共查询到20条相似文献,搜索用时 140 毫秒
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基于高斯谢尔光束的相干模式分解理论和波动光学,建立了部分相干同步辐射硬X射线光束通过光学器件的传播模型。模拟了微聚焦X射线光束照射下光栅的分数塔尔博特效应,得到了聚焦光束的光强分布和相干特性变化,并分析了散焦光束入射下的光栅自成像。然后通过模拟准直光束入射下的光栅塔尔博特效应,得到了不同传播距离处自成像条纹的变化情况,分析了影响光栅自成像条纹形状的因素。通过光栅衍射条纹测量同步辐射相干度,发现对矩形相位光栅来说,应该对衍射图样进行傅里叶分解,求出各级傅里叶系数随传播距离的变化曲线,从而得到入射光束相干特性。 相似文献
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本文依据软X射线标量散射理论,给出了一种用软X射线全积分散射检测超光滑表面粗糙度RMS值的方法,并设计和建立了测试装置,得到了新的测量结果 相似文献
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《中国光学》2019,(3)
研究X射线散射法在软X射线掠入射望远镜反射镜的表面粗糙度测量中的应用。首先,在光滑表面近似和细光束条件下,根据Harvey-Shack表面散射理论得出反射镜的面形仅影响总反射光分布中的镜向部分,对散射部分的影响可以忽略不计;然后设计了X射线散射法测量Wolter-I型软X射线掠入射望远镜的表面粗糙度的实验方案,并且对引起系统误差的主要因素进行了分析,确定了进行仿真实验时的参数;最后用Zemax对实验方案进行了仿真。在空间频率高于28/mm时,表面粗糙度的仿真测量结果与真值吻合得非常好。本文研究结果显示:在光滑表面近似和细光束条件下,反射镜的面形仅影响表面粗糙度的低频部分的测量准确性,对高频部分测量准确性的影响可以忽略不计,利用X射线散射法可以准确测量软X射线掠入射望远镜的表面粗糙度。 相似文献
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对金属表面热红外偏振特性的模型进行了研究,在建模中不仅考虑了金属表面的统计特性,也考虑了特别粗糙的金属表面存在的遮蔽效应问题.通过计算机模拟出不同表面粗糙度的金属板热红外偏振度和金属表面热红外辐射角之间的关系曲线,并和实验获得的结果进行了对比.对于表面粗糙度为1.6um的较为光滑的金属表面,模拟的结果基本吻合了实验中获得的数据.对于表面粗糙度为6.8um的较为粗糙的金属表面,仿真出的结果和实验中获得的数据相差较大.但在考虑了遮蔽效应后,模型模拟的结果得到了很大的改善.通过对模型的研究.分析确定了对金属板表面热红外偏振度影响的主要因素. 相似文献
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采用粒子模拟研究方法,利用PEGASUS 程序对等离子体环境下面向等离子体部件的沉积特性进行了模拟研究。结果显示部件表面连接缝隙尺寸、表面粗糙度、粒子入射的角度以及流量对沉积影响显著。在能量较小、溅射可忽略时,能量对沉积的影响很小。粗糙度越小,沉积量越小;同一种粗糙度,不同轮廓也会使沉积发生较大变化,轮廓一致的更有利于减小沉积。该模拟对研究等离子体与材料相互作用,分析瓦片缝隙尺寸、瓦片加工工艺和等离子体参数对面向等离子体部件沉积行为的影响具有重要意义。 相似文献
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由于沙地通常处在半干旱地区,在风蚀作用下表面结构特征会有所改变,同时,沙地表面粗糙度与组成成分的时间与空间变化也是研究风蚀模型所必须的输入信息。作为一种非接触的探测手段,遥感技术有助于实现对沙地表面粗糙程度在时空尺度上的研究。为了利用反射特性描述沙地表面结构特征,以人为模拟的粗糙沙地表面为研究对象,基于野外实测多角度高光谱反射信息,分析了沙地表面粗糙度变化对反射信息分布的影响,并且结合双向反射模型,试图利用模型参数反演粗糙度特征。通过研究发现,如果按照入射方向与沙地表面沙垄方向分类来看,与入射方向平行或者垂直均会对沙地表面反射分布特性有所改变。当沙垄方向与入射光方向垂直时,会使后向散射的反射峰值增加;而沙垄方向与入射光平行时,会使后向散射峰值向主平面两侧扩张。双向反射模型可以模拟沙地表面的反射特性,根据模型参数的变化也可以表示出沙地表面的粗糙度变化特性。这表明双向反射信息可以用于量化沙地表面结构特征,而且有助于了解结构特征对沙地光学特性的影响,也为研究颗粒介质固有光学特性以及反演沙地表面结构特征提供依据。 相似文献
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基于分形几何学,研究了表面粗糙度的分形特征.采用Weierstrass- Mandelbrot函数对多尺度自仿射的表面粗糙度进行了描述;建立了微通道内层流流动的三维模型并对表面粗糙度的影响进行了数值模拟,分析了雷诺数、相对粗糙度和分形维数对流动阻力特性的影响.研究结果表明,与常规尺度通道不同,粗糙微通道的Poiseuille数不再是常数,而是随雷诺数近似线性增加;相对粗糙度越大,流动产生的回流和分离所导致的流动压降越明显.在相同的相对粗糙度下,粗糙表面的分形维数越大,表面轮廓变化就越频繁,这也将导致流动阻
关键词:
粗糙度
层流阻力系数
微通道
分形 相似文献
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The calculation of reflection‐mode grazing‐incidence X‐ray absorption spectra from single surfaces and (multi‐)layered systems is studied here. In particular, the influence of the surface and interface roughness was investigated in detail. Simulations of grazing‐incidence reflection‐mode EXAFS spectra using a simple Fresnel theory neglecting any effect of roughness are compared with the Névot–Croce model and the elaborated distorted‐wave Born approximation which both include surface and interface roughness. Data are presented for clean gold surfaces, where the strong influence of the surface roughness on the resulting spectra is demonstrated. Furthermore, in the case of layered systems, the influence of both the outer (air or vacuum side) surface roughness and the inner interface roughness on the reflection‐mode EXAFS spectra is evaluated. The practical consequences of the observed correlations are discussed, and a quantitative data analysis of a copper sample that was oxidized in ambient air for several months is shown, including the evaluation of specular reflectivity profiles at fixed energy. 相似文献
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利用高斯-谢尔光源模型理论与交叉谱密度函数在自由空间传输的规律, 研究了上海同步辐射装置波荡器光源(BL15U)的空间相干性; 讨论了预聚焦镜、单色器对光束空间相干性的影响;实验测量了单色光狭缝S2处光束的横向相干长度(Z方向). 理论计算表明, S2处光束的横向相干长度为66.5 μm,但实验测量结果为27 μm. 理论与实验相差较大的原因是由于S2上游光学元件预聚焦镜或单色器周期性高频振动导致了光束空间相干性的退化.实验结果表明,上海同步辐射装置波荡器光源已有较强的空间相干性, 可以满足微米尺度的硬X射线相干性实验. 相似文献
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Harry Westfahl Jr Sérgio A. Lordano Luiz Bernd C. Meyer Florian Meneau 《Journal of synchrotron radiation》2017,24(3):566-575
In this work the coherence properties of the synchrotron radiation beam from an X‐ray undulator in a fourth‐generation storage ring are analyzed. A slightly focused X‐ray beam is simulated using a wavefront propagation through a non‐redundant array of slits and the mutual coherence function is directly obtained and compared with the Gaussian–Schell approximation. The numerical wave propagation and the approximate analytical approaches are shown to agree qualitatively, and it is also shown that, when the coherent fraction is selected by a finite aperture before the focusing element, even achromatic focusing systems like total reflection mirrors become slightly chromatic. This effect is also well accounted for in the Gaussian–Schell model. The wavefront propagation simulation through the non‐redundant array was repeated with an imperfect mirror demonstrating that, although the wavefront is distorted, its coherent length is practically unchanged. 相似文献
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L. Alianelli K. J. S. Sawhney M. K. Tiwari I. P. Dolbnya R. Stevens D. W. K. Jenkins I. M. Loader M. C. Wilson A. Malik 《Journal of synchrotron radiation》2009,16(3):325-329
The unprecedented brilliance achieved by third‐generation synchrotron sources and the availability of improved optics have opened up new opportunities for the study of materials at the micrometre and nanometre scale. Focusing the synchrotron radiation to smaller and smaller beams is having a huge impact on a wide research area at synchrotrons. The key to the exploitation of the improved sources is the development of novel optics that deliver narrow beams without loss of brilliance and coherence. Several types of synchrotron focusing optics are successfully fabricated using advanced miniaturization techniques. Kinoform refractive lenses are being developed for hard X‐ray beamlines, and the first test results at Diamond are discussed in this paper. 相似文献
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Experiments using a simple X‐ray interferometer to measure the degree of spatial coherence of hard X‐rays are reported. A monolithic Fresnel bimirror is used at small incidence angles to investigate synchrotron radiation in the energy interval 5–50 keV with monochromatic and white beam. The experimental set‐up was equivalent to a Young's double‐slit experiment for hard X‐rays with slit dimensions in the micrometre range. From the high‐contrast interference pattern the degree of coherence was determined. 相似文献
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在偏振光条件下,物体的表面反射受到折射率、表面粗糙度、入射角等多种因素的影响。针对粗糙物体表面在不同波段光照下表现出不同的偏振反射特性,提出一种基于Kirchhof理论的偏振光谱BRDF模型。利用已知材质在不同波长下的复折射率,对其折射率和消光系数部分分别反演出的对应光谱模型,进而得到复折射率的光谱模型;同借鉴经典的表面粗糙度测量方法,结合菲涅耳反射公式,推导出表面粗糙度的光谱模型,将得到的复折射率和粗糙度光谱模型与BRDF模型相结合,推导出偏振光谱BRDF建模。模型分别在折射率随波长变化、粗糙度为常量,折射率、粗糙度均随波长变化以及原模型三种情况下进行仿真对比实验,并将所得到的数据与其他资料进行对比。其结果表明,该模型能够较为准确的反映物体表面的偏振反射特性,并且能够描述偏振度随波长变化趋势的光谱特征,能够为偏振遥感、物质分类等方面的应用提供可靠依据。 相似文献
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Serkan Sahin 《Optics Communications》2010,283(22):4512-4518
An active bistatic LIDAR system operating through atmospheric turbulence is considered. Illumination field is assumed to be an electromagnetic Gaussian-Schell model beam. Target surface is modeled as a combination of isotropic phase screen governed by Gaussian statistics, to account for its roughness, and a Gaussian lens to account for its size and radius of curvature. With the help of a recently developed tensor method for propagation of stochastic electromagnetic beams through ABCD systems and random media we examine the evolution of states of coherence and polarization of the beam. In the case of unresolved flat (planar) target we show that by comparing coherence and polarization properties of the illumination beam and of the return beam it is possible to predict the typical roughness of the target surface. 相似文献
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D. Lützenkirchen‐Hecht R. Wagner S. Szillat A. K. Hüsecken K. Istomin U. Pietsch Ronald Frahm 《Journal of synchrotron radiation》2014,21(4):819-826
The layout and the characteristics of the hard X‐ray beamline BL10 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA are described. This beamline is equipped with a Si(111) channel‐cut monochromator and is dedicated to X‐ray studies in the spectral range from ~4 keV to ~16 keV photon energy. There are two different endstations available. While X‐ray absorption studies in different detection modes (transmission, fluorescence, reflectivity) can be performed on a designated table, a six‐axis kappa diffractometer is installed for X‐ray scattering and reflectivity experiments. Different detector set‐ups are integrated into the beamline control software, i.e. gas‐filled ionization chambers, different photodiodes, as well as a Pilatus 2D‐detector are permanently available. The performance of the beamline is illustrated by high‐quality X‐ray absorption spectra from several reference compounds. First applications include temperature‐dependent EXAFS experiments from liquid‐nitrogen temperature in a bath cryostat up to ~660 K by using a dedicated furnace. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface‐sensitive reflection‐mode experiments are presented. 相似文献