Energy response and in-flight background simulationfor GECAM

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is designed to detect gravitational wave gamma-ray bursts and other high-energy transient sources in the energy range of 6 keV-5 MeV. It has the characteristics of all-sky field of view, high sensitivity, good positioning accuracy and wide band coverage. The mission consists of two satellites with each containing 25 gamma-ray detectors (GRD) and 8 charged particle detectors. In this paper, the energy response matrix and in-flight background of each GECAM detector are obtained by Geant4 simulation. The simulation results show that the GECAM has stronger observation ability than the Fermi/GBM in low-energy range. The average in-flight background of a single GRD is about 800 cps, and there are three characteristic peaks that can be used for on-orbit calibration.