上海光源首期Wiggler真空室材料选择及测试

本文对上海同步辐射光源(Shanghai Synchrotron Radiation Facility,SSRF)首期两台扭摆器(Wiggler)真空室研制中材料的选择进行了阐述,在国内首次采用不锈钢真空室内壁镀铜的工艺来减小束流尾场效应,并对SS304镀铜材料相关真空性能进行了测试,为将来加速器设备真空室设计提供了参考.     

同步辐射原位X射线散射技术在纳米与能源材料中的应用

同步辐射原位X射线散射技术可以实现对材料结构进行多尺度的、无损的、高时间空间分辨率的表征,动态地揭示材料微观结构在不同外界环境下的演变过程。X射线散射基础理论已经相对成熟。第三代同步辐射光源大幅提高了X射线散射技术的时空分辨率,进一步拓宽X射线散射技术的应用场景。当前同步辐射原位X射线散射技术的难点主要集中于实验装置设计和大数据处理。概述了X射线散射技术的主要分类和基本的实验方法,主要介绍了不同分类的同步辐射原位X射线散射技术在纳米材料(纳米颗粒生长和纳米颗粒自组装)与能源材料(以钙钛矿薄膜材料为代表)研究中的应用。最后结合当前国内外先进同步辐射光源的发展现状,展望了同步辐射原位X射线散射技术未来发展的方向和应用前景。     

同步辐射高能X射线衍射在材料研究中的应用进展

同步辐射是具有连续光谱宽波段、高通量、低发散度等优点的先进脉冲X射线光源,可用于开展其它光源无法实现的诸多前沿科学研究。第三代同步辐射光源产生的高能X射线,能大幅提高衍射的倒易空间分辨率、穿透深度及时间分辨能力,实现使役条件下工程材料与部件内部多尺度微结构单元的高效原位、精确无损表征。配备满足透射几何条件、能施加多种力物性环境的原位装置,有助于建立多场耦合下材料的跨尺度力学模型。简述了同步辐射高能X射线衍射的基本原理、第三代同步辐射光源的装置与特点,介绍了高能X射线衍射在材料形变行为、相变以及再结晶等领域的研究进展。最后基于国内外先进光源的发展现状,展望了同步辐射高能X射线衍射技术进步的主要方向。     

X射线吸收精细结构在材料科学中的应用

X射线吸收精细结构(XAFS)方法是随着同步辐射发展起来的独特技术,是研究材料局域原子结构和电子结构的一种重要方法。相比于X射线衍射,XAFS仅仅对于吸收原子周围局域结构敏感,样品可以是固体、液体甚至是气体。概述了XAFS的基本原理及几种常用的实验方法,结合上海光源的XAFS光束线站成果,介绍了近年来不同XAFS方法在催化、能源、纳米和半导体等材料科学热门研究领域的最新进展,展示了目前XAFS方法在材料科学研究中所发挥的重要作用。最后根据国内同步辐射光源和相关XAFS研究方法的进一步发展,展望了XAFS技术在材料科学研究中的应用前景。     

编者按

正同步辐射技术是近年来兴起的一种先进的研究手段,利用高能电子统周运动产生的高能量、高亮度的X射线能够探究物质的内部结构信息。同步辐射光源的各条线站均有各自的特点及适合的应用领域。基于同步辐射的原位实验成为了理解材料的成分-工艺-结构-性能之间关系的有力武器。近年来,基于同步辐射的一些新的表征方法及应用也逐步涌现,     

高分辨三维成像原位试验机研制进展及应用

先进材料及结构的损伤表征和在役性能评价是重大装备研发与服役中的关键科学问题。目前,依托同步辐射大科学装置的X射线三维成像技术在金属材料细观损伤力学行为研究方面具有独特优势,而兼容于同步辐射光源相应光束线站的各类原位加载装置对材料内部微结构损伤演化的动态高分辨表征具有重要意义。简要介绍了国内外依托世界各大高性能光源的原位加载试验机研制进展与应用成果,重点阐述了可实现单向拉压、循环加载及具备极寒、高温、真空等样品环境的基于同步辐射X射线成像的原位加载装置的设计原理及结构特点。最后,结合第三代高能X射线三维成像技术特点、先进光源线站建设、高通量试验要求等,对材料原位加载条件下的高时空分辨率动态成像进行了展望,指出开发集拉伸、压缩、低周疲劳、高周疲劳和超高周疲劳加载机构于一体的多功能原位试验机是一项重要的工作。     

基于电子诱导脱附的气体解吸实验装置研究

电子诱导脱附是指荷能电子轰击吸附了气体分子的材料表面,使得气体分子解吸出来的现象。在同步辐射光源、热阴极电离规和真空微电子器件等部件中,上述脱附气载是影响系统真空度和阴极寿命的主要因素。本文以日本光子工厂电子诱导脱附(KEK-ESD)装置试验数据为参考,研制了一台在150e V～1000e V电子能量范围内测量材料电子解吸系数的试验装置,并同KEK-ESD无氧铜材料试验数据进行了对比,证明本装置能有效测试材料表面的电子解吸系数。     

同步辐射成像技术在金属材料研究中的应用

金属材料作为一类重要的结构和功能材料,在人类社会发展中一直发挥着重要的作用。研究者也一直通过多种表征技术来研究金属材料的微观组织与性能。然而,金属材料的不透明特性在很大程度上限制了研究者们对其进行实时动态表征。随着第三代同步辐射光源的发展,同步辐射成像技术以其强穿透性、高时空分辨率、无损、可视化等优势在金属材料研究领域具有显著的优越性。回顾了金属材料实时原位研究工作的发展历程,简要介绍了近十多年来同步辐射二维/三维成像技术在金属凝固行为(晶粒生长、溶质扩散等)与物理场(电场、磁场和超声场)调控、材料内部微观组织结构(枝晶、金属间化合物形貌演变,析出相空间分布等)、细观损伤行为(裂纹的萌生、扩展及断裂机制)等研究中的典型应用,展望了同步辐射光源及成像技术的发展趋势及此技术在金属材料领域应用的未来前景。     

6～70keV同步辐射X射线能量标定

为建立高注量率同步辐射X射线计量领域相关的国家标准,对同步辐射X射线能量标定方法进行研究。在北京同步辐射装置上选择6、10和20keV三个能量点进行实验,得到的传递探测器校准因子与辐射能量的关系曲线近似直线,变化趋势呈线性递减;在20keV能量点,不同直径光阑条件下进行的标定实验验证了传递探测器的校准因子与光源照射到基准电离室与传递探测器的光子通量有关。在上海光源上进行10～70keV能量标定实验,得到传递探测器的校准因子拟合曲线;10～20keV能量段的变化趋势与在北京同步辐射装置得到的校准因子变化趋势一致,30～70keV能量段的校准因子随着能量的增加而平稳缓慢增大。对各个能量点标定产生的A类不确定度进行评定,为后续建立国家计量标准同步辐射X射线空气比释动能量值传递体系提供了技术数据。     

晶体材料微观结构的同步辐射白光劳厄微衍射研究

伴随着特种聚焦镜的出现和同步辐射技术的发展,利用微聚焦的同步辐射多波长X射线进行白光劳厄微衍射成为可能。通过白光劳厄微衍射实验,可以对材料局域微观结构进行无损定量表征,并建立材料的微观特性与机械性能之间的关系。脆性多晶Nd_2Ir_2O_7材料及激光3D打印的镍基高温合金材料的研究,体现了同步辐射白光劳厄微衍射技术在研究非均一的多相多晶材料的晶体取向、晶格畸变、缺陷类型和密度等重要微观结构信息方面的特点与优势。随着数据采集和数据分析的飞跃式发展,即使以微小的步长对样品上一个较大的区域进行劳厄微衍射实验,也可以近乎实时的获得晶体材料微观结构的定量图像。同步辐射白光劳厄微衍射发展至今已有20多年,并且新的同步辐射纳米衍射线站正在全世界范围内建设和服役。简单概括了同步辐射白光劳厄微衍射其实验设施、当前应用、最新技术发展以及未来可能涉及的领域,并借此激励更多的中国学者利用同步辐射白光劳厄微衍射技术进行材料科学的研究。     

Automated segmentation of synchrotron radiation micro-computed tomography biomedical images using Graph Cuts and neural networks

Synchrotron Radiation (SR) X-ray micro-Computed Tomography (μCT) enables magnified images to be used as a non-invasive and non-destructive technique with a high space resolution for the qualitative and quantitative analyses of biomedical samples. The research on applications of segmentation algorithms to SR-μCT is an open problem, due to the interesting and well-known characteristics of SR images for visualization, such as the high resolution and the phase contrast effect. In this article, we describe and assess the application of the Energy Minimization via Graph Cuts (EMvGC) algorithm for the segmentation of SR-μCT biomedical images acquired at the Synchrotron Radiation for MEdical Physics (SYRMEP) beam line at the Elettra Laboratory (Trieste, Italy). We also propose a method using EMvGC with Artificial Neural Networks (EMANNs) for correcting misclassifications due to intensity variation of phase contrast, which are important effects and sometimes indispensable in certain biomedical applications, although they impair the segmentation provided by conventional techniques. Results demonstrate considerable success in the segmentation of SR-μCT biomedical images, with average Dice Similarity Coefficient 99.88% for bony tissue in Wistar Rats rib samples (EMvGC), as well as 98.95% and 98.02% for scans of Rhodnius prolixus insect samples (Chagas's disease vector) with EMANNs, in relation to manual segmentation. The techniques EMvGC and EMANNs cope with the task of performing segmentation in images with the intensity variation due to phase contrast effects, presenting a superior performance in comparison to conventional segmentation techniques based on thresholding and linear/nonlinear image filtering, which is also discussed in the present article.     

Recent Activities of TIPC on Cryogenic Systems Used for Superconducting Accelerators in China

With the requirement of higher beam energy and luminosity, the cryogenic technologies are applied more and more widely in accelerator facilities. As a main research entity on cryogenics in China, Technical Institute of Physics and Chemistry (TIPC) makes significant contributions to the construction of cryogenic systems for several superconducting accelerators in China, i.e. the upgrade of the Beijing Electron-Positron Collider (BEPCII), the Shanghai Synchrotron Radiation Facility (SSRF) and the Peking University Free-Electron Laser Facility (PKU-FEL). In this paper the cryogenic systems for BEPCII, SSRF and PKU-FEL are introduced briefly, and our recent activities for these accelerators are described.     

非蒸散型吸气剂对混合气体的抽气行为研究

NEG抽除混合气体的行为不同于抽单纯气体.测试了SEAS公司的NEG组件ST707WP 1250对由80%H2和20%CO组成的混合气体的抽气性能,并和抽纯气性能进行了比较.混合气体中的NEG对H2的抽速受CO影响,随H2吸气量的增加而明显下降.混合气体中的NEG对CO的抽速不受H2影响.研究结果为SSRF储存环真空系统设计提供了重要依据.     

BENT — A software for raytracing of X-rays on bent oblique cut crystals

A software BENT is designed for raytracing of synchrotron radiation (SR) on bent oblique cut crystals. In this software, the SR source data can be generated by other existing software such as SHADOW [B. Lai and F. Cerrina, Nucl. Instr. and Meth. A246 (1986) 337.], and the image data after raytracing by BENT is arranged in the same way as is done by SHADOW. So analysis and continued tracing by SHADOW can be performed. The software BENT is used in designing the oblique cut bent crystal monochromator of the 4W1C beamline at the Synchrotron Radiation Laboratory, BEPC. Some of the results are presented.     

Synchrotron radiation-based irradiance calibration from 200 to 400 nm at the Synchrotron Ultraviolet Radiation Facility III

A new facility for measuring irradiance in the UV was commissioned recently at the National Institute of Standards and Technology (NIST). The facility uses the calculable radiation from the Synchrotron Ultraviolet Radiation Facility as the primary standard. To measure the irradiance from a source under test, an integrating sphere spectrometer-detector system measures both the source under test and the synchrotron radiation sequentially, and the irradiance from the source under test can be determined. In particular, we discuss the calibration of deuterium lamps using this facility from 200 to 400 nm. This facility improves the current NIST UV irradiance scale to a relative measurement uncertainty of 1.2% (k=2).     

聚硅氧烷基纳米多孔薄膜双分形结构的同步辐射小角X射线散射分析

以聚硅氧烷基材料为预聚体,采用两种核壳型致孔剂,以旋涂工艺分别制备两组聚硅氧烷基纳米多孔薄膜,采用北京同步辐射装置(BSRF)光源进行了小角X射线散射测试,在掠入射模式(入射角αi=0.2°)下得到了两组不同孔隙率纳米多孔薄膜的二维散射数据,在此基础上分析了薄膜的分形特征,发现所制备的薄膜除试样A1外,均存在双分形结构...     

Ultraviolet radiometry with synchrotron radiation and cryogenic radiometry

The combination of a cryogenic radiometer and synchrotron radiation enables detector scale realization in spectral regions that are otherwise difficult to access. Cryogenic radiometry is the most accurate primary detector-based standard available to date, and synchrotron radiation gives a unique broadband and continuous spectrum that extends from x ray to far IR. We describe a new cryogenic radiometer-based UV radiometry facility at the Synchrotron Ultraviolet Radiation Facility II at the National Institute of Standards and Technology. The facility is designed to perform a variety of detector and optical materials characterizations. The facility combines a high-throughput, normal incidence monochromator with an absolute cryogenic radiometer optimized for UV measurements to provide absolute radiometric measurements in the spectral range from 125 nm to approximately 320 nm. We discuss results on photodetector characterizations, including absolute spectroradiometric calibration, spatial responsivity mapping, spectroreflectance, and internal quantum efficiency. In addition, such characterizations are used to study UV radiation damage in photodetectors that can shed light on the mechanism of the damage process. Examples are also given for UV optical materials characterization.     

Fast microwave detection system for coherent synchrotron radiation study at KEK: Accelerator test facility

A fast room temperature microwave detection system based on the Schottky Barrier-diode detector was created at the KEK ATF (Accelerator Test Facility). It was tested using Coherent Synchrotron Radiation (CSR) generated by the 1.28 GeV electron beam in the damping ring. The speed performance of the detection system was checked by observing the CSR from a multi-bunch (2.8 ns bunch separation time) beam. The theoretical estimations of CSR power yield from an edge of bending magnet as well as new injection tuning method are presented. A very high sensitivity of CSR power yield to the longitudinal electron distribution in a bunch is discussed.     

Influence of the Vertical Emittance on the Calculability of the Synchrotron Ultraviolet Radiation Facility

A method to include the influence of the vertical electron beam emittance onto the calculability of synchrotron radiation is introduced. It accounts for the finite vertical size and angular spread of the electron beam through a convolution procedure. The resulting angular spread of synchrotron radiation can differ significantly from the ideal Schwinger result, depending on the conditions. For the Synchrotron Ultraviolet Radiation Facility detailed results on the influence of the electron emittance for total power and polarization calculations are presented.