强度关联三维衍射层析的实验研究

提出了一种基于强度关联成像的新型三维衍射层析技术.利用强度关联成像技术(鬼成像)可实现无透镜傅里叶变换的特点,并结合衍射层析技术和二步相位恢复算法,使用波长为650 nm的赝热光实现了强度关联三维衍射层析.详细描述了强度关联三维衍射层析的基本原理以及具体实验结果,为在第三代同步辐射光源实现非相干X光衍射成像积累了经验.     

第三代同步辐射光源X射线相干性测量研究

随着高性能第三代同步辐射光源的建成开放,基于X射线相干特性的实验方法得到了快速发展和广泛应用.作为一个典型的例子,X射线相位衬度成像已经成为常规的X射线实验方法并向用户开放.相干散射、相干衍射成像、光子关联谱等X射线实验方法正日益受到重视,在高空间分辨、时间分辨等研究领域已显示出其独特的优越性.因此,研究和测量第三代同步辐射的空间相干特性对进一步发展这些新的实验方法具有重要意义.基于Talbot自成像原理成功测量了上海光源X射线成像线站发射的X射线的空间相干长度,并进而测得了相应光源的空间尺度.光子能量为33.2 keV时,测得的X射线光束垂直方向空间相干长度为8.84μm,对应的光源尺寸为23μm,测量结果与理论分析相符.     

Development and trends in synchrotron studies of ancient and historical materials

Synchrotron photon-based methods are increasingly being used for the physico-chemical study of ancient and historical materials (archaeology, palaeontology, conservation sciences, palaeo-environments). In particular, parameters such as the high photon flux, the small source size and the low divergence attained at the synchrotron make it a very efficient source for a range of advanced spectroscopy and imaging techniques, adapted to the heterogeneity and great complexity of the materials under study. The continuous tunability of the source — its very extended energy distribution over wide energy domains (meV to keV) with a high intensity — is an essential parameter for techniques based on a very fine tuning of the probing energy to reach high chemical sensitivity such as XANES, EXAFS, STXM, UV/VIS spectrometry, etc. The small source size attained (a few micrometres) at least in the vertical plane leads to spatial coherence of the photon beams, giving rise in turn to a series of imaging methods already crucial to the field. This review of the existing literature shows that microfocused hard X-ray spectroscopy (absorption, fluorescence, diffraction), full-field X-ray tomography and infrared spectroscopy are the leading synchrotron techniques in the field, and presents illustrative examples of the study of ancient and historical materials for the various methods. Fast developing analytical modalities in scanning spectroscopy (STXM, macro-XRF scanning) and novel analytical strategies regarding optics, detectors and other instrumental developments are expected to provide major contributions in the years to come. Other energy domains are increasingly being used or considered such as far-infrared and ultraviolet/visible for spectroscopy and imaging. We discuss the main instrumental developments and perspectives, and their impact for the science being made on ancient materials using synchrotron techniques.     

同步辐射X射线荧光光谱国内外研究进展

同步辐射光源是带电粒子在加速器储存环中以接近光速的速度运动时,沿轨道切线方向发射出的辐射,同步辐射X射线荧光分析(SR-XRF)是以同步辐射X射线作为激发光源的X荧光光谱分析技术.同步辐射X射线荧光分析包括了用于微区及微量元素分析的同步辐射XRF、用于表面及薄膜分析的同步辐射全反射X射线荧光(SR-TXRF)以及用于三...     

High‐performance X‐ray detectors for the new powder diffraction beamline I11 at Diamond

The design and performance characterization of a new light‐weight and compact X‐ray scintillation detector is presented. The detectors are intended for use on the new I11 powder diffraction beamline at the third‐generation Diamond synchrotron facility where X‐ray beams of high photon brightness are generated by insertion devices. The performance characteristics of these detection units were measured first using a radioactive source (efficiency of detection and background count rate) and then synchrotron X‐rays (peak stability, light yield linearity and response consistency). Here, the results obtained from these tests are reported, and the suitability of the design for the Diamond powder beamline is demonstrated by presenting diffraction data obtained from a silicon powder standard using a prototype multicrystal analyser stage.     

Facility Update: The Center for Advanced Microstructures and Devices: A Status Report

The progress in the field of high resolution X-ray microscopy is caused in particular by the rapid developments of synchrotron radiation sources and X-ray optical elements, by the extension of the energy range, improved designs of X-ray microscopes and scanning X-ray microscopes, the use of CCD detectors with high detective quantum efficiency, the introduction of new imaging techniques, and the development of new fields of application.     

On the interest of synchrotron X-ray imaging for the study of solidification in metallic alloys

Recent developments of more powerful synchrotron sources have led to vast improvements in the performance of X-ray imaging. This is manifested by a continuous increase in the impact of synchrotron experiments in many research areas on materials, in particular solidification science. X-ray imaging has been established as a method of choice for in situ and real-time studies of solidification microstructure formation in metallic alloys, with spatio-temporal resolutions at the scales of relevance. In this article, we present illustrative results of the current capabilities of synchrotron X-ray imaging in this field of research, each of them using different X-ray techniques (radiography, topography and tomography). Those results demonstrate the high potential of these techniques for the investigation of dynamical phenomena in materials processing.     

Sheet-beam geometry for in vivo fluorescent x-ray computed tomography: proof-of-concept experiment in molecular imaging

We propose a fluorescent x-ray computed tomography method using an array of detectors with an incident sheet beam, aimed at providing molecular imaging with high sensitivity and good spatial resolution. In this study, we prove the feasibility of this concept and investigate its imaging properties, including spatial and contrast resolutions and quantitativeness, by imaging an acrylic phantom and a normal mouse brain using a preliminary imaging system with monochromatic synchrotron x rays.     

X-ray microanalysis near an absorption edge using synchrotron radiation: How to obtain quantitative results

X-ray absorption microanalysis by contact microscopy with synchrotron radiation potentially offers the advantages of high resolution and large fields. However, difficulties appear when quantitative results are required, due in particular to the image detectors that are used. The degree of confidence in quantitative results is examined for photographic detectors. Computer processing is performed taking into account several factors such as the recording process, emulsion response, alignment of image pairs for subtraction, presence of harmonics in the synchrotron beam. As an example we show the analysis of nickel in 20 μm thick polymetallic nodule section on an area of 5.1 × 5.1 mm².     

The Status of the Australian Synchrotron

The earliest Australian use of a synchrotron can be dated to 1976 using the accelerator at Daresbury to perform energy dispersive diffraction crystallography of complex mineral structures. This was while it was operating in a parasitic mode in the days before it became a synchrotron storage ring. During the 1970s and 1980s, Australian researchers undertook experiments to study gas-phase atomic structures using Auger spectroscopy at the LURE facility in Paris; protein crystallography at Daresbury, DESY, Photon Factory, and SPEAR; NEXAFS experiments on thin polymer films at SSRL; development of a novel toroidal analyzer for angle-resolved photoelectron spectroscopy at BESSY 1 and later on BESSY 2; and carry out X-ray diffraction and XAFS at the Photon Factory.     

The impact of infrared synchrotron radiation in biology: Past,present and future

The Synchrotron Radiation Center (SRC) at the University of Wisconsin-Madison was shut down permanently in March 2014. It began operation in 1968 as the world's first dedicated synchrotron radiation user facility. This revolutionary idea of using synchrotron radiation for broad support of science and technology proved a resounding success, and it subsequently led to worldwide development of ever more powerful light sources for R&;D in many major scientific and technical areas. With upgrades and groundbreaking initiatives, SRC remained a cutting-edge and cost-effective facility to the end. SRC filled an important niche for tough experiments that were not possible at the newer facilities, given their beam time constraints. The world of IR, VUV, and soft X-ray research has been diminished by its loss, but its closing was necessitated by higher priorities at the US NSF.     

Lifetime measurements of colour centres by a multifrequency phase fluorometer

Summary The first measurements of emission lifetimes in colour centres using a cross correlation phase and modulation fluorometer operating at the synchrotron radiation facility PULS (Frascati) are reported. Preliminary results on the F and F-aggregate centres in NaF are briefly summarized.

---

Riassunto Si riportano le prime misure di tempi di vita dell'emissione dei centri di colore usando uno spettrofluorometro a correlazione di fase e di modulazione in funzione presso il laboratorio del Programma per l'Utilizzazione della Luce di Sincrotrone (PULS, Frascati). Si discutono i risultati relativi ai centri F ed agli aggregati di centri F nel fluoruro di sodio.

     

无透镜显微成像的重构算法研究

针对单幅图像进行了无透镜显微成像的重构算法研究，介绍了无透镜显微成像系统实验装置和ASM(angle spectrum method)、改编后的L-R(Lucy-Richardson)两种重构算法。对比两种算法重构后的USAF分辨率板图像的分辨率，利用瑞利判据得出ASM获得的振幅图分辨率最高(即3.10 μm)，且计算用时最少(即0.9 s)，证明了ASM为最佳的单幅无透镜显微重构算法。其次，利用无透镜显微成像系统结合ASM重构的方法，进行细胞成像实验。该无透镜成像视场为5×显微镜的4.4倍，且分辨率介于5×及10×光学显微镜之间，统计学优势明显，在生物医学领域具有广阔的应用前景。     

上海光源硬X射线相干衍射成像实验方法初探

相干X射线衍射成像方法是一种先进的成像技术,分辨率可达纳米量级.国际上大多数的同步辐射装置和自由电子激光装置都建立了该成像方法,并有将其作为主要成像技术的趋势.上海光源作为目前国内唯一的一台第三代同步辐射光源,尚未建立基于硬X射线的相干衍射成像实验平台.随着一批以波荡器为光源的光束线站投入使用,使得该方法的建立成为了可能.本文基于上海光源BL19U2生物小角散射线站,通过有效的光路设计,搭建了相干衍射实验平台,在12 keV和13.5 keV能量点均获得了硬X射线相干光束,并基于小孔衍射测量了入射光束的空间相干长度.该平台支持常规和扫描相干衍射实验模式,对小孔衍射图样及波带片扫描衍射图样实现了正确的相位重建,证明了该平台初步具备开展硬X射线相干衍射成像实验的能力.硬X射线相干衍射成像实验平台为国内首次建立,将为国内该实验方法的发展和应用提供有效的软硬件支持.     

Design and construction of multicrystal analyser detectors using Rowland circles: application to MAD26 at ALBA

A concept is given for describing multicrystal analyser detectors (MADs), as they are in use for synchrotron powder diffraction, on the basis of the Rowland circle construction. The Rowland circle is typically used to describe focusing geometries and can be adapted for the case of MADs working at a single energy as well as in a limited energy range. With this construction it is also possible to quantify and optimize the walk of the beam along non‐central crystals which is inevitable in certain detector designs. The results of this geometrical inspection are correlated with a real detector design that is implemented at the ALBA synchrotron facility in Spain. An error budget is given to estimate the influence and amount of tolerance of the manufacturing process.     

Advances in synchrotron hard X-ray based imaging

Modern synchrotron radiation (SR) sources have dramatically fostered the use of SR-based X-ray imaging. The relevant information such as density, chemical composition, chemical states, structure, and crystallographic perfection is mapped in two, or, increasingly, in three dimensions. The development of nano-science requires pushing spatial resolution down towards the nanoscale.The present article describes a selection of hard X-ray imaging and microanalysis techniques that emerged over the last few years, by taking advantage of the flux and coherence of the SR beams, as well as exploiting the advances in X-ray optics and detectors, and the increased possibilities of computers (memory, speed). Examples are given to illustrate the opportunities associated with the use of these techniques, and a number of recent references are provided. To cite this article: J. Baruchel et al., C. R. Physique 9 (2008).     

光源尺寸和光谱带宽对波带板成像的影响

X射线菲涅耳波带板成像能实现亚微米空间分辨能力,有可能应用于激光等离子体或聚变靶的高分辨X射线成像诊断.之前的数值模拟研究表明,成像分辨能力受光源尺寸、入射光或成像光谱带宽的影响.本文报道在632.8 nm为中心波长的可见光波段,对波带板成像的数值模拟和原理性验证实验.数值模拟表明:随着扩展光源尺寸增加,视场中央分辨能力基本不变,而像对比度下降;随着成像的光谱带宽的增加,视场中央分辨能力与像对比度同时下降.实验证实了数值模拟的结论,且实验与数值模拟结果的定量比较也符合得较好.     

An ART iterative reconstruction algorithm for computed tomography of diffraction enhanced imaging

X-ray diffraction enhanced imaging (DEI) has extremely high sensitivity for weakly absorbing low-Z samples in medical and biological fields. In this paper, we propose an Algebra Reconstruction Technique (ART) iterative reconstruction algorithm for computed tomography of diffraction enhanced imaging (DEI-CT). An Ordered Subsets (OS) technique is used to accelerate the ART reconstruction. Few-view reconstruction is also studied, and a partial differential equation (PDE) type filter which has the ability of edge-preserving and denoising is used to improve the image quality and eliminate the artifacts. The proposed algorithm is validated with both the numerical simulations and the experiment at the Beijing synchrotron radiation facility (BSRF).     

Mapping of the metal intake in plants by large-field X-ray microradiography and preliminary feasibility studies in microtomography

This paper reports on dual energy micro-radiography and tomography techniques applied both to thin plant leaves treated with copper or lead solutions and on Cu-treated small roots and stem sections, performed at the SYRMEP X-ray beamline of ELETTRA synchrotron facility in Trieste (Italy). The features of the source allowed us to apply different imaging techniques with an extremely vast field of view, up to 160 ×6 mm2 and 28×6 mm2 for micro-radiography and tomography experiments, respectively. The feasibility of getting positive indications on metal accumulation in leaves, sections of roots and stems, stem and root whole cylindrical pieces has been checked.