We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and non-linear dependences on the deposited energy. In this approach, the scintillation response is described as a function of the deposited energy deposition and the kinetic rates of each relaxation channel. This mathematical framework allows both a qualitative interpretation and a quantitative fitting representation of scintillation non-proportionality response as function of kinetic rates. This method was successfully applied to thallium doped sodium iodide measured with SLYNCI, a new facility using the Compton coincidence technique. Finally, attention is given to the physical meaning of the dominant relaxation channels, and to the potential causes responsible for the scintillation non-proportionality. We find that thallium doped sodium iodide behaves as if non-proportionality is due to competition between radiative recombinations and non-radiative Auger processes. � 2006 IEEE.
BIZARRI, G., CHEREBY, N., CHOONG, W., HULL, G., Moses, W., Singh, J., VALENTINE, J., VASILEV, A., & Williams, R. T. (2009). Progress in Studying Scintillator Proportionality: Phenomenological Model. IEEE Transactions on Nuclear Science, 56, 2313-2320. https://doi.org/10.1109/TNS.2009.2022625