The Coincidence Readout of SiPM-based detector of DRO/GTM (GECAM-D): Design And Ground Test

As a new member (denoted as GECAM-D) of the Gravitational Wave Electromagnetic Counterpart All-sky Monitor (GECAM) constellation, the Gamma-ray Transient Monitor (GTM) on the DRO-A satellite is primarily designed to detect gamma-ray transients from 15 keV to 1 MeV, such as Gamma-Ray Bursts (GRBs), the high energy counterparts of Gravitational Waves (GWs) and Fast Radio Bursts (FRBs), and Soft Gamma-ray Repeaters (SGRs). DRO/GTM can also monitor the solar activities and environmental radiation of the DRO orbit. Although the SiPM-based gamma-ray detector has been successfully employed in GECAM, the issue of SiPM dark noise caused by irradiation needs further improvement. For DRO/GTM, a novel coincidence readout is proposed and implemented for the SiPM-based detector, which reduces dark noise by several orders of magnitude. This paper primarily introduces the design and ground test results.