Impact of crystal quality, geometry and surface finish for 3D impact position measurements in gamma ray detection systems

We have studied several ways of optimizing the 3D impact position measurements for gamma ray imaging detectors based on continuous monolithic large sized and thick scintillation crystals. The readout of such detectors is performed with position sensitive photo multipliers and with a depth of interaction (DOI) enhanced charge division readout. We have studied the effect of the crystal truncation angle, the reflective covering and the absorption and scattering mean free paths of the crystal. In particular, we have simulated and measured the impact on the energy resolution and the 3D spatial resolution. The results show that by optimization of the accessible crystal parameters we can enhance the performances with better resolution and less border compression. For truncated crystals we obtained an improvement of 60% in DOI and energy resolution in the borders and for the spatial resolution we appreciate also less compression in the borders.