在掠入射X射线望远镜中X射线散射对成像退化贡献的分析评估
Analytical evaluation of the X-ray scattering contribution to imaging degradation in grazing-incidence X-ray telescopes
摘要：
X射线光学器件的聚焦性能（方便地用HEW，半能宽表示）强烈地依赖于反射镜变形和由反射表面的微观粗糙度引起的光子散射。特别地，X射线散射（XRS）对光学器件的HEW的贡献通常是光子能量E的增函数H（E）。因此，在未来的硬X射线成像望远镜（SIMBOL-X、NeXT、Constellation-X、XEUS）中，X射线散射可能是主要问题，因为它们也将在硬X射线波段（即超过10 keV）中操作。[...]在过去的几年中，提出了几种方法来估计散射的HEW的贡献，处理的表面微观粗糙度表示的功率谱密度（PSD），从粗糙表面的X射线散射的成熟理论的基础上。我们在相同的理论基础上面临这个问题，但我们尝试了一种新的方法：将给定的表面粗糙度PSD直接解析转换为H（E）趋势，反之亦然-将H（E）要求直接转换为表面PSD。该PSD表示为了满足给定X射线望远镜的能量带中的H（E）要求而容许的最大微观粗糙度水平。因此，我们已经找到了一种新的，分析和广泛适用的形式主义来计算XRS的HEW的贡献，从表面PSD，提供的PSD已被测量在一个广泛的空间频率范围。反问题也得到了解决，允许从测量的函数H（E）的反射镜表面PSD的即时评估。相同的形式允许建立反射镜的最大允许PSD，以满足给定的H（E）要求。[...]
英文摘要：
The focusing performance of X-ray optics (conveniently expressed in terms of HEW, Half Energy Width) strongly depend on both mirrors deformations and photon scattering caused by the microroughness of reflecting surfaces. In particular, the contribution of X-ray Scattering (XRS) to the HEW of the optic is usually an increasing function H(E) of the photon energy E. Therefore, in future hard X-ray imaging telescopes of the future (SIMBOL-X, NeXT, Constellation-X, XEUS), the X-ray scattering could be the dominant problem since they will operate also in the hard X-ray band (i.e. beyond 10 keV). [...] Several methods were proposed in the past years to estimate the scattering contribution to the HEW, dealing with the surface microroughness expressed in terms of its Power Spectral Density (PSD), on the basis of the well-established theory of X-ray scattering from rough surfaces. We faced that problem on the basis on the same theory, but we tried a new approach: the direct, analytical translation of a given surface roughness PSD into a H(E) trend, and - vice versa - the direct translation of a H(E) requirement into a surface PSD. This PSD represents the maximum tolerable microroughness level in order to meet the H(E) requirement in the energy band of a given X-ray telescope. We have thereby found a new, analytical and widely applicable formalism to compute the XRS contribution to the HEW from the surface PSD, provided that the PSD had been measured in a wide range of spatial frequencies. The inverse problem was also solved, allowing the immediate evaluation of the mirror surface PSD from a measured function H(E). The same formalism allows establishing the maximum allowed PSD of the mirror in order to fulfill a given H(E) requirement. [...]
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