Dependence of the energy resolution of a scintillating crystal on the readout integration time

TL;DR

This paper investigates how the energy resolution of a scintillating crystal detector depends on the readout integration time, highlighting the impact of statistical fluctuations and the benefits of optimized measurement strategies.

Contribution

It provides experimental and simulation-based analysis of the relationship between integration time and energy resolution in slow scintillators, introducing a model for predicting performance.

Findings

Energy resolution is driven by photoelectron fluctuations.

Fluctuations are smaller than Poisson predictions at low photoelectron counts.

Monte Carlo simulation effectively estimates energy resolution based on key parameters.

Abstract

The possibilty of performing high-rate calorimetry with a slow scintillator crystal is studied. In this experimental situation, to avoid pulse pile-up, it can be necessary to base the energy measurement on only a fraction of the emitted light, thus spoiling the energy resolution. This effect was experimentally studied with a BGO crystal and a photomultiplier followed by an integrator, by measuring the peak amplitude of the signals. The experimental data show that the energy resolution is exclusively due to the statistical fluctuations of the number of photoelectrons contributing to the peak amplitude. When such number is small its fluctuations are even smaller than those predicted by Poisson statistics. These results were confirmed by a Monte Carlo simulation which allows to estimate, in a general case, the energy resolution, given the total number of photoelectrons, the scintillation time and the integration time.