用同步辐射X射线研究材料结构

使用同步辐射X射线进行材料的散射、衍射和吸收实验要比用一般X射线源的实验能提供新的、更精确、更详细的结构信息。同步辐射实验技术已发展到经常用于解决材料结构问题广泛领域的阶段。本文评述了作为材料原子级结构研究的同步辐射X射线散射和吸收技术的新进展,描述了包括表面和界面结构、局域结构、晶体结构和晶体缺陷在内的某些结构研究新例子,也提及最新发展和展望。     

用同步辐射X射线研究材料结构

使用同步辐射X射线进行材料的散射、衍射和吸收实验要比用一般X射线源的实验能提供新的、更精确、更详细的结构信息。同步辐射实验技术已发展到经常用于解决材料结构问题广泛领域的阶段。本文评述了作为材料原子级结构研究的同步辐射X射线散射和吸收技术的新进展,描述了包括表面和界面结构、局域结构、晶体结构和晶体缺陷在内的某些结构研究新例子,也提及最新发展和展望。     

合肥光源的衍射光栅制备技术

正衍射光栅是合肥光源光束线中重要的分光元件。本文介绍伴随合肥光源而发展起来的衍射光学元件精密加工实验室衍射光栅制备技术及相关工作进展。一、引言合肥同步辐射装置是工作在真空紫外-软X射线波段的连续光源。在真空紫外-软X射线波段通常使用光栅单色器分光,将所需的单色光从同步辐射光源中分离出来。衍射光栅是合肥光源重要的色散元件。国家同步辐射实验室成立了光学组,并逐步发展成现在的衍射光学元件精密加工实验室,     

高压衍射实验中的同步辐射光束的定位

 应用同步辐射光源进行高温高压原位能量色散X射线衍射实验,入射X射线光束定位是关键。北京同步辐射实验室高压衍射站引入四刀光阑扫描系统,实现调光定位自动化,简化调光手续,提高实验效率,为高压衍射实验站的用户进行实验提供了方便。     

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。     

同步辐射高压衍射技术

同步辐射光源具有宽光谱、高亮度、高准直等优异性能,被广泛地用于高压科学研究。在依托同步辐射光源所发展的诸多高压研究手段中,X射线衍射是最基本的也是应用最多的实验技术之一。本文简单介绍了同步辐射光的独特性能和光源的基本构成,以及同步辐射光束线和实验站的基本概念。针对基于金刚石对顶砧(DAC)的高压X射线衍射技术,阐述了多种测试方法的原理和应用,包括粉末衍射、单晶衍射、多晶衍射、径向衍射、激光加温衍射以及快速加载衍射等。对北京同步辐射装置(BSRF)4W2高压衍射线站所提供的同步辐射光品质、X射线微聚焦能力、多种衍射方法以及新近发展的实验技术进行了较详细的描述,并展望了高能同步辐射光源(HEPS)的建设给高压科学研究带来的机遇。     

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.     

北京同步辐射装置X射线衍射实验站在材料科学研究中的应用

简述了北京同步辐射装置X射线衍射实验站的实验装置,工作性能.利用X射线衍射仪开展了非晶周期多层膜、半导体超晶格结构研究,测量了Si₃N₄材料残存应力微区分布.     

北京同步辐射装置新建的X射线小角散射站投入运行

北京同步辐射装置（BSRF）是利用同步辐射光源进行科学研究的装置、对社会开放的大型公用科学设施，是我国凝聚态物理、材料科学、化学、生命科学、资源环境及微电子等交叉学科开展科学研究的重要基地。随着小角X射线散射（SAXS）用户的增长。BSRF原有的小角X射线散射站与X射线衍射站分时使用、共享489A光束线已远不能满足需求，广大用户强烈要求新建一条小角X射线散射站。     

一款小角X射线散射原位测量专用简易样品加热装置

原位加热实验是同步辐射小角X射线散射领域的新热点。本文针对同步辐射小角X射线散射中需要加热并原位实时检测的实验而设计的一款样品简易原位加热专用装置,该装置主要由温控器、样品池、固定架组成,它具有结构简单、操作容易的特点。本文介绍该装置的基本结构、特点并采用该装置进行原位加热干燥褐煤实验,通过分析实验结果验证装置的可行性。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.