Khubbutdinov R, Geloni G, Saldin E, Bagschik K
Opt Express. 2024 Dec 30;32(27):47810-47828. doi: 10.1364/OE.542077.
Fourth-generation synchrotron sources promise an enormous increase in the spatial coherence of X-ray radiation. In the EUV to soft X-ray range, the spatial coherence could reach almost 100% in both the horizontal and vertical directions. Identifying and understanding potential sources of degradation in the spatial coherence of X-rays transported along the beamline is critical to enable optimal performance for the experiments at the beamlines. Grating monochromators are an essential optical component of most EUV and soft X-ray beamlines. Recently, we have found that the spatial coherence is strongly degraded by the gratings used in these monochromators. In this work, we present a detailed physical and theoretical description of the origin and underlying effects that cause this degradation and describe the influence of the grating parameters and the exit slit of the monochromator. The theoretical analysis is presented in the framework of statistical optics. It is important to note that the described effects in the paper are distinct from the decoherence effects based on optics vibrations and the resulting virtual source broadening or wavefront degradation caused by surface irregularities and optical roughness.
第四代同步辐射光源有望极大提高X射线辐射的空间相干性。在极紫外到软X射线波段，水平和垂直方向的空间相干性几乎都能达到100%。识别并理解沿光束线传输的X射线空间相干性潜在的退化源，对于实现光束线实验的最佳性能至关重要。光栅单色仪是大多数极紫外和软X射线光束线的重要光学组件。最近，我们发现这些单色仪中使用的光栅会严重降低空间相干性。在这项工作中，我们详细阐述了导致这种退化的起源和潜在效应的物理及理论描述，并描述了光栅参数和单色仪出射狭缝的影响。理论分析是在统计光学框架内进行的。需要注意的是，本文所述效应与基于光学振动以及由表面不规则性和光学粗糙度导致的虚拟源展宽或波前退化的退相干效应不同。
