Shower-enabled on-orbit calibration algorithm for HERD 3D imaging calorimeter using high-energy cosmic-ray protons

The High Energy cosmic-Radiation Detection (HERD) facility is one of the space astronomy payloads planned for the China’s Space Station and will operate for over 10 years after its launch. The calorimeter (CALO) with high granularity for HERD consists of 7489 LYSO crystals, each measuring 3\times 3\times 3\ \text cm^3 . The on-orbit periodic calibration of these crystals is crucial for the decade-long operation and scientific detection of HERD. This paper investigates the possibility of selecting minimum ionizing crystals in proton shower events, and the shower-based calibration algorithm was therefore developed. By employing this algorithm, the shower events can be separated into two distinct processes: the minimum ionizing process and the shower process. The minimum ionizing process provides efficient crystal candidates for calibration of HERD CALO unit. In this paper, the shower-based calibration algorithm for proton events has been developed and evaluated using Monte Carlo simulations and validated using data obtained from HERD CALO prototype beam test conducted at CERN.