The Einstein Probe mission that will be launched in 2022, is dedicated to time-domain high-energy astrophysics. Its primary goals are to discover high-energy transients and to monitor variable objects in 0.5-4 keV energy band. To realize these objectives, EP is equipped with a Wide-filed X-ray Telescope (WXT) which applies the micro-pore optics (MPO). Background is critical for a space X-ray instrument, since it is related to sensitivity and observation data quality. In this work, we study the background components of WXT induced by cosmic X rays, soft X rays from the Galaxy based on ray tracing program. We also investigate the background due to energetic cosmic rays, the count rate of which varies with the thickness of detector sensitive layer. Furthermore, we simulate the contribution of low-energy electrons to the background of WXT, which would degrade the sensitivity notably without electron diverters. The electron diverters for WXT are under development based on simulations.
The Einstein Probe (EP) is a small satellite dedicated to time-domain astronomy to monitor the sky in the soft X-ray band. It is a mission led by the Chinese Academy of Sciences and developed in its space science programme with international collaboration. Its wide-field imaging capability is achieved by using established technology of the micro-pore lobster-eye X-ray focusing optics. Complementary to this is deep X-ray follow-up capability enabled by a Wolter-I type X-ray telescope. EP is also capable of fast transient alerts triggering and downlink, aiming at multi-wavelength follow-up observations by the world-wide community. EP will enable systematic survey and characterisation of high-energy transients at unprecedented sensitivity, spatial resolution, grasp and monitoring cadence. Its scientific goals are mainly concerned with discovering new or rare types of transients, including tidal disruption events, supernova shock breakouts, high-redshift GRBs, and of particular interest, electromagnetic sources of gravitational wave events.
Einstein Probe (EP) is a proposed small scientific satellite dedicated to time-domain astrophysics working in the soft X-ray band. It will discover transients and monitor variable objects in 0.5-4 keV, for which it will employ a very large instantaneous field-of-view (60° × 60°), along with moderate spatial resolution (FWHM ∼ 5 arcmin). Its wide-field imaging capability will be achieved by using established technology in novel lobster-eye optics. In this paper, we present Monte-Carlo simulations for the focusing capabilities of EP’s Wide-field X-ray Telescope (WXT). The simulations are performed using Geant4 with an X-ray tracer which was developed by cosine (http://cosine.nl/) to trace X-rays. Our work is the first step toward building a comprehensive model with which the design of the X-ray optics and the ultimate sensitivity of the instrument can be optimized by simulating the X-ray tracing and radiation environment of the system, including the focal plane detector and the shielding at the same time.