软X射线显微成像位相型波带片浅析

软X射线显微成像技术是研究超微观世界的有力工具,而位相型波带片则以其高分辨率的优势,目前已成为实现软X射线成像的理想光学元件.本文简要介绍位相型波带片的特性及其在软X射线显微成像技术中的应用.     

高分辨率软X射线显微成像原理及其应用

软X射线显微成像具有分辨率高、辐射损伤小以及能够对含水的生物样品直接进行显微成像等独特的优势,目前已成为研究生命科学和生物学等学科中的超微观世界的特殊工具.本文简要介绍基于波带片的高分辨率软X射线显微成像的原理及其应用.     

高分辨率X射线显微成像及其进展

介绍了高分辨率X射线显微成像产生背景和发展过程，着重分析了基于光学元件波带片的放大成像的基本原理，并简述了高分辨率三维成像的有关理论。同时给出国内外高分辨率X射线显微成像研究的最新进展，展望了高分辨率X射线显微成像的应用前景。     

18.2nm Schwarzschild显微成像系统初步研究

叙述了Schwarzschild型正入射软X射线多层膜显微成像系统的设计、制作和成像实验，其工作波长为18．2nm，放大倍数为10．5×，极限分辨率小于0．2μm。采用Mo／Si多层膜，周期和层数分别为9．5nm和41。用激光等离子体光源对20pl／mm和55pl／mm的栅网进行了软X射线显微成像实验，所得结果表明此显微成像系统的分辨率在微米量级。     

同步辐射X射线相衬显微CT在古生物学中的应用

X射线无损成像技术在古生物化石标本研究领域中应用十分广泛.近几年来,随着技术的不断革新,同步辐射X射线相衬显微断层成像技术(SRX-PC-μCT)也被引入到这一领域.由于同步辐射光源产生的硬X射线具有高亮度、高准直性和高空间相干性等优点,可以实现化石标本高分辨率(亚微米级)的无损三维显微成像,给古生物学的发展带来了新的机遇.文章简要回顾了用于古生物化石标本无损成像技术的发展历程,并在此基础L综述了同步辐射X射线断层显微成像技术在古生物学领域的应用现状和前景.     

同步辐射讲座 第三讲 软X射线显微术

对生物样品的研究，软X射线显微术具有独特的优势，例如，它能够对较厚的活性含水的生物样品直接进行显微成像以及元素分布的微区分析等，文章简要论述了软X射线显微术的衬度机制及其优势；列表概括了包括SCXM，TXM，STXM，Gabor全息以及衍射等几种类型的X射线显微术的基本特性；简要综述了合肥国家同步辐射实验室（NSRL）软X射线显微术的研究进展。     

正入射软X-射线显微成像系统聚光镜设计

 依据正入射软X 射线显微成像系统对聚光镜的要求, 论述了采用掠入射聚光镜是最佳选择。在分析聚光镜几何参数的基础上, 决定了确定椭球面聚光镜的方法。在考虑材料反射特性和实际制作椭球面镜方法的同时, 确定了要研制的高分辨率显微成像系统用聚光镜的结构参数。     

同步辐射X射线三维显微成像

本介绍了利用同步辐射进行X射线三维成像的工作原理及进展状况,详细论述了X射线三维成像的两种方法,X射线全息及CT技术,以及通过两的结合（HCT）进行高分辨率三维成像的有关理论与实验技术;介绍了同轴全息中消除“双生像”噪声的数字方法,讨论了影响分辨率的各种因素;本还介绍了在国家同步辐射实验室软X射线实验站进行的生物样品X射线三维成像的实验及其结果。     

同步辐射软X射线接触显微成像

软Ｘ射线显微术适合于自然状态下生物样品的高分辨率显微成像。软Ｘ射线接触显微术是Ｘ射线显微成像方法中最简单也是迄今唯一到接近理论分辨的方法。本文阐述软Ｘ射线接触显微成像的原理和方法，并报告用合理肥步辐射光源进行软Ｘ射线接触显微成像的一些实验结果。     

同步辐射相位衬度成像医学应用初探

近年来,相位衬度成像技术医学领域应用的发展引人瞩目.同步辐射相位衬度成像无须使用对比剂就能显示传统X射线无法显示的肌腱、软骨、韧带、脂肪、血管及神经等软组织.文章作者应用包括类同轴相衬成像和衍射增强成像在内的相位衬度成像技术进行了肝胆、肺脏、肾脏、胃肠道、心脏、血管、骨关节组织与肿瘤成像,证实了同步辐射相位衬度成像较传统X射线成像图像清晰,分辩率明显提高,特别适用于软组织、血管等的成像.     

Multivariate analysis of hyperspectral hard X‐ray images

This article describes methods to analyse and process hyperspectral hard X‐ray imaging data. We focus on the use of multivariate techniques that exploit the spectral information to make informed decisions on the material content within each pixel of an X‐ray image. These analysis methods have the ability to auto‐segment data without prior knowledge of the sample composition or structure, and are particularly useful for studying completely unknown, diluted or complex specimens. We demonstrate the methods on a variety of hard X‐ray images including X‐ray fluorescence and absorption data recorded using a hard X‐ray imaging spectrometer. The multivariate methods described are very powerful with the ability to segment, distinguish and, in some cases, identify different materials within a single X‐ray image. Potential uses of hyperspectral X‐ray imaging are discussed varying from materials science to industrial or security applications. Copyright © 2013 John Wiley & Sons, Ltd.     

同步辐射的相干模式

在分析了光源相干相体积的基础上，重点研讨了第三代同步辐射中波荡器（ｕｎｄｕｌａｔｏｒ）辐射的相干模式，能谱亮度，相干光子通量等，这对提高光束线相干能量的传输效率和软Ｘ光相干学束线的设计具有重要意义。     

Current status of the TwinMic beamline at Elettra: a soft X‐ray transmission and emission microscopy station

The current status of the TwinMic beamline at Elettra synchrotron light source, that hosts the European twin X‐ray microscopy station, is reported. The X‐ray source, provided by a short hybrid undulator with source size and divergence intermediate between bending magnets and conventional undulators, is energy‐tailored using a collimated plane‐grating monochromator. The TwinMic spectromicroscopy experimental station combines scanning and full‐field imaging in a single instrument, with contrast modes such as absorption, differential phase, interference and darkfield. The implementation of coherent diffractive imaging modalities and ptychography is ongoing. Typically, scanning transmission X‐ray microscopy images are simultaneously collected in transmission and differential phase contrast and can be complemented by chemical and elemental analysis using across‐absorption‐edge imaging, X‐ray absorption near‐edge structure or low‐energy X‐ray fluorescence. The lateral resolutions depend on the particular imaging and contrast mode chosen. The TwinMic range of applications covers diverse research fields such as biology, biochemistry, medicine, pharmacology, environment, geochemistry, food, agriculture and materials science. They will be illustrated in the paper with representative results.     

X‐ray spectra by means of Monte Carlo simulations for imaging applications

X‐ray tubes have a broad range of applications worldwide, including several techniques for atomic physics, like X‐ray fluorescence, as well as for medical imaging, like computed tomography. The performances of X‐ray imaging detectors have shown to be significantly sensitive to the incident beam spectrum. Therefore, an accurate knowledge of the X‐ray beam becomes necessary for the emission source characterization and the whole imaging process comprehension. Direct measurements and suitable Monte Carlo simulations may be used to establish the X‐ray spectra. Dedicated Monte Carlo simulation routines, based on the PENELOPE code, have been developed to determine the Bremsstrahlung X‐ray spectra generated by conventional X‐ray tubes. The simulated spectra have been validated by comparison with the corresponding experimental data showing an overall good agreement. The incorporation of a suitably designed virtual grid allowed to assess the angular distribution of Bremsstrahlung yield, showing a remarkable anisotropy. In addition, a dedicated program has been developed for virtual imaging, which enables to perform suitable X‐ray absorption contrast images. Also, the developed program includes a user‐friendly graphic interface to allow the upload of required input parameters, which include setup arrangement, beam characteristics, sample properties and image simulation parameters (spatial resolution, tracks per run, etc.). The software includes dedicated subroutines which handle the physical process from X‐ray generation up to detector signal acquisition. The aim of the developed program is to perform virtual imaging by means of absorption contrast and using conventional X‐ray sources, which may be a useful tool for the study the X‐ray imaging techniques in several research fields as well as for educational purposes. The performed comparisons with experimental data have shown good agreement. The obtained results for X‐ray imaging may constitute useful information for the comprehension and improvement of X‐ray image quality, like absorption contrast optimization, detail visualization, definition and detectability. Copyright © 2010 John Wiley & Sons, Ltd.     

X‐ray focusing by the system of refractive lens(es) placed inside asymmetric channel‐cut crystals

An X‐ray one‐dimensionally focusing system, a refracting–diffracting lens (RDL), composed of Bragg double‐asymmetric‐reflecting two‐crystal plane parallel plates and a double‐concave cylindrical parabolic lens placed in the gap between the plates is described. It is shown that the focal length of the RDL is equal to the focal distance of the separate lens multiplied by the square of the asymmetry factor. One can obtain RDLs with different focal lengths for certain applications. Using the point‐source function of dynamic diffraction, as well as the Green function in a vacuum with parabolic approximation, an expression for the double‐diffracted beam amplitude for an arbitrary incident wave is presented. Focusing of the plane incident wave and imaging of a point source are studied. The cases of non‐absorptive and absorptive lenses are discussed. The intensity distribution in the focusing plane and on the focusing line, and its dependence on wavelength, deviation from the Bragg angle and magnification is studied. Geometrical optical considerations are also given. RDLs can be applied to focus radiation from both laboratory and synchrotron X‐ray sources, for X‐ray imaging of objects, and for obtaining high‐intensity beams. RDLs can also be applied in X‐ray astronomy.     

X荧光分析系列实验

介绍了能量色散X射线荧光分析的原理、应用以及用X荧光谱仪开设的系列实验。     

便携式脉冲X射线成像系统研究

便携式脉冲X射线成像系统主要由脉冲X射线源、数字化记录系统和笔记本电脑组成。主要介绍了系统的硬件(脉冲源和图像采集控制卡)和应用软件的设计过程。这种便携式脉冲X射线成像系统具有剂量小、重量轻和成像质量高,目前已应用到公安系统的安全检查等部门。     

Versatility of a hard X‐ray Kirkpatrick–Baez focus characterized by ptychography

In the past decade Kirkpatrick–Baez (KB) mirrors have been established as powerful focusing systems in hard X‐ray microscopy applications. Here a ptychographic characterization of the KB focus in the dedicated nano‐imaging setup GINIX (Göttingen Instrument for Nano‐Imaging with X‐rays) at the P10 coherence beamline of the PETRA III synchrotron at HASLYLAB/DESY, Germany, is reported. More specifically, it is shown how aberrations in the KB beam, caused by imperfections in the height profile of the focusing mirrors, can be eliminated using a pinhole as a spatial filter near the focal plane. A combination of different pinhole sizes and illumination conditions of the KB setup makes the prepared optical setup well suited not only for high‐resolution ptychographic coherent X‐ray diffractive imaging but also for moderate‐resolution/large‐field‐of‐view propagation imaging in the divergent KB beam.     

X‐ray grating interferometer for biomedical imaging applications at Shanghai Synchrotron Radiation Facility

An X‐ray grating interferometer was installed at the BL13W beamline of Shanghai Synchrotron Radiation Facility (SSRF) for biomedical imaging applications. Compared with imaging results from conventional absorption‐based micro‐computed tomography, this set‐up has shown much better soft tissue imaging capability. In particular, using the set‐up, the carotid artery and the carotid vein in a formalin‐fixed mouse can be visualized in situ without contrast agents, paving the way for future applications in cancer angiography studies. The overall results have demonstrated the broad prospects of the existing set‐up for biomedical imaging applications at SSRF.     

Phase-contrast X-ray imaging of the gas diffusion layer of fuel cells

The understanding of and in situ observation of the transport and distribution of water in carbon‐paper gas diffusion layers (GDLs) using non‐destructive imaging techniques is critical for achieving high performance in polymer electrolyte fuel cells (PEFCs). To investigate the behavior of water in GDLs of PEFCs, phase‐contrast X‐ray imaging via X‐ray interferometric imaging (XII) and diffraction‐enhanced imaging (DEI) were performed using 35 keV X‐rays. The XII technique is useful for the radiographic imaging of GDLs and in situ observations of water evolution processes in operating PEFCs. DEI provides a way for tomographic imaging of GDLs in PEFCs. Because high‐energy X‐rays are applicable to the imaging of both carbon papers and heavy materials, which make up PEFCs, phase‐contrast X‐ray imaging techniques have proven to be valuable for investigation of GDLs.