Simulation method of Wolter type I grazing incidence telescope imaging of an X-ray region

Abstract

This paper presents a method for simulating Wolter type I grazing incidence telescope imaging of an X-ray region. The imaging quality of a soft X-ray telescope is mainly affected by geometric aberrations, surface scatter and alignment errors. Using a Legendre-Fourier polynomial to fit the figure errors in the cylindrical coordinate system, the geometry of the mirror barrel with the figure errors can be modeled by the User Defined Object in ZEMAX. Based on the Harvey-Shack surface scatter theory, surface scatter is achieved by the Bidirectional Scatter Distribution Function (BSDF) scattering model. The alignment errors are calculated by a combination of experiment and simulation according to the shape of the spot resulting from the finite distance imaging experiment. By combining these factors that affect image quality, the telescope imaging of an infinity point is simulated by ZEMAX. According to the simulation results, the angular resolution of the telescope is calculated to be less than or equal to 1.86′ at a wavelength of 1.33 nm. The simulation method improves the ability of ZEMAX to simulate grazing incidence telescope imaging. This is of great significance for the research and manufacture of X-ray grazing incidence telescopes.