The HEPD detector on board CSES satellite: in-flight performance

In this paper we will present a description of the High Energy Particle Detector (HEPD) onboard the China Seismo Electromagnetic Satellite (CSES) and its (preliminary) performance in flight. CSES mission aims at monitoring electromagnetic field, plasma and particles perturbations of atmosphere and inner Van Allen belts caused by solar and terrestrial phenomena and to the study of the low energy component of the cosmic rays. The satellite was launched from the Jiuquan Satellite Launch Center located in west of inner Mongolia on February 2nd, 2018 and is now orbiting in nominal condition. It hosts several instruments onboard: two magnetometers, an electrical field detector, a plasma analyser, a Langmuir probe and two particle detectors. The high energy particle detector (HEPD), designed and built by the Italian Limadou collaboration, is able to separate electrons and protons and identify nuclei up to Iron. HEPD provides good energy resolution and high angular resolution for electrons (3-100 MeV) and proton (30-200 MeV). The instrument consists of: 2 planes of double-side silicon microstrip sensors placed on the top of the instrument (direction of particle); 2 two layers of plastic scintillators (trigger) and a calorimeter (constituted by other 16 scintillators and a layer of LYSO sensors). A scintillator veto system completes the instrument. The commissioning of the HEPD and the other instruments on board was successfully completed in July 2018.