基于同步辐射光源的扫描菲涅耳相干衍射成像方法学研究

The coherent diffractive imaging (CDI) method is a new and powerful microscopy technique for imaging materials and biological specimens in both two and three dimensions. The scanning coherent diffractive imaging (or named ptychography) technique using third-generation synchrotron radiation sources has advantages of strong penetration ability, ultra-high resolution and large-area fast imaging and so on, which is an important development direction in x-ray microscopy field at current and in future. In view of its widely application and hysteretic research in China, this project aims to develop ptychographic coherent diffractive imaging method and its application based on soft x-ray scanning transmission microscopy (STXM) beamline in Shanghai Synchrotron Radiation Facility. Study how to construct the experimental setup, choose reasonable conditions to quickly carry out experiment. Optimize phase retrieval algorithm to reconstruct nano-resolution sample images more rapidly. Investigate adding beamstop in front of CCD detector to prolong exposure time in oder to improve the acquisition of high-frequency signal, which improve the resolution of retrieval sample images. Perform further study on three-dimensional imaging of ptychographical coherent diffractive imaging. Combination STXM and ptychography method to study application of two-dimensional, three-dimensional imaging of real samples, including elemental distribution imaging and spectroscopy analysis.

相干衍射成像技术是一种新型的、有效的对材料和生物样品进行二维、三维纳米级分辨成像的显微技术。采用第三代同步辐射光源的扫描相干衍射成像技术具有强穿透性、超高分辨率和大面积快速成像等优势，是当前及未来X射线成像领域一个重要的发展方向。鉴于该成像技术的重要应用及国内在该领域研究相对滞后，本项目旨在上海光源软X谱学显微线站（STXM）开展X射线扫描菲涅耳相干衍射成像方法学研究及应用。研究实验平台搭建，合理选择实验条件快速开展实验。优化编写的位相重建算法，快速重建出纳米分辨率的样品图像。研究在CCD前加装挡光板延长曝光时间，提高对高频信号的采集能力，从而提高成像分辨率。研究扫描相干衍射成像的三维成像技术。配合使用STXM成像模式和扫描相干衍射成像技术对实际样品进行二维、三维成像应用研究，包括元素分布成像及谱学分析。

针对在上海光源软X射线谱学显微线站开展扫描相干衍射成像方法学研究及应用，申请人经过三年的科学研究，在多个方面取得了良好的研究结果。当前已完成实验平台的搭建并进行了优化，实现数据采集时间缩短为传统STXM成像时间的三分之一，曝光计量缩短为原来的十分之一以上，分辨率提高到原来的三倍以上，实现最高空间分辨率优于10nm。通过优化位相重建算法和考虑各种影响因素，在GPU工作站上实现快速重建，通常可以在数分钟内重建出高质量的样品图像。在平台上实现了加装挡光板，实现对高频信号的采集时间提高五十倍以上，这在散射实验中得到了良好的实际应用。实现了等斜率模式的三维成像技术，重建出高质量的三维图像。采用不同样品进行了大量的应用研究，实现了二维元素成像和谱学分析，并对用户进行开放。