Calculation for the Space Environment Background of HXMT

The Hard X-ray Modulation Telescope (HXMT) is a broadband X-ray (1∼250 keV) astronomical satellite. Its core payload, the High Energy X-ray Telescope (hereafter HE), is operated in the hard X-ray energy range (20∼250 keV) and dedicated to the hard X-ray high-sensitivity survey observation, hard X-ray sky mapping and high-sensitivity focused observations towards particular celestial bodies. In order to achieve a high sensitivity, it is important to reduce effectively the background that is caused by the interactions between the detector and space particles (γ-ray, protons, electrons, neutrons). Combining a series of references about the near-earth space background with the up-to-date observational data, this paper presents a set of self-consistent data and energy spectrum formulae of near-earth space particles for the convenience of applications. In addition, by the simulative calculations with the software Geant 4, the background of HXMT and its variations with the time and orbit are also given.