EP-FXT聚焦镜真实表面状态的性能模拟方法

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

后随X射线望远镜(follow-up X-ray telescope,FXT)是爱因斯坦探针卫星的主要载荷之一.为了获取高信噪比的数据,实现对观测天体的高精度定位,FXT使用Wolter-Ⅰ型X射线聚焦光学系统,该系统一直是X射线空间天文观测中的重要设备.根据Wolter-Ⅰ型的聚焦原理,结合实际的加工特点,利用蒙特卡罗模拟算法对影响光学成像质量的几个关键参量,如表面粗糙度、面形误差进行了模拟,结合模拟结果对各参量的作用效果进行了分析.之后利用PANTER实验室提供的聚焦镜性能测试结果对模拟方法进行了验证,同时对面形误差参量进行了限制.最终聚焦镜结构热控件半能量宽度(half energy width,HEW)模拟与实测结果基本一致.该模拟过程可以很有效地应用于聚焦镜加工工艺的摸索,为FXT的聚焦镜测试和标定工作提供参考.结合实测标定数据,该模拟方法生成的有效面积、渐晕和点扩散函数等可用于在轨观测标定数据库.

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