Study of a small-scale gamma-ray detection system employing Compton scattering with a monolithic CeBr3 crystal and segmented photodetector array

TL;DR

This work addresses the challenge of efficient MeV gamma-ray detection by exploring a compact two-plane Compton telescope built from CeBr3 scintillators read out by SiPM arrays. A Geant4-based Monte Carlo study assesses energy deposition and detection efficiency for Cs-137 gamma rays at 662 keV with plane separations of 5 cm and 10 cm, highlighting three interaction populations and the superior performance of 180$^\circ$ backscatter events for energy and timing. The study reports energy-conserving events ($E=E_1+E_2$) for the first two populations, an efficiency of roughly $\varepsilon \approx 0.40$–$0.45$ and solid angles of $\Omega \approx 1$ sr and $0.25$ sr, respectively, indicating how plane distance affects imaging capability and throughput. The modular hardware, including 3D-printed components and commercial readout chains, positions the setup for validation with a gamma source and demonstrates potential for a small-scale, nanosatellite-compatible Compton telescope with CeBr3-based detectors. All mathematical relations are presented with proper notation to support reproducibility and integration into imaging analyses.

Abstract

Study of high energy cosmic events in the MeV range requires detector with high efficiency and energy resolution to be constructed. The present setup consisting of scintillator crystals CeBr3 with different thickness, each coupled with 12 x 12 segmented SiPM-based photodetector in a multichannel system represents an initial exploration of a gamma imaging system based on Compton scattering principles. A Monte Carlo simulation was conducted to evaluate the energy deposit and detection efficiency using the 137Cs gamma line. The study reveals a correlation between the relative distance between detector planes and the energy deposition efficiency, providing valuable insights into optimizing the telescope design.

Figures (5)

• Figure 1: A schematic representation of the experimental setup.
• Figure 2: A picture of the assembled test Compton telescope.
• Figure 3: A scheme of the full experimental setup - Compton telescope and the two readout systems responsible for the operation of the two ends of the telescope.
• Figure 4: Distribution of the energy deposit in the front (left) and in the back end (right) scintillator for 5 cm (top) and 10 cm (bottom) distance between the scintillators.
• Figure 5: $E_1$ vs $E_2$ for the two relative relative distance 5 cm (left) and 10cm (right)