一种X射线聚焦光学及其在X射线通信中的应用

基于栅控脉冲发射X射线源与单光子探测技术的X射线通信已经实现了实验室语音通信验证,并对通信系统的误码率性能进行了分析,为探索未来X射线深空应用打下了坚实的基础.针对目前X射线通信面临的信号发散角大、通信距离短、难以实现工程化应用的情况,迫切需要对X射线通信天线系统进行深入研究.为了提高信号增益、增大X射线通信的距离,提出了多层嵌套式X射线聚焦光学作为X射线通信的"收发天线",理论分析了X射线聚焦光学用于X射线通信"收发天线"的可行性,分析了X射线聚焦光学的理论基础与结构设计,对"发射天线"发散角、"接收天线"有效面积与焦斑尺寸、信号增益等性能做了探讨.结果表明:在信号发射端,"天线"的发散角为3 mrad左右,发射增益23 d B;在信号接收端,"接收天线"的有效面积5700 mm2@1.5 keV,焦斑直径为4.5 mm,接收增益为25 d B,通信系统总的增益可达48 d B.     

微波反射特性测量实验的研究

利用普通微波分光仪研究微波的反射特性,能够测量出不同材料和不同厚度平板在不同入射角时对微波的反射强度.原理直观,物理规律明显,简单且实用.     

Comparison of focusing optics for femtosecond X-ray diffraction

We characterize and compare four different types of focusing optics for hard X-rays, suitable for femtosecond X-ray diffraction experiments, usinga tabletop femtosecond laser-based plasma source. We demonstrate a 23 μmfocus with a toroidally bent Ge single crystal. A maximum flux of 7× 10⁸ photons/(s mm²) is generated in a 32 μm focus using a multi-layer mirror. An elliptical glass capillary yields the highest number of photons per Bragg angle [2× 10⁵ photons/(s mrad)]. The largest number of photons[3× 10⁶ photons/s] per second is obtained in the 105 μm focus of a poly-capillary optical lens system. All numbers are given for characteristic Cu K _α photons.This revised version was published online in May 2005. The Article Category was removed.This revised version was published online in August 2005 with a corrected cover date.     

Accuracy design of ultra-low residual reflection coatings for laser optics

Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity(the degree of inhomogeneous is between -0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.     

Precision X-ray optics for fundamental interactions in atomic physics,resolving discrepancies in the X-ray regime

Reliable knowledge of the complex X-ray form factor (Re(f) and f) is required for many fields including crystallography, medical diagnosis and XAFS studies. However, there are discrepancies between theory and theory, experiment and experiment and theory and experiment of 10% and more, over central X-ray energies. Discrepancies exist for most elements, despite claimed experimental accuracies of 1%. This paper summarises the current variation between experimental and theoretical results, and outlines key issues for obtaining experimental accuracies of 1% in critical wavelength ranges for selected elements to address these issues. This paper critically surveys available experimental data for attenuation coefficients and suggests a procedure for obtaining significantly higher accuracy measurements in the future.     

An optimized two crystal arrangement for X-ray optics

Modification of the Schwarzschild optics for applications in hard X-ray imaging is discussed. The conditions necessary to achieve a high spatial resolution with two toroidally bent crystals in the Bragg geometry are formulated, and the focusing properties of the system are numerically simulated using the ray tracing method. It is predicted that such a system could provide a spatial resolution considerably higher than the resolution of the presently available X-ray optics.     

X-ray spectroscopy diagnostics of a recombining plasma in laboratory astrophysics studies

The investigation of a recombining laser plasma is topical primarily because it can be used to simulate the interaction between plasma jets in astrophysical objects. It has been shown that the relative intensities of transitions of a resonance series of He-like multicharged ions can be used for the diagnostics of the recombining plasma. It has been found that the intensities of the indicated transitions for ions with the nuclear charge number Z _n ~ 10 are sensitive to the plasma density in the range N _e ~ 10¹⁶–10²⁰ cm^–3 at temperatures of 10–100 eV. The calculations performed for the F VIII ion have determined the parameters of plasma jets created at the ELFIE nanosecond laser facility (Ecole Polytechnique, France) in order to simulate astrophysical phenomena. The resulting universal calculation dependences can be used to diagnose different recombining plasmas containing helium-like fluorine ions.     

Optimization of platinum-carbon multilayer mirrors for hard X-ray optics

The design of hard X-ray optics for astrophysical technology is one of the key technologies for investigating active galaxies and clusters of galaxies. In the present paper, we have optimized multilayer mirrors of platinum-carbon layer pairs for the hard X-ray region at different grazing angles. The Luus-Jaakola optimization procedure has been implemented for the global optimization of multialyer mirrors. With this algorithm it is not necessary to specify initially the number of layers present in a design.     

软 X射线光学表面散射检测

应用自行研制的软X射线反射率计,分别对不同的反射镜样品,在不同的工作波段以及掠射角下研究了软X射线波段掠入射光学表面的散射。实验结果表明：掠射角增加,波长减小,粗糙度增加,软X射线掠入射表面散射程度加重。     

Highly charged ions in a new era of high resolution X-ray astrophysics

X-ray astronomy and ground-based atomic physics have a long history of fruitful collaboration: Sound understanding of the underlying atomic physics is the key to reliable interpretation of the spectra from celestial sources; conversely, astronomical spectra have been used to benchmark and advance atomic physics. This interplay is about to become even more important as we enter a new era of high-resolution X-ray astrophysics with large effective collection area. Although high-resolution observations with the gratings on the Chandra and XMM-Newton observatories continue to drive new science, upcoming planned and proposed missions will open up new discovery space in the near future that is currently challenging to access: high-resolution spectroscopy on extended sources, in the Fe K band, and on short time scales. This review summarizes open questions in these areas and the design parameters for the Hitomi, XRISM, Athena, and Arcus observatories. The expected high quality of spectra taken with these observatories puts new constraints on the accuracy of atomic reference data required to take full advantage of the diagnostic potential of these spectra.     

Characterization of ion-exchanged glasses for application in integrated optics

The characterisation of a commercial alumino-silico-borate Na⁺ containing glass used as substrate in the fabrication of optical wave-guides is investigated. For that purpose, we have carried out conductivity measurements on samples with different substitution ratios using impedance spectroscopy. The samples were obtained by the ion exchange technique in NaNO₃/AgNO₃ molten salts at 370 °C (15 to 30 days), and after this exchange annealed for several days in order to obtain homogeneous samples. The electrical measurements, evidencing the so-called ‘mixed alkali effect’, combined with the Nernst-Einstein relationship give access to an experimental law of interdiffusion variation with composition. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Coding of functions by classes for numerical simulation in hard X-ray optics

An advantage of implementation of object-oriented programming principles in numerical simulation in hard X-ray optics was considered. The suggested approach was demonstrated on the example of two-beam X-ray interferometer with the refracting prism. It was shown that the proposed coding technique significantly simplifies the main program code by reducing its size, as well as making it more readable and easily modifiable.     

Investigation of ultra-short-period W/C multilayers for soft X-ray optics

Ultra-short-period W/C multilayers having periodic thickness range of 1.15-3.01 nm have been fabricated for soft X-ray optics using the high vacuum direct current (DC) magnetron sputtering system.     

Beta-delayed neutron spectra for application in reactor technology,nuclear physics and astrophysics

Recent developments in ß-delayed neutron (DN) spectroscopy are reviewed, and the importance of DN energy spectra for various problems in reactor physics, nuclear physics and astrophysics is discussed.     

The simulation of soft X-ray optics by ray-tracing

The ray tracing program for soft X-ray optics simulation is presented. This program can be used to study X-ray imaging property, energy transportation and concentration of X-ray beams by various X-ray optics. As an example, the results of the simulation about imaging characteristics of the toroidal mirror are given.     

Critical angles of X-ray scattering in total reflection

The critical angles of Compton and fluorescent scattering in total reflection of X-rays are found to have a common value and to be the same as that of mirror reflection.     

On the theory of X-ray refractive optics: Exact solution for a parabolic medium

The exact solution is obtained for a propagator describing x-ray propagation through a refractive parabolic medium. Such a medium arises in compound many-element refractive x-ray lenses that are used in synchrotron radiation sources. The solution obtained allows one to analyze such lenses in detail to predict their operation in particular applications (beam focusing, microobject imaging, and Fourier transform).     

声速测量实验中界面反射问题的探讨

探讨在声速测量实验中,声波在发射器和接收器两个端面之间反向形成极大值的位置和条件,以及声波强度随距离变化的规律。这有利于学生正确实验和理解声波特性。