GEANT4 studies on the propagation and detection of scintillation light in long thin YAP crystals

The response to γ-rays of long thin polished or wrapped YAP:Ce scintillator bars read out at both edges by photomultipliers has been studied by means of GEANT4 simulations with the aim to investigate the capability of the charge division method to reconstruct the gamma interaction point in the crystal. The GEANT4 simulations took into account the optical properties of the scintillator like absorption, reflection, and diffusion during the passage of the light through the crystal. The simulations were able to reproduce experimental measurements of light yields in polished and wrapped YAP:Ce crystals with dimensions 3.2×3.2×100 mm3. Once validated, the simulations could show that a particular patterning of the crystal surface, which enhances the surface absorption, should lead to a significant improvement of the reconstruction precision of the charge division method, without compromising the energy resolution.