Geant4 Modeling of a Cerium Bromide Scintillator Detector for the IMPRESS CubeSat Mission

TL;DR

This paper models a cerium bromide scintillator detector for the IMPRESS CubeSat mission using Geant4 Monte Carlo simulations, validating the model against experimental data and addressing energy resolution and light collection issues.

Contribution

It presents a validated Geant4 Monte Carlo model of the scintillator detector, improving understanding of detector response for space-based solar flare observations.

Findings

Geant4 model aligns with analytical calculations.

Simulations explain experimental features but not full energy resolution.

Nonuniform light collection causes double-peak behavior, correctable in models.

Abstract

Solar flares are some of the most energetic events in the solar system and can be studied to investigate the physics of plasmas and stellar processes. One interesting aspect of solar flares is the presence of accelerated (nonthermal) particles, whose signatures appear in solar flare hard X-ray emissions. Debate has been ongoing since the early days of the space age as to how these particles are accelerated, and one way to probe relevant acceleration mechanisms is by investigating short-timescale (tens of milliseconds) variations in solar flare hard X-ray flux. The Impulsive Phase Rapid Energetic Solar Spectrometer (IMPRESS) CubeSat mission aims to measure these fast hard X-ray variations. In order to produce the best possible science data from this mission, we characterize the IMPRESS scintillator detectors using Geant4 Monte Carlo models. We show that the Geant4 Monte Carlo detector model is consistent with an analytical model. We find that Geant4 simulations of X-ray and optical interactions explain observed features in experimental data, but do not completely account for our measured energy resolution. We further show that nonuniform light collection leads to double-peak behavior at the 662 keV $^{137}$Cs photopeak and can be corrected in Geant4 models and likely in the lab.