Pixellated NaI (Tl) Detector for Light Yield Nonproportionality Investigation

An 8 × 8 pixellated Nal(Tl) detector (1.7 cm × 1.7 cm × 1.0 cm) coupled to a multi anode PMT read out system was modeled to study the impact of light yield nonproportionality due to multiple photon scatterings and assess the contribution of delta rays in Nal(Tl) energy resolution. Geant4 simulation tool with modified nonproportional optical photons sampling routine was used in the study. A deconvolution technique was implemented to allow decoupling of the multiple photon scatterings contribution from the total energy resolution. Results from the simulation demonstrated that the effect of nonproportionality due to multiple photon scatterings is too small to be observed. However, the contribution of the delta rays was found to be a significant component of the evaluated Nal(Tl) energy resolution.