基于光栅衍射的晶体X射线衍射缺级的理论基础和实验研究

以光栅衍射缺级理论为切入点对晶体X射线衍射缺级的现象、产生的根源进行了理论分析,得出：(1) 晶体X射线衍射缺级存在的可能性在于某些晶体材料晶胞的几何结构因子为零;(2) 在复式格子晶体或具有某种特殊缺陷的晶体的X射线衍射图样中存在缺级是这方面实验研究的方向。这些结论在材料物相、材料结构类型和不完整性分析等方面具有一定的参考价值。     

Intensity Distribution of the Three-Wave Diffraction from Dislocation Epitaxial Layers in the Reciprocal Space

The three-wave X-ray diffraction in strongly disordered epitaxial layers of GaN and ZnO is experimentally investigated. The charts of the intensity distribution in the reciprocal space are plotted in coordinates q_θ and q_? for the most intensive three-wave combination (1010)/(1011) by means of subsequent θ- and ?-scanning. A nontrivial shape of the θ-sections of these contours at a distance from the ? center of reflection is revealed; it is different for different samples. For the θ-curves at the center of reflection, we observed a common peak that may be approximated by the Voigt function with a power-low decrease in the intensity at the wings; the decrease law (from–4.5 to–5.0) is found to be considerably greater than that for the similar curves of two-wave diffraction and not depending on the dislocation density and distribution in layers. In some films we observed a coarse-block structure; in addition, it follows from the distribution in the reciprocal space that these blocks are turned with respect to each other around a normal to the surface, which allows us to suggest the existence of low-angle boundaries between them, consisting exclusively of edge dislocations.     

Formation of Spectral Valleys in the Hard X-Ray Spectrum by Diffraction Band Reject Filtering

JETP Letters - The possibility of forming deep spectral valleys in the polychromatic spectrum of X rays with an energy of E ≥ 15 keV using diffraction band rejection is demonstrated....     

Dynamical Theory of X-Ray Diffraction in a Crystal with a Surface Grating of Another Material

Journal of Experimental and Theoretical Physics - A general theory is developed for dynamical X-ray diffraction in a crystal on the surface of which a lateral periodic structure of thin-film lines...     

Spectral and Angular Dependences of the Efficiency of Three-Layer Relief-Phase Diffraction Elements of the IR Range

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 ≤ λ ≤ 5 μm) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem.     

红外光谱法及单晶X衍射法研究Fe(Ⅲ)水解形态分布

采用Fe-Ferron逐时络合比色法研究了聚铁絮凝剂中不同pH值的Fe(a),Fe(b),Fe(c)的稳定性。结果表明,Fe(b)不稳定,10～15 d后全部转化为Fe(c),Fe(c)的含量经10～15 d后趋于稳定,Fe(a)的含量10 d后也趋于稳定。采用常温长时间结晶法从Fe(Ⅲ)-SO2-₄水溶液中制备出了单晶,并用红外光谱法及单晶X射线衍射法研究了所得单晶的结构。研究显示,从低pH值(pH 0.5左右)的Fe(Ⅲ)溶液中所得单晶中没有Fe—OH—Fe基团、Fe—OH基团、Fe的二聚羟基络合基团,仅为Fe(Ⅲ)离子形态的单晶,以氨水为碱化剂时其单晶化学式为Fe(H₂O)₆ (SO₄)₂NH₄·6H₂O。采用常温长时间结晶法,随水分的不断蒸发,不同初始pH值及不同碱化剂的Fe(Ⅲ)溶液一般都在pH 0.5左右结晶,还由于铁盐水解形态不稳定等原因引起。在低pH值下难以得到Fe(Ⅲ)的羟基络合物或聚合体单晶。实验研究显示,在絮凝剂水解形态研究中,红外光谱法、单晶X射线衍射法均有良好的应用前景。     

X射线衍射法在泌尿系结石研究中的应用

泌尿系结石是一种世界范围的常见病、多发病。准确分析尿石的化学成分和物相,有助于了解泌尿系结石的形成机制。X射线衍射法(XRD)是进行泌尿系结石研究的最重要方法之一,用作定性分析时具有可靠性,用作定量分析时具有准确性,且检测简便迅速、灵敏度高、多组分和多晶态可一次性检测。文章综述了XRD在泌尿系结石定性和定量分析中的应用以及XRD与质子激发X射线发射光谱(PIXE)、X射线光电子能谱(XPS)和原子力显微镜(AFM)等联合分析尿石的研究进展。     

The Complexity Classes of Angular Diagrams of the Metal Conductivity in Strong Magnetic Fields

Journal of Experimental and Theoretical Physics - We consider angular diagrams describing the dependence of the magnetic conductivity of metals on the direction of the magnetic field in rather...     

在同步辐射软X射线能区硅光电二极管的自标定

在同步辐射软X光能区(50—2000eV)进行了硅光电二极管的自标定实验.因为消除了二极管的“死区”并采用很薄层的SiO₂作窗,使得可以用简单的模型来分析实验结果.由实验测得的光电流,计算出硅光电二极管的量子效率,并求得入射同步辐射的光通量.     

Instability of Solution of Phase Retrieval in Direct Diffraction Phase-Contrast Imaging with Partially Coherent X-Ray Source

The theoretical model of direct diffraction phase-contrast imaging with partially coherent x-ray source is expressed by an operator of multiple integral. It is presented that the integral operator is linear. The problem of its phase retrieval is described by solving an operator equation of multiple integral. It is demonstrated that the solution of the phase retrieval is unstable. The numerical simulation is performed and the result validates that the solution of the phase retrieval is unstable.     

Spectral and diffraction properties of microchannel plates in the long-wavelength X-Ray range

The spatial distribution of the intensity and spectra of X rays at the output of microchannel plates is studied both experimentally and theoretically. A model of planar antenna array is used for radiation transmitted through an ordered system of through hollow microchannels for the energy range of 90–2000 eV. The results of the calculations are in good agreement with experimental data obtained with the parallel beams of monochromatic synchrotron radiation. The energy characteristics of the output radiation whose fine spectral structure corresponds to the reflection and fluorescence spectra near the Si L- and Si K-absorption edges are presented.     

Diffraction Fields in the Focal Space of Symmetrical Hyperbolic Focusing Lens

The fields refracted by circular symmetric hyperbolic lens illuminated by a linearly polarized plane wave are calculated from the induced surface currents. It is shown that the fields in the axial region approximate to the fields in the aperture of corrugated horn under balanced hybrid condition. The image structures for different focal ratio are compared with the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. The coupling between the lens and a corrugated horn at different position on focal plane are presented. The lens resolution and pix numbers are evaluated.     

基于SR-WAXS技术的竹材纤维素晶胞模型研究

竹材中纤维素聚集态结构的不同,将直接影响到竹纤维复合材料性能,对于竹材纤维素晶胞单元的认识主要基于Meyer-Misch模型,由于天然纤维素的同质异构体,在每种植物中存在比例不同,所以竹材中纤维素应有其特有的晶胞模型。以毛竹(Phyllostachys edulis (carriere) J. Houz)为研究对象,通过同步辐射广角X射线散射技术对毛竹纤维素晶胞模型进行研究,利用单斜晶系晶面间距公式与毛竹纤维素衍射峰,精确计算晶胞模型。结果显示,若以b轴为纤维轴的单斜晶系纤维素单元,则晶胞参数为：a=8.35 ,b=10.38 ,c=8.02 ,β=84.99°,该晶胞包含四个葡萄糖基,由两条反向平行分子链构成。研究结果可为开发制作高性能竹纤维复合材料等高附加值应用提供理论依据。     

Demonstration of Mo Soft X-Ray Lasers with a Grazing Incidence Pumping Scheme in the XL-II Facility

A Ni-like Mo soft x-ray laser （SXRLs） operating at 18.9nm has been demonstrated by employing a grazing incidence pumping scheme with 120m^3 in the 200ps pre-pulse and 140mJ in the 200fs main pulse. The SXRL gain is estimated to be 1.5-3cm^-1 when a grazing incidence angle of 14° is applied. Numerical simulations are also performed to investigate the dynamics of the ion distribution. It is found that a high intensity at 2.4× 10^14 W/cm^2 of the 200fs main pulse could heat the pre-plasma rapidly to an appropriate temperature for population inversion, and could compensate for the shortage of the total pump energy to a certain extent.     

On the Transparency of Alkali-Halide Crystal in the Terahertz Spectral Range

Optics and Spectroscopy - The transmission of THz (to 3000 μm) radiation by alkali halide single crystals of sodium chloride (NaCl), potassium chloride (KCl), potassium bromide (KBr), and...     

XRD粉末衍射法研究微波场作用下4A分子筛的合成

在微波场作用下合成了粒度均匀、白度和钙离子交换容量高、性能优异的4A分子筛。用XRD粉末衍射法研究了硅铝比、水钠比、微波功率和微波加热时间对微波合成4A分子筛的影响,找出了在微波场作用下合成4A分子筛的最佳条件,并用IR, SEM和DSC等方法对合成的产物进行了表征。     

同步辐射X射线衍射光谱在地带性土壤粘粒矿物研究中的应用

X射线衍射(XRD)光谱是分析土壤粘粒矿物组成的重要手段,但常规XRD分析存在前处理复杂、耗时较长、光谱分辨率低、扫描不充分等问题.为此,该研究依托北京同步辐射装置(BSRF)的4B9A衍射实验站,以我国东部不同气候带(即温带、亚热带、热带)的7种地带性森林土壤(棕色针叶林、暗棕壤、棕壤、黄棕壤、黄壤、赤红壤和砖红壤)...     

微结构X射线源中电子与阳极作用的蒙特卡罗模拟

根据电子多重散射理论,基于蒙特卡罗方法研究不同能量电子垂直入射不同材料的阳极靶后,电子在阳极靶内的沉积能量分布,及X射线发射位置的能量分布.结果表明：电子在靶内的轨迹扩展和入射电子能量、靶材料有关,99%电子能量沉积在近似圆柱形区域内.且电子在入射方向上的沉积能量分布不是直接递减,而是先递增到一定深度后再递减,符合电子背散射理论.说明X射线产生区域是在距表面一定深度区域内.另外,通过对比分析发现金刚石膜作为电子吸收光栅是不可行的,但作为热沉材料有很大的潜力.这些结论可为微结构X射线源研究及高亮度高相干X射线源设计提供参考.     

Direct Numerical Simulation of the Rayleigh-Taylor Instability with the Spectral Element Method

A novel method is proposed to simulate Rayleigh-Taylor instabilities using a specially-developed unsteady three-dimensional high-order spectral element method code. The numerical model used consists of Navier-Stokes equations and a transport-diffusive equation. The code is first validated with the results of linear stability perturbation theory. Then several characteristics of the Rayleigh-Taylor instabilities are studied using this three-dimensional unsteady code, including instantaneous turbulent structures and statistical turbulent mixing heights under different initial wave numbers. These results indicate that turbulent structures of Rayleigh-Taylor instabilities are strongly dependent on the initial conditions. The results also suggest that a high-order numerical method should provide the capability of simulating small scale fluctuations of Rayleigh-Taylor instabilities of turbulent flows.