高压下的同步辐射能量色散粉末衍射

 同步辐射已经成为高压研究的一个非常理想的光源。在北京同步辐射装置（BSRF）上、结合金刚石对顶砧超高压实验技术建立起来的能量色散X射线粉末衍射系统,已用于物质状态方程和结构相变的研究。介绍了能量色散衍射方法,以及同步辐射原位测试过程。     

In situ observation of water distribution and behaviour in a polymer electrolyte fuel cell by synchrotron X‐ray imaging

In situ visualization of the distribution and behaviour of water in a polymer electrolyte fuel cell during power generation has been demonstrated using a synchrotron X‐ray imaging technique. Images were recorded using a CCD detector combined with a scintillator (Gd₂O₂S:Tb) and relay lens system, which were placed at 2.0 m or 2.5 m from the fuel cell. The images were measured continuously before and during power generation, and data on cell performance was recorded. The change of water distribution during power generation was obtained from X‐ray images normalized with the initial state of the fuel cell. Compared with other techniques for visualizing the water in fuel cells, this technique enables the water distribution and behaviour in the fuel cell to be visualized during power generation with high spatial resolution. In particular, the effects of the specifications of the gas diffusion layer on the cathode side of the fuel cell on the distribution of water were efficiently identified. This is a very powerful technique for investigating the mechanism of water flow within the fuel cell and the relationship between water behaviour and cell performance.     

The contribution of Neutron and synchrotron radiation topography to the investigation of first-order magnetic phase transitions

Neutron and white beam synchrotron topography have proved to be valuable and complementary tools for the investigation of the coexistence of magnetic phases in single crystals. Neutron topographs indicate unambiguously which phase occupies a given region of the sample, whereas synchrotron radiation topographs give information about the coexistence-related lattice distortion and the dynamics of the phase transition. A few examples illustrate these capabilities. 1) Helimagnetic-ferromagnetic coexistence was followed in Tb and MnP by varying either the magnetic field or the temperature. The observed interfaces appear to result from competition between the elastic and magnetostatic terms of the total energy, the last term being dominant in the field-driven case. 2) The reorientational transition of hematite was shown to correspond, when spread over a wide temperature range, to a succession of abrupt transitions, probably related to an inhomogeneous incorporation of small amounts of impurities during growth. A similar feature also explains the occurrence of small ferromagnetic islands which remain in the helimagnetic phase of Tb.     

同步辐射探测器的应用与发展

探测器是同步辐射实验的重要环节。探测器水平必须不断提高才能适应同步辐射发展的需求，最大限度地发挥先进光源为人类研究提供的强大支持作用。文章介绍了当前同步辐射实验中普遍使用的各种探测器的原理和特点，并就一些新型探测器的发展情况进行了阐述。     

Irradiation damage to frog inner ear during synchrotron radiation tomographic investigation

Unexpectedly severe radiation damage, showing up through deformation of the saccule, was encountered during a synchrotron radiation high-resolution (700 nm pixel size) tomographic observation of an inner ear, fixed in a formaldehyde solution, of the frog Rana esculenta. The visible displacement of the edge of the otoconia-filled part of the saccule amounted to about 100 μm after an irradiation with 20.5 keV X-ray photons corresponding to a dose of 1.5 kGy for the protein matrix. The close-knit coexistence of organic and mineral components in the biological tissue may be linked to the dramatic increase of radiation dosage sensitivity.     

同步辐射探测器的应用与发展

探测器是同步辐射实验的重要环节。探测器水平必须不断提高才能适应同步辐射发展的需求,最大限度地发挥先进光源为人类研究提供的强大支持作用。文章介绍了当前同步辐射实验中普遍使用的各种探测器的原理和特点,并就一些新型探测器的发展情况进行了阐述。     

Dynamical beats of forward-scattered resonant synchrotron radiation as a nuclear polariton effect

The decay of the nuclear exciton (immobile collective excitation), created by a pulse of synchrotron radiation, is analyzed. It is shown that in the later phases of the decay, the exciton becomes localized at the sample’s frontal surface. Inside the sample, the secondary gamma-quanta, emitted by the contracting exciton, are converted into polaritons (mobile nuclear excitations) characterized by different frequencies and equal group velocities. On the sample’s back surface, the polariton interference causes a beating structure of the transmitted radiation, observed in experiments.     

Light flux density threshold at which protein denaturation is induced by synchrotron radiation circular dichroism beamlines

New high‐flux synchrotron radiation circular dichroism (SRCD) beamlines are providing important information for structural biology, but can potentially cause denaturation of the protein samples under investigation. This effect has been studied at the new CD1 dedicated SRCD beamline at ISA in Denmark, where radiation‐induced thermal damage effects were observed, depending not only on the radiation flux but also on the focal spot size of the light. Comparisons with similar studies at other SRCD facilities worldwide has lead to the estimation of a flux density threshold under which SRCD beamlines should be operated when samples are to be exposed to low‐wavelength vacuum ultraviolet radiation for extended periods of time.     

甲胺分子的同步辐射光电离解离质谱

在超声射流冷却条件下,利用同步辐射光源,结合飞行时间质谱对CH3NH2分子在60—140nm波长范围内的光电离解离进行了研究.主要动力学过程为母体离子的解离过程.CH2NH2+和CH3+由CH3NH2+在高能量时解离生成,而CH2NH2+的1,1脱H2过程则产生其他离子.CH3NH2分子的电离势(IP)为916±001eV,和分子轨道能量计算的理论值符合得非常好,并获得CH3NH2+和CH2NH2+的生成热分别为860±05kJmol和7541kJmol. 关键词： 同步辐射光电离 飞行时间质谱 电离势 生成热     

利用虚光子和康普顿散射对同步辐射的分析

从虚光子的康普顿散射出发,给出了一种对同步辐射进行解释的新理论。当带电粒子在加速器中做圆周运动时,加速器的磁场可以看作周期静磁场,可以等效为虚光子。当该虚光子与加速器中运动的带电粒子发生康普顿散射时,就会转换为实光子辐射出去。给出了同步辐射实光子的波长的计算公式,并从合肥国家同步实验室和北京同步辐射装置的峰值特征波长以及斯坦福直线加速器中心的 Ec/ Ee3值、强磁场中子星极区的同步辐射等方面验证了该公式的正确性。     

利用同步辐射光电子能谱技术测量ZnO/PbTe异质结的能带带阶

异质结结构界面的能带带阶是一个非常重要的参数,该参数的精确确定直接影响异质结的光电性质研究以及异质结在光电器件上的应用.利用同步辐射光电子能谱技术测量了ZnO/PbTe异质结结构的能带带阶.测量得到该异质结价带带阶为2.56 eV,导带带阶为0.49 eV,是一个典型的类型I的能带排列.利用变厚度扫描的测量方法发现,ZnO/PbTe界面存在两种键,分别是Pb—O键(低结合能)和Pb—Te键(高结合能).在ZnO/PbTe异质结界面的能带排列中导带带阶较小,而价带带阶较大,这一能带结构有利于PbTe中的激发电子输运到ZnO导电层中.该类结构在新型太阳电池、中红外探测器、激光器等器件中具有潜在的应用价值.     

In situ observation of cascade damage under heavy ion irradiation

Abstract

Collision cascades initiated from high energy PKAs produce defect clusters in crystalline solids irradiated with fast neutrons or energetic ions. They will affect not only an early stage of microstructural evolution but that at high fluence by changing free defect survival rate. To elucidate fundamental processes of cascade damage evolution, in situ observation of microstructure in FCC metals under heavy ion irradiation has been carried out using a combined facility of a 400 kV accelerator and a 200 kV transmission electron microscope installed in the University of Tokyo, Tokai. Defect clusters produced by individual energetic ions are observed during irradiation to examine subcascade formation, interaction of point-defects from cascade damage and related point-defect processes.     

永磁扭摆磁铁的同步辐射特性和结构分析

简要分析了永磁扭摆磁铁所产生的同步辐射光的基本特性，并得出永磁扭摆磁铁所产生的同步辐射光的辐射功率角分布和总功率.介绍了永磁扭摆磁铁的基本结构，并对起主要承载力的C型框架和整体结构进行了有限元分析，从而得到磁铁结构在不同情况下的变形.应用理论公式对C型框架的变形位移量进行了验证，为永磁扭摆磁铁的结构设计和进一步改进提供了理论依据. 关键词： 扭摆磁铁 同步辐射 C型框架 有限元分析     

用同步辐射X射线衍射技术分析GaN/Si外延膜的结构与应变

选用有AlN和AlGaN缓冲层的GaN/Si作为测试样品,采用同步辐射X射线衍射(SRXRD)技术对样品外延膜(GaN)的几何结构、晶格常量及其应变进行了分析.结果表明,同步辐射X射线衍射实验可以作为一种有效的技术手段,测试固体结构及应变.     

In situ X‐ray data collection and structure phasing of protein crystals at Structural Biology Center 19‐ID

A prototype of a 96‐well plate scanner for in situ data collection has been developed at the Structural Biology Center (SBC) beamline 19‐ID, located at the Advanced Photon Source, USA. The applicability of this instrument for protein crystal diffraction screening and data collection at ambient temperature has been demonstrated. Several different protein crystals, including selenium‐labeled, were used for data collection and successful SAD phasing. Without the common procedure of crystal handling and subsequent cryo‐cooling for data collection at T = 100 K, crystals in a crystallization buffer show remarkably low mosaicity (<0.1°) until deterioration by radiation damage occurs. Data presented here show that cryo‐cooling can cause some unexpected structural changes. Based on the results of this study, the integration of the plate scanner into the 19‐ID end‐station with automated controls is being prepared. With improvement of hardware and software, in situ data collection will become available for the SBC user program including remote access.     

同步辐射纳米成像技术的发展与应用

伴随着相关技术的进步,X射线纳米成像方法近年来得到了长足的发展,并在能源材料、工业催化、生命科学和环境科学等多个科研领域中发挥着重要的作用。文章总结了同步辐射纳米成像技术的发展现状,并结合实例讨论了其在若干学科领域的前沿应用。在此基础上,作者强调了先进数据分析手段和科研大数据发掘等在多尺度、多维度X射线成像领域中所扮演的重要角色。希望通过文章将同步辐射纳米成像技术系统地介绍给读者,以期进一步发掘该技术的潜力,促进其在各个科研领域的应用和推广。     

三氯乙烯的真空紫外同步辐射光电离和光解离

利用真空紫外(VUV)同步辐射光源和反射式飞行时间质谱仪，在超声冷却条件下对三氯乙烯(C₂HCl₃)进行了光电离研究，通过测量各离子的光电离效率(PIE)曲线，得到了C₂HCl₃的电离势P_I(C₂HCl₃)=9.51±0.05eV，以及C₂HCl₃光解离碎片离子的出现势(P_A)：P_{关键词： 同步辐射光电离 电离势 出现势 三氯乙烯}     

从2009年诺贝尔化学奖看同步辐射装置和技术在生物化学研究中的重要作用

文章介绍了获得2009年诺贝尔化学奖的原核细胞核糖体结构解析的历程.在这个历时20年的探索过程中,同步辐射装置起到了重要的作用.同步辐射这种大型的科学装置为前沿的科学研究提供了不可缺少的支撑,文章通过核糖体结构解析的过程,阐述了这种支撑所具有的明显的地域特征.     

上海光源准直测量方案设计

上海光源在准直测量方案设计中面临的最大挑战来自于松软地基及高精度的定位要求。上海光源的准直过程分为控制网测量、元件标定、预安装准直、现场安装及平滑测量5个关键步骤。采用激光跟踪仪和静力水准系统等测量手段,将控制网精度设计为0.08 mm,其余步骤精度达到0.05 mm,以保证相邻共架机构的准直精度达到0.12 mm,优于0.15 mm的设计指标。方案在注重精度指标的同时,还兼顾了可靠性、测量效率、费用及实时监测的可能性。