高线对全息平焦场光栅研制

In inertial confinement fusion physics experiments, the fusion plasma diagnostics is an important method to study the state of the plasma variation with time and space. The soft X-ray flat-field grating spectrometer is one of the important diagnostic equipments, which has been built successfully covering the 2-30nm region in experimental system. However, the flat-filed soft X-ray concave grating which is the key component in the spectrometer, has to be imported from Japan. Furthermore, the export of the holographic laminar-type grating covering the high energy region from other countries to China is limited due to the special application of soft X-ray flat-field grating spectrometer. .In this project, the design and fabrication method for the flat-field concave grating covering 0.2-1.5 keV will be established. The spectral response’s inconsistence will be solved by adjusting the grating efficiency according to the charge-coupled device’s quantum efficiency. The grating’s diffraction efficiency and the suppression on higher-order light will be simulated when the surface roughness is presented in the grating groove structure. The influence of the grating line-density and the spectrometer’s geometrical configuration parameters on the spectrum resolution will be investigated to find out an effective method which would enhance the resolution by utilizing complementation effect. Based on these studies, the ultimate goal of this project is to design and fabricate the flat-field gratings having an average groove density of 2400 lines/mm in the application of a soft X-ray flat-field spectrograph covering the 0.2-1.5 keV region. Moreover, this research will provide theoretical and technical basis for the future study on the multilayer laminar-type holographic gratings in the application of soft X-ray flat-field spectrograph in the region of 1-10 keV.

在激光惯性约束聚变物理实验中，对等离子体发射的X射线光谱的研究是获得等离子体状态参数的重要手段。X射线平焦场谱仪是该类实验中的重要设备之一，国内X射线平焦场谱仪的设计和研制已经达到了实用水平，但谱仪的核心元件— X射线平焦场光栅，完全依赖进口。而由于平焦场谱仪的特殊应用背景，目前工作于高能区的优质全息光栅的进口受到限制。.本项目针对0.2-1.5 keV能区的凹面平焦场光栅的设计和制备技术开展研究。综合考虑光栅效率及探测器响应特性，解决光谱仪在工作能区内响应不均匀的问题；研究光栅槽型、粗糙度等与衍射效率及高次谐波抑制的关系；分析光栅线密度和谱仪的结构参数对能谱分辨力的影响，利用二者之间的互补效应提高分辨；研制平焦场光栅用于惯性约束聚变物理实验研究。该研究还将为1-10 keV的X射线平焦场多层膜全息光栅的研究提供理论及技术基础。

软X射线掠入射平焦场光栅谱仪是核聚变、天体物理和材料研究等领域的重要仪器，软X射线平焦场光栅是其核心元件。本课题主要研究使用在0.8-6nm波段的全息平焦场光栅的设计和制作。为了兼容现在的光谱仪结构，选取入射角度为88.65°，入射距离237mm，成像距离235mm。基于遗传算法，优化光栅的线密度分布并设计全息曝光光路的参数。同时研究光谱仪光谱分辨率的提升方法，提出分区光栅和基于柱面镜曝光的设计方法，可以有效的提升响应波段的光谱分辨率，而且两种设计方法并不冲突，两者结合可以提升整个使用波段的光谱分辨率。在光栅的制作工艺方面，系统分析了曝光光路的调节误差对线密度分布的影响，找出最敏感的影响因素，利用非球面波记录光路制作了光刻胶掩模，利用灰化技术获得期望的占宽比，最后利用离子束刻蚀将光刻胶图形转移到融石英基底上，获得了占宽比为0.35±0.1，槽深为9±1nm的Laminar全息平焦场光栅。在国家同步辐射实验室计量站上标定了4.5-8 nm波段的衍射效率，其测量结果达到理论值设计值的65%以上，同时也测量了日本岛津公司的商业全息平焦场光栅的衍射效率，结果表明制作光栅的衍射效率已达到商业光栅的水平。