Analyze Methodology of ToF Spectrum on Cherenkov and Scintillation Emission in BGO Scintillator

Abstract

A time-of-flight (ToF) spectrum model has been developed to quantitatively understand the emission sequences in realistic scintillation detectors. This model is used to carefully investigate the Cherenkov and scintillation photon emission processes. To construct this model, we initially identified several primary physical processes occurring within scintillators and selected those that significantly contribute to the spectrum. The characteristics of each process were statistically incorporated into the model. Importantly, the model also takes into account the variance in the interaction point between the incident gamma photon and the electron, which serves as a contributing factor. To confirm the model’s validity, an experiment was conducted. A pair of 20-mm long bismuth germanate oxide detectors, paired with a silicon photomultiplier, used for this purpose. Experimental results provided the number of scintillation photons and the scintillation decay time constants. The time constant for Cherenkov emission was derived from the existing literature, and approximately one Cherenkov photon was used to fit the ToF spectrum obtained by the experiment. The model successfully reproduced the experimental ToF spectra with validity using the parameter values obtained in the experiment. However, the estimated number of scintillation photons in our experiment was about half of the yield number reported in literatures, while the number of Cherenkov photons utilized in the validation process was in line with those reported by other groups. Our results suggest that a combined analysis of the phenomenological model that accepts the behavior of the real system and particle-based Monte-Carlo simulation that treats the ideal system deductively is a meaningful approach for detector development based on an accurate understanding of the real system.