针对国内硬X射线天文观测的需求,研究了1~30 keV能段圆锥嵌套Wolter-I型X射线天文望远镜的光学设计,推导了嵌套层之间的结构递推关系,给出了合理的望远镜初始结构。在最内层和最外层之间,设计了6组W/B4C宽带非周期多层膜,模拟得到系统的有效集光面积和分辨力。理论有效集光面积达到127 cm2(在2 keV处)和71 cm2(在30 keV处),系统角分辨力约10″。系统实际成像质量还受到公差的影响,引起像质下降的公差主要有辐条位置公差、镜面位置公差和镜面面形公差。目前演示实验方便改善的公差是辐条位置公差,给出了此公差的计算方法并对系统进行光线追迹,得到了成像点列图和分辨力改变情况。辐条位置公差从±15 μm缩小到±3 μm后,系统分辨力由1′提高到13″。

Optical design of nested conical Wolter-I X-ray telescope covering energy band from 1 to 30 keV was investigated. Recurrence relation of the nested structure was deduced. Depending on the needs for hard X-ray astronomical observations in China, the initial structure was presented, for which six groups of W/B4C aperiodic multilayers were designed between the innermost and the outermost shell of mirror. The simulation results showed that the effective area could achieve 127 cm2 (at 2 keV) and 71 cm2 (at 30 keV), and the resolution was estimated to be ~10″ in half-power diameter. The actual image quality is also affected by tolerance. The main tolerances lowering image quality are position error, figure error and off-roundness. Tolerance to be improved most easily in the lab is off-roundness caused by bar. The spot diagram distribution and resolution was given after calculating off-roundness and ray tracing.When the bar position tolerance was changed from ±15 μm to ±3 μm, the responding resolution was improved from 1′ to 13′.