X射线变线距矩形多层膜光栅的理论模型与制备方法研究

Most modern synchrotron beamline spectrometers and monochromators utilize variable line spacing gratings rather than constant groove density gratings due to the fact that flat-field focusing and aberration control can all be combined in one element. Traditional single layer gratings cannot offer enough flux for spectroscopy techniques such as resonant inelastic X-ray scattering requiring high flux and high spectral resolution. One of the most promising candidates is to cover gratings with multilayers, which can increase the acceptance in soft X-ray region compared to traditional gratings, obtain higher flux than crystals in hard X-ray region, and reflect efficiently in tender X-ray region. The goal of this project is to study the theoretical model and fabrication methods of X-ray variable line spacing alternate multilayer gratings. We will establish the X-ray diffraction model for variable line spacing alternate multilayer gratings, and design grating structures based on target experiment requirements; set up the fabrication workflow for multilayer gratings with variable line spacing, and optimize the multilayer deposition parameters for grating substrate; explore new material combination and multilayer grating structures, aiming to provide technology support for the development of X-ray spectroscopy.

现代同步辐射光谱仪及单色器在软X射线波段大多采用变线距光栅，实现色散、像差控制及平场聚焦。传统单层膜光栅无法满足共振非弹性X射线散射技术等高通量高光谱分辨率谱学实验的需求。多层膜光栅可以在软X射线波段获得比传统光栅高的集光效率、在硬X射线波段获得比晶体大的光通量，填补韧X射线波段高效率色散元件的空白。目前，相关研究大多集中在等线距多层膜光栅。本项目计划研究X射线变线距矩形多层膜光栅的理论模型与制备方法。研究内容包括：建立变线距矩形多层膜光栅的X射线衍射模型，并针对具体实验需求设计目标结构；建立变线距多层膜光栅的工艺流程，优化变线距光栅基底上多层膜的沉积工艺；探索新材料组合与结构特征的变线距多层膜光栅设计，为X射线谱学实验的发展提供技术支持。

现代同步辐射光谱仪及单色器大多在软X射线波段采用变线距光栅，实现色散、像差控制及平场聚焦。传统单层膜光栅无法满足共振非弹性X射线散射技术等高通量高分辨率谱学实验的需求。依托多层膜高反射率特性的多层膜光栅可以在提升能量分辨率的同时保持较高的衍射效率。目前相关研究大多集中在等线距的多层膜光栅，本项目研究了X射线变线距多层膜光栅的设计模拟与制备方法。研究内容包括：1)平场变线距多层膜光栅光谱仪的理论研究与设计，将多层膜变线距光栅应用于高通量极紫外光谱仪，针对谱学实验需求进行了多层膜变线距光栅结构的设计与模拟，优化后光谱仪的通量相比传统光栅光谱仪高一个量级；2)多层膜结构在辐射条件下的材料和光学性能研究，对Cr/C多层膜的耐辐射损伤现象和原理进行了研究；3)耐辐照损伤光栅基底的制备工艺研究，对金刚石光栅基底的制备方法、工艺参数进行了探索；4)高线密度多层膜光栅的制备与测试，基于2万线密度自主装生长的GaAs光栅基底，设计并制备了多层膜光栅，通过对光栅轮廓和衍射效率的测试说明其性能与理论基本吻合。本项目的研究探索了多层膜变线距光栅的理论设计与制备方法，为高通量、高能量分辨率X射线光栅光谱仪/单色器的设计提供了新方法。