately calculate particle energy loss. Due to the lack of a solid-state physics model for insulators, the plasmon creation and phonon loss process for electrons are implemented in the Geant4 toolkit. The electrons, which are created by rays interaction in crystals, can make further ionization to generate secondary electrons or create plasmons, or lose energy to phonons. Then the created plasmons decay into e-h pairs. These electrons and holes are tracked with information on energy and position. Therefore, the number of created e-h pairs and their spatial distribution can be extracted. In this work, we will present the result of the creation process of e-h pairs per MeV in scintillation crystals induced by rays interaction. The number of e-h pairs created by ray in some popular inorganic crystals has been calculated. Assuming maximum conversion efficiency from the e-h pair to the luminescence light, we can calculate the maximum light yield of the intrinsic scintillator.