Simulation method of performance of X-ray focusing mirror under actual surface state used in FXT on board EP satellite br

The Follow-up X-ray Telescope (FXT) is one of the main payloads on board the Einstein probe satellite. Inorder to obtain data with high signal-to-noise ratio and realize high-precision positioning of the sources, FXTadopts the Wolter-I X-ray focusing optical system which has been wildly used in X-ray astronomy. According tothe principle of Wolter-I and combining the actual manufacture characteristics, we simulate several keyparameters affecting the optical quality by Monte Carlo simulation algorithm, such as surface roughness Root-Mean Square (RMS) and surface profile error. The effect of each parameter is analyzed according to thesimulation results. Then, the simulation method is verified by the test results of the focusing mirrors providedby PANTER laboratory, and the surface profile error parameters are restricted. The simulation results of thehalf energy width of the structural-thermal module mirror are basically consistent with the test results. Thismethod can be effectively applied to the later study of focusing mirror manufacture and can accumulateexperience for testing and calibrating FXT focusing mirrors. Furthermore, combining the tested calibrationdata, some key performance of the mirrors can be obtained by this simulation method, such as the effectivearea, vignetting and the point spread function, which can compose the on-orbit calibration database