Dedicated SiPM Array for GRD of GECAM

The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy. With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts, the gravitational wave high-energy electromagnetic counterpart all-sky monitor (GECAM) possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent observations. Each satellite of GECAM was fitted with 25 3-inch-diameter gamma-ray detectors (GRD), covering an energy range of 8–2 MeV. GRDs have adopted silicon photomultiplier tubes (SiPM) in lieu of photomultiplier tubes (PMT) to adapt to the dimensional limitations of micro-satellites. A unique 3-inch circular SiPM array was designed. In this design, 64 6 × 6 mm chips were arranged evenly in a circular manner with the seams filled with reflecting films, thus achieving satisfactory uniformity of light collection. The integrated pre-amplifier circuit on the back of the SiPM array adopted two-level grouping and summing; further, it achieved a satisfactory signal-to-noise ratio. Two high-gain and low-gain channels were adopted to achieve a large dynamic range, and two independent power supply units were used, where each unit can be closed separately, thus improving reliability. Performance studies show that this SiPM array meets the requirements of GECAM. A 3-inch SiPM array have been developed that uses grouped summation, reflective films, a circular arrangement, two groups of independent power supplies, high- and low-gain signals, differential signal output technologies, etc. This solution can be used not only for GECAM, but also as a general solution for SiPM-based scintillation detectors.