Beam test calibrations of the HEPD detector on board the China Seismo-Electromagnetic Satellite

CSES (China Seismo-Electromagnetic Satellite) is a Chinese-Italian space mission dedicated to monitoring of variations of the electromagnetic field and waves, plasma parameters, and particle fluxes induced by natural sources and artificial emitters in the near-Earth space. The satellite was launched from the Jiuquan Satellite Launch Center in the Gobi desert (Inner Mongolia, China) on 2, 2018. The expected mission lifetime amounts to 5 years. The Italian contribution to the mission includes the design and construction of the High-Energy Particle Detector (HEPD), aimed to detect electrons in the energy range between 3 and 100 MeV and protons between 30 and 200 MeV, as well as light nuclei in the MeV energy range. In this paper, we describe the calibration procedures applied to HEPD based on data acquired during two tests at accelerator laboratories, which were performed on HEPD Flight Model prior to the delivery to China for final integration. An additional acquisition of cosmic muons was performed in order to better characterize the detector response before launch.