Physics of scintillator nonproportionality

Scintillator nonproportionality is a key mechanism by which the energy resolution is degraded in gamma spectroscopy. Herein, we survey the results obtained for a number of inorganic scintillating materials, including alkali and multivalent halides, fluorides, simple oxides, silicates, and a tungstate. The results are interpreted in the context of a model that accounts for carrier attraction by the Onsager mechanism and exciton-exciton annihilation by the Birks model. We then utilize the theory of Landau fluctuations in combination with the fitted experimental nonproportionality curves to deduce the predicted value of the resolution degradation.