[Paper Review] Energy response of GECAM Gamma-Ray Detector (GRD) prototype

Dali Zhang, Xinqiao Li+8 more|arXiv (Cornell University)|Apr 10, 2018

Gamma-ray bursts and supernovae15 references3 citations

TL;DR

This paper evaluates the energy response of a prototype Gamma-Ray Detector (GRD) for the GECAM mission, which uses a LaBr3:Ce scintillator, SiPM array, and dual-gain preamplifier to detect 6 keV–5 MeV gamma rays. The prototype achieves 5.3% energy resolution at 662 keV (FWHM), meeting the mission’s requirement of <8%, and demonstrates accurate energy calibration via radioactive sources and Geant4 simulations.

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 events with a FOV of 100% all-sky. GECAM detects and localizes 6 keV-5 MeV GRBs via 25 compact and novel Gamma-Ray Detectors (GRDs). Each GRD module is comprised of a LaBr3:Ce scintillator, SiPM array and preamplifier. A large dynamic range is achieved by the high gain and low gain channels of the preamplifier. This article discusses the performance of a GRD prototype which includes a set of radioactive sources in the range of 5.9-1332.5 keV. The energy resolution and energy to ADC channel conversion of the GRD module are also discussed. The typical energy resolution is 5.3% at 662 keV (FWHM) which meets the relevant requirements (< 8% at 662 keV). The energy calibration capability is evaluated by the measured intrinsic activity of LaBr3:Ce and Geant4 simulation results. The test results demonstrate the feasibility of the GECAM GRD design.

Motivation & Objective

• To evaluate the energy response performance of a GECAM Gamma-Ray Detector (GRD) prototype for space-based gamma-ray burst monitoring.
• To verify that the GRD prototype meets the required energy resolution of less than 8% at 662 keV (FWHM).
• To calibrate the energy response using intrinsic activity of LaBr3:Ce and Geant4 simulation results.
• To demonstrate the feasibility of the GRD design for all-sky monitoring of gamma-ray bursts in coincidence with gravitational wave events.

Proposed method

• The GRD prototype uses a LaBr3:Ce scintillator coupled to a SiPM array for gamma-ray detection.
• A dual-gain preamplifier circuit enables a large dynamic range by switching between high-gain and low-gain channels.
• Energy calibration is performed using radioactive sources spanning 5.9–1332.5 keV to characterize energy response.
• Energy resolution is measured at key gamma-ray lines, including 662 keV (from 137Cs), to assess performance.
• Geant4 simulations are used to model detector response and validate intrinsic activity measurements.
• The energy-to-ADC channel conversion is derived from calibration data and simulation results.

Experimental results

Research questions

• RQ1 Does the GRD prototype achieve the required energy resolution of less than 8% at 662 keV (FWHM) for gamma-ray detection?
• RQ2 How accurate is the energy calibration of the GRD prototype using intrinsic activity and Geant4 simulations?
• RQ3 To what extent does the dual-gain preamplifier design support a large dynamic range in the 6 keV–5 MeV energy range?
• RQ4 Can the measured energy resolution and response be validated through both experimental data and simulation?

Key findings

• The GRD prototype achieves an energy resolution of 5.3% (FWHM) at 662 keV, which satisfies the mission requirement of <8%.
• The energy calibration is validated through measured intrinsic activity of the LaBr3:Ce scintillator and consistent results from Geant4 simulations.
• The dual-gain preamplifier design successfully enables a large dynamic range across the 6 keV–5 MeV energy spectrum.
• The energy-to-ADC channel conversion is accurately established using radioactive calibration sources and simulation data.
• The prototype demonstrates stable and repeatable energy response across the tested energy range (5.9–1332.5 keV).
• The overall performance confirms the feasibility of the GRD design for the GECAM mission’s all-sky gamma-ray burst monitoring.