Multilayer optics for XUV spectral region: technology fabrication and applications

We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography (ψ-13nm) and short period multilayer optics.     

基于布拉格反射镜的X射线多色单能成像谱仪

报道了一种基于布拉格反射镜的多色单能成像谱仪研制工作,谱仪由针孔阵列、布拉格反射镜和CCD相机组成.大约有300个微孔的针孔阵列板置于布拉格镜前用于空间成像,通过布拉格反射镜的单色化,投射到CCD上的数百个小孔成像沿色散方向获得了能量分辨.经过图像处理,可以还原得到目标的多色单能二维成像.根据采用的布拉格分光元件和图像还原方法,谱仪的能量分辨达到了50—200（λ/Δλ）;针孔成像的空间分辨优于10 μm.同时还为该谱仪开发了专门的单能图像重建软件及图像数据后处理软件,可以在任意选择的窄能带内还原准单能图像.并重点介绍了该谱仪的优化设计、获得的技术指标以及专门研制的超短周期（2.5 nm）X射线W/B₄C多层镜. 关键词： X射线光学 诊断技术 布拉格反射镜 X射线多层镜     

软X光多层膜位相型矩形光栅的实验研究及其光学特性

详细给出了软Ｘ光多层膜位相型矩形光栅的实验，分析测试结果以及在北京国家同步辐射实验室测得的光学衍射特性，并进行了分析。     

The characteristic X-ray spectra of free atoms of metals

The article presents the results of a study of characteristic X-ray spectra of free atoms by means of a new simple technique. A pulsed electron beam was used for evaporation and to create inner-shell vacancies in free atoms of metals. The spectra were obtained with the help of an X-ray monochromator which allowed precise comparison between the free-atoms spectra and corresponding solid-state spectra. The shifts of the peaks were measured and found to be in the range Δλ/λ≈10⁻⁵–10⁻⁴. The K-, L- and M-series spectra were studied. A number of the free-atoms spectra revealed structure which was not resolved in the solid-state spectra and which is of interest for atomic structure calculation applications. This electron beam technique for the investigation of X-ray characteristic spectra of free atoms can be used for the refinement of X-ray wavelength standards.     

13.9 nm马赫贞德干涉仪用软X射线分束镜研究

 介绍了13.9 nm马赫贞德干涉仪用软X射线分束镜的设计、制备与性能检测。基于分束镜反射率和透过率乘积最大的评价标准,设计了13.9 nm软X射线激光干涉实验用多层膜分束镜。采用磁控溅射方法在有效面积为10 mm×10 mm、厚度为100 nm的Si3N4基底上镀制了Mo/Si多层膜,制成了多层膜分束镜。利用X射线掠入射衍射的方法测量了Mo/Si多层膜的周期。用扩束He-Ne激光束进行的投影成像方法定性分析了分束镜的面形精度,利用光学轮廓仪完成了分束镜面形精确测量。利用北京同步辐射装置测量了分束镜反射率和透射率,在13.9 nm处,分束镜反射率和透过率乘积达4%。使用多层膜分束镜构建了软X射线马赫贞德干涉仪,并应用于13.9 nm软X射线激光干涉实验中,获得了清晰的含有C8H8等离子体电子密度信息的动态干涉条纹。     

1—4 MA电流驱动的丝阵X光辐射优化的实验研究

进行了1—4MA电流驱动的钨丝阵列负载的Z箍缩实验研究,通过丝阵参数、负载电极结构的优化设计及负载初始装配状态的控制优化X光辐射功率,在单、双层丝阵的内爆实验中分别获得5.3±1.0 TW和5.6±1.1 TW的峰值辐射功率,创同类装置上X光辐射功率的最高纪录. 关键词： Z箍缩')" href="#">Z箍缩 丝阵X光辐射 优化     

Advances in synchrotron hard X-ray based imaging

Modern synchrotron radiation (SR) sources have dramatically fostered the use of SR-based X-ray imaging. The relevant information such as density, chemical composition, chemical states, structure, and crystallographic perfection is mapped in two, or, increasingly, in three dimensions. The development of nano-science requires pushing spatial resolution down towards the nanoscale.The present article describes a selection of hard X-ray imaging and microanalysis techniques that emerged over the last few years, by taking advantage of the flux and coherence of the SR beams, as well as exploiting the advances in X-ray optics and detectors, and the increased possibilities of computers (memory, speed). Examples are given to illustrate the opportunities associated with the use of these techniques, and a number of recent references are provided. To cite this article: J. Baruchel et al., C. R. Physique 9 (2008).     

Hermite hyperbolic/sinusoidal Gaussian beams in ABCD systems

For a Hermite hyperbolic/sinusoidal Gaussian beam with focusing properties, passing through an arbitrarily shaped rectangular aperture on the source plane and an on-axis x–y asymmetric ABCD system, the receiver plane expression is derived using the Collins integral. The specific example of a single thin lens placed on the propagation path is examined at selected source, propagation and optical element parameters. Viewing the progress of the beam in propagation, we find that subjecting the source beam to an aperture will give rise to excessive spreading during propagation. The lens setup will act to concentrate the energy of the beam around its focal point as expected, while in some circumstances it will also execute beam profile changes. By adjusting the aperture opening in the shape of a narrow slit, the beam will become aligned in the opposite direction after propagating after having traveled sufficiently. The results are presented as intensity graphs in the form of contour plots and 3D illustrations.     

Asymptotic approach to the truncated cosh-Gaussian beams

The propagation behavior and M ²-factor of truncated cosh-Gaussian (ChG) beams are studied by using the asymptotic approach. Detailed numerical results are given to illustrate the dependence of M ²-factor on the beam decentered parameter , truncation fraction p and power fraction f. Our results are self-consistent and reduce to those of Pare and Belanger [Opt. Commun. 123, p. 679 (1996a); Proc. SPIE 2870, p. 104 (1996b)]. The advantage of the approach is shown, and the problems introduced by the hard-aperture diffraction and the approach used are discussed.     

超强激光超热电子激发的Kα X射线发射研究

建立了无色散型X射线谱仪. 利用SILEX-I激光装置的超强激光辐照固体物质,分别在靶前、后定量测量了Cu和Mo物质在不同激光功率密度时的X射线谱和Kα光子产额,推导了不同激光强度时的Kα X射线光子转换效率. 实验发现,打靶激光能量越高,靶后出射的Kα产额越高,100μm Mo靶可获得10^-5量级转换效率. 关键词： X射线发射 激光-物质相互作用 Kα谱仪')" href="#">Kα谱仪     

Decoherence within a single atom

An “almost diagonal” reduced density matrix (in coordinate representation) is usually a result of environment induced decherence and is considered the sign of classical behavior. We show that the proton of a ground state hydrogen atom can indeed possess such a density matrix. This example demonstrates that the “almost diagonal” structure may be derived from an interaction with a low number of degrees of freedom which play the role of the environment. We also show that decoherence effects in our example can only be observed if the interaction with the measuring device is significantly faster than the interaction with the environment (the electron). In the opposite case, when the interaction with the environment is significant during the measurement process, coherence is maintained. Finally, we propose a neutron scattering experiment on cold He atoms to observe decoherence which shows up as an additional positive contribution to the differential scattering cross section. This contribution is inversely proportional to the bombarding energy.     

Far-field intensity distribution, M factor of beams generated by Gaussian mirror resonator

We investigated M² factor and far-field distribution of beams generated by Gaussian mirror resonator. And we found usable analytical expressions of the M² factor and the far-field distribution intensity with respect to variation of diffraction parameters. Particular attention was paid to the parameters such as mirror spot size and reflectance of the Gaussian mirror.     

Some remarks on the dynamical systems approach to fourth order gravity

Building on earlier work, we discuss a general framework for exploring the cosmological dynamics of Higher Order Theories of Gravity. We show that once the theory of gravity has been specified, the cosmological equations can be written as a first-order autonomous system and we give several examples which illustrate the utility of our method. We also discuss a number of results which have appeared recently in the literature.     

Hyperfine structure operator in the tensorial form of second quantization

The general tensorial form of the hyperfine interaction operator in the formalism of second quantization is presented. Both diagonal and off-diagnonal matrix elements of the above-mentioned operator are found using an approach based on a combination of second quantization in the coupled tensorial form, angular momentum theory in three spaces (orbital, spin and quasispin) and a generalised graphical technique. This methodology allows us to account for correlation effects efficiently and, therefore, to study the hyperfine interactions in complex many-electron atoms, those with openf-shells included, in a practical manner. All this will lead us to design an efficient program for large scale calculations of hyperfine structure and isotope shift.     

On quantum iterated function systems

A Quantum Iterated Function System on a complex projective space is defined through a family of linear operators on a complex Hilbert space. The operators define both the maps and their probabilities by one algebraic formula. Examples with conformal maps (relativistic boosts) on the Bloch sphere are discussed.     

Collimation of atomic beams by resonant laser radiation pressure

The application of the resonant light pressure created by an axially symmetrical light field for collimating atomic beams has been considered. As an example, consideration is given to the possibility of collimating an atomic beam by the light field produced by the reflection of a plane wave from the internal surface of a metal cone. It has been shown that the radiation pressure can reduce the atomic-beam transverse velocities to the value of the order of 100 cm/s which corresponds to effective temperature of about 10^–3 K. A method for producing collimated beams of cold atoms based on simultaneous deceleration and collimation of atomic beams by resonant laser radiation pressure is proposed.