Particle contamination simulation of Einstein probe follow-up X-ray telescope focusing mirror

Abstract

Particle contamination can greatly affect the performance of X-ray focusing mirror. In this paper, we analyze the influence of particle contamination on X-ray focusing mirror. The model of interaction between contaminant particles and incident light is established from Mie scattering theory in the wavelength range of X-ray. And the relationship between them is mainly influenced by the complex refractive index of the particles <inline-formula><tex-math id="M1">\begin{document}$m$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230301_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230301_M1.png"/></alternatives></inline-formula> and the scale factor <inline-formula><tex-math id="M2">\begin{document}$\alpha$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230301_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20230301_M2.png"/></alternatives></inline-formula>. Therefore, the reaction cross section and scattering function of particle contamination are calculated. Then, in order to obtain the effect of particle contamination on Einstein probe follow-up X-ray telescope (EP-FXT) focusing mirror, we carry out Monte Carlo simulation based on the design parameters of EP-FXT focusing mirror. Finally, the relationships among effective area, HEW, W90 and particle contamination density are calculated to characterize the influence of particle contamination on the performance of the focusing mirror. In this paper, structural and thermal model (STM) and qualification model (QM) are simulated simultaneously to make full use of their test data. By comparing the simulation results of STM effective area with the measured results, we find that the simulation results of STM effective area are accurate. When the EP-FXT is in orbit (the contamination amount is limited to less than 1.1 × 10<sup>–3</sup>), the effective area and angle resolution (HEW) meet the development requirements of EP-FXT. For the simulation of HEW, both QM and STM are in good agreement with the test results. The simulation results of HEW and effective area can be used to quantitatively analyze the effect of particle contamination on the performance of the focusing mirror. These quantitative analysis results provide a theoretical basis for the contamination prevention requirements of EP-FXT.