Energy Response of GECAM Gamma-Ray Detector Based on LaBr3:Ce and SiPM Array

TL;DR

This paper evaluates the energy response of GECAM's gamma-ray detector prototype, based on LaBr3:Ce scintillator and SiPM array, demonstrating its suitability for detecting gamma-ray bursts in space with high resolution and calibration capabilities.

Contribution

The study presents the design, energy response evaluation, and calibration methods for GECAM's novel gamma-ray detector using LaBr3:Ce and SiPM, advancing space-based gamma-ray detection technology.

Findings

Energy resolution of 5.3% at 662 keV meets requirements.

Effective nonlinearity correction reduces residuals below 1.5%.

Simulated background and intrinsic activity support in-flight calibration feasibility.

Abstract

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) , composed of two small satellites, is a new mission to monitor the Gamma-Ray Bursts (GRBs) coincident with Gravitational Wave (GW) events with a FOV of 100% all-sky.Each GECAM satellite detects and localizes GRBs using 25 compact and novel Gamma-Ray Detectors (GRDs) in 6 keV-5 MeV. Each GRD module is comprised of LaBr3:Ce scintillator, SiPM array and preamplifier. A large dynamic range of GRD is achieved by the high gain and low gain channels of the preamplifier. The energy response of GRD prototype was evaluated using radioactive sources in the range of 5.9-1332.5 keV. A energy resolution of 5.3% at 662 keV was determined from the 137Cs pulse height spectra, which meets the GECAM requirement (< 8% at 662 keV). Energy to channel conversion was evaluated and a nonlinearity correction was performed to reduce the residuals (< 1.5%). Also, a Geant4-based simulated in-flight background and a measured GRD LaBr3:Ce intrinsic activity were used to evaluate the capability of in-flight calibration. These results demonstrate the design of GRD.