研究X射线散射法在软X射线掠入射望远镜反射镜的表面粗糙度测量中的应用。首先, 在光滑表面近似和细光束条件下, 根据Harvey-Shack表面散射理论得出反射镜的面形仅影响总反射光分布中的镜向部分, 对散射部分的影响可以忽略不计; 然后设计了X射线散射法测量Wolter-I型软X射线掠入射望远镜的表面粗糙度的实验方案, 并且对引起系统误差的主要因素进行了分析, 确定了进行仿真实验时的参数; 最后用Zemax对实验方案进行了仿真。在空间频率高于28/mm时, 表面粗糙度的仿真测量结果与真值吻合得非常好。本文研究结果显示: 在光滑表面近似和细光束条件下, 反射镜的面形仅影响表面粗糙度的低频部分的测量准确性, 对高频部分测量准确性的影响可以忽略不计, 利用X射线散射法可以准确测量软X射线掠入射望远镜的表面粗糙度。

The X-ray scattering method is investigated in application of characterizing surface roughness of X-ray grazing incidence telescope. The surface figure effect on the scattering diagram of the curved rough mirror is analyzed in detail based on generalized Harvey-Shack surface scatter theory and image formation theory, when smooth-surface approximation is met and the width of the incident beam is about one tenth of spatial wavelength of the surface figure. Based on the analysis, the characterizing scheme is designed and the determination error of the one-dimensional power spectral density function due to the finite width of the receiving slit before the detector is discussed. The scheme is simulated with Zemax and the simulated results verify that the surface figure only affects the measuring accuracy of the low-spatial-frequency surface roughness. The method overcomes difficulty in measuring roughness of the grazing incidence mirror with high resolution conveniently during the development of the X-ray grazing incidence telescope.