Fabrication of nested elliptical KB mirrors using profile coating for synchrotron radiation X-ray focusing

This paper describes fabrication methods used to demonstrate the advantages of nested or Montel optics for micro/nanofocusing of synchrotron X-ray beams. A standard Kirkpatrick-Baez (KB) mirror system uses two separated elliptical mirrors at glancing angles to the X-ray beam and sequentially arranged at 90° to each other to focus X-rays successively in the vertical and horizontal directions. A nested KB mirror system has the two mirrors positioned perpendicular and side-by-side to each other. Compared to a standard KB mirror system, Montel optics can focus a larger divergence and the mirrors can have a shorter focal length. As a result, nested mirrors can be fabricated with improved demagnification factor and ultimately smaller focal spot, than with a standard KB arrangement. The nested system is also more compact with an increased working distance, and is more stable, with reduced complexity of mirror stages. However, although Montel optics is commercially available for laboratory X-ray sources, due to technical difficulties they have not been used to microfocus synchrotron radiation X-rays, where ultra-precise mirror surfaces are essential. The main challenge in adapting nested optics for synchrotron microfocusing is to fabricate mirrors with a precise elliptical surface profile at the very edge where the two mirrors meet and where X-rays scatter. For example, in our application to achieve a sub-micron focus with high efficiency, a surface figure root-mean-square (rms) error on the order of 1 nm is required in the useable area along the X-ray footprint with a ∼0.1 mm-diameter cross section. In this paper we describe promising ways to fabricate precise nested KB mirrors using our profile coating technique and inexpensive flat Si substrates.     

利用调整技术补偿离轴抛物面反射镜面形误差

为了提高光学系统的成像质量,对离轴抛物面反射镜的面形准确度要求越来越高,这大大增加了反射镜的加工难度.本文基于波像差理论,分析了在离轴抛物面反射镜中调整量引入的波像差,提出通过适当调整离轴抛物面反射镜的位置补偿反射镜的面形误差,可以降低离轴反射镜的加工难度、缩短其加工周期、减少加工成本.并借助于ZEMAX软件对一块面形准确度低于λ/40 RMS (λ=632.8 nm)离轴抛物面反射镜进行仿真实验,根据理论计算的调整量调整反射镜的位置,得到了补偿后的离轴抛物面反射镜的面形误差小于λ/60 RMS,仿真结果表明在离轴抛物面反射镜中引入适当的调整量可以有效地补偿反射镜的面形误差.     

同步辐射中双压电片反射镜的研究现状

反射镜是同步辐射光束线中应用广泛的光学元件之一,双压电片反射镜由于具有结构简单、面形能动以及自适应可调等优点,逐渐引起同步辐射界的重视.本文综述了同步辐射中双压电片反射镜的研究现状.主要讨论了双压电片反射镜的工作原理和研究概况,包括在几个大型同步辐射装置中的结构特点、制备技术及面形校正结果等;简要介绍了双压电片反射镜面形校正时所采用的反射波前探测技术和反馈控制算法;最后总结了其发展中存在的关键问题,并展望了其未来的发展方向.     

高功率激光反射镜的几个关键技术

 分析了制作高功率连续激光反射镜材料的热性能、缺陷及其加工工艺, 提出了制作高功率激光反射镜应考虑的几个关键问题: 反射镜材料的综合热性能比值S, 材料的微观结构、缺陷的大小和晶向的选择, 以及加工工艺的设计。并介绍了实验结果。     

Experimente mit dem neutronenspinecho mit langwelligen neutronen aus einem polarisierenden neutronenleiter

We describe an inexpensive method to obtain a highly polarized neutron beam of slow neutrons (λ = 1 – 15 Å) [1]. The high necessary field to saturate the applied soft magnetic material in the surface acting as a polarizing mirror indicates a behaviour of the magnetization in the surface different from that in the bulk material [2]. We also describe the realization of an apparatus proposed by F. Mezei [3], the behaviour of the polarized neutrons in this apparatus, and its use to get a spin echo with a neutron spectrum containing 3 – 9 Å wavelength neutrons. This spin echo is not destroyed by transmission through a nickel sheet, only the number of precessions is increased which appear in a displacement of the echo. This displacement can be used to measure the saturation magnetization of this sheet.     

Study for dual-function EUV multilayer mirror

Studying the distribution of He⁺ in Earth's plasmasphere by detecting its resonantly scattered emission at 304 Å will record the structure and dynamics of the cold plasma in Earth's plasmasphere on a global scale. EUV imaging systems usually utilizes near-normal incidence optics including multilayer mirror and filter. In this paper, the space condition of the Earth's plasmasphere to confirm the expected performance of mirror were analyzed. In order to achieve higher response at 304 Å and reduce 584 Å radiation for the optical system, a new multilayer coating of Mo/Si with UO₂ was developed. Based on optical constants of Mo, Si and UO₂, we used a simplest method to compute the reflectance of this new multilayer mirror range from 100 to 584 Å. The results show the desirable thickness of UO₂ is 17 Å, and the multilayer mirror has a high reflectance of 26.10% at 304 Å and a low reflectance of 0.52% at 584 Å.     

Experimental study of the stability and reflective properties of depleted uranium thin films at a wavelength of 4.5 nm

A technology of depleted uranium thin films, which can be used as high-reflectivity X-ray mirrors at a wavelength of 4.5 nm, is presented. The coefficient of X-ray reflection by these mirrors varies from 90 to 10% at grazing angles between 1° and 10°. The stability of the reflection coefficients for 200-Å-thick depleted uranium films covered by a protective carbon layer 100 and 200 Å in thickness and for 200-Å-thick uranium-nickel films with a nickel content of 9 and 23 wt % is studied. A high-reflectivity mirror is fabricated with the goal of increasing the X-ray radiation intensity in RKK-1-100 X-ray calibration equipment. Advice on fabrication of X-ray mirrors based on depleted uranium films is given.     

Comparison of different types of secondary mirrors for solar application

Two-stage solar concentrators make solar beams downwards providing flexible choices for energy utilization. Five types of secondary mirrors (a flat mirror, an ellipsoidal mirror, a hyperboloidal mirror with upper/lower sheet and a paraboloidal mirror) are compared. Effects of geometry parameters and concentrator precisions on the optical performance are analyzed using Advanced System Analysis Program. The results indicate that concentrators with a flat mirror or hyperboloidal mirror with lower sheet are more sensitive to rim angle or relative location. The secondary mirror is better a convex surface especially when rim angle is more than 90°. A flat mirror or hyperboloidal mirror with lower sheet performs better with higher redirect focal points. A hyperboloidal mirror with upper sheet is the best however numerical aperture changing. The intercept factors decreased with the increase of random errors or optical errors. Both the fabrication and assemblage requirements for a concentrator with a hyperboloidal mirror with lower sheet are the strictest. Experiments are carried out based on a hyperboloidal mirror with upper sheet. The experiments results are in accordance with the ray-tracing results. Therefore, further studies on optimization of the two-stage concentrators using the ray-tracing model can be conducted.     

非球面碳化硅反射镜的加工与检测

为了获得高精度非球面碳化硅(SiC)反射镜,对非球面碳化硅反射镜基底以及改性后碳化硅反射镜表面的加工与检测技术进行了研究。介绍了非球面计算机控制光学表面成型（CCOS）技术及FSGJ-2非球面数控加工设备。采用轮廓检测法和零位补偿干涉检测法分别对碳化硅反射镜研磨和抛光阶段的面形精度进行了检测,并采用零位补偿干涉检测法及表面粗糙度测量仪对最终加工完毕的碳化硅反射镜的面形精度和表面粗糙度进行检测。测量结果表明：各项技术指标均满足设计要求,其中非球面碳化硅(SiC)反射镜实际使用口径内的面形精度（RMS值）为0.016λ(λ=0.6328μm）,表面粗糙度（RMS值）为0.85nm。     

非共轴掠入射KB与KBA X射线显微镜的成像特性分析

由于X射线在介质中被强烈地吸收,加之介质的折射率在X射线波段略小于1,这些因素给X射线成像增加了很多难度,常规的成像方法难以适应X射线波段,目前多采用掠入射反射成像和编码孔径成像方法。详细分析掠入射情况下单镜及双反射镜的成像特性,对组成KBA显微镜的反射镜在掠入射条件下的焦距、视场倾斜、光阑位置等进行研究。研究结果表明：对于双反射镜结构,掠入射角为双反射镜夹角1/2时视场倾斜最少,光阑放在第2个镜子上成像质量优于放在第1个镜子上。最后分析KBA显微镜结构安排的合理性,从而为KBA显微镜设计和加工提供理论依据。     

Fabrication and testing of off-axis parabolic mirrors

Methods have been devised to fabricate and test off-axis segments of parabolic mirrors manufactured from a parent parabolic mirror. Four off-axis parabolic mirrors were fabricated from Zerodur (special grade) by cutting up one large on-axis parabolic mirror. Interferometric measurements were made on the parent mirror and off-axis segments before and after cutting. The measurements show that the surface figure of the segments did not change as a result of the cutting. The surface figure of the final mirror segments was better than λ/13 peak-to-valley and λ/13rms (λ = 0.6328 μm).     

Figure Error Correction by Reflection Wavefront Control of Cu K<Subscript>α</Subscript> Grazing Incidence Multilayer Mirrors

Reflection phase and amplitude of grazing incidence multilayer mirrors for CuK_α radiation have been studied theoretically to evaluate phase correction effects of multilayer surface milling, which revealed good possibilities of correcting mirror substrate figure errors for focusing and imaging application. The mirror multilayers composed of base materials of Cu and Ni were studied in combination with Al, Be, C, Mg and Si for high reflectivity at a grazing angle of 3° incidence. The theoretical surface milling of Cu/Al multilayers of a period thickness of 1.478 nm provides phase correction of 1.7° per period, which corresponds to an accurate correction of substrate figure errors at a rate of 0.007 nm per period. Thus, the milling after the multilayer fabrication, compared to the milling before the multilayer fabrication, enables far more accurate phase correction with 200 times finer control.     

增材制造金属反射镜的发展综述

随着光学测量与遥感领域的不断发展,折反式光学系统对重量、体积和环境适应性等需求不断提高。基于增材制造技术的金属反射镜以其便于实现优化设计、快速制造和加工工艺性好等优点,逐渐获得国内外学者的关注与研究。与传统金属反射镜相比,增材制造金属反射镜可以提高反射镜的结构刚度,同时可实现更高程度的轻量化。增材制造反射镜可以满足光学系统对环境适应性和快速性的需求。本文首先讨论了金属反射镜的评价指标;其次,综述了国内外在基于增材制造技术制备金属反射镜领域的发展现状和技术参数,从增材制造金属反射镜的基体设计与制备和基体的后处理2个方面展开论述;然后,通过分析,总结了增材制造金属反射镜的技术路线和关键技术;最后,对增材制造反射镜的应用前景提出了展望。     

Design and Cold Tests of Asymmetric Quasioptical Resonators

This paper presents the design and test of asymmetric quasioptical resonators for gyrotron applications, where most of the diffraction output coupling comes from the smaller of two mirrors. A computer code based on scalar diffraction theory is used to calculate the resonator losses and the electric field near the mirrors. Resonators with mirror separations approaching confocal have reduced side lobes in the diffraction patterns, which should allow for better power transmission and focusing. Cold tests have been performed at 94 and 141 GHz to measure the quality factor of the asymmetric resonators as a function of mirror separation and mirror misalignment. Typical resonator parameters include 65 cm mirror separation, 1-3% output coupling and 85% of the losses from the small mirror. A half-symmetric resonator with one flat and one curved mirror has also been investigated. The calculated values of Q are in reasonably good agreement with the cold test measurements.     

Walk-Off Ring Coupling Type CO Laser

As a complementary scheme to a coupling-hole type laser, a walk-off ring coupling type laser is proposed to extract a donut shaped beam by shrinking the diameter of one of the stable resonator mirrors. This was successfully applied to a conventional slow axial-flow CO laser. First, finding the intensity distribution close to the Gaussian profile by using a partially transparent mirror in a hemispherical configuration for coupling, we obtain the relationship between the mirror radius and the effective transmittance. Then, using several mirrors with a diameter smaller than the Gaussian profile above instead of the partially transparent mirror, the output power with the donut shape was optimized to yield the maximum power, together with theoretical treatments. This resulted in an optimum mirror diameter of 4.2 mm, which corresponds to the optimum transmittance of 5-6% for the CO laser having the gain parameter G≅0.34, the inherent loss ā ≅ 0.07, and the measure of partial homogeneity m¯ =; 0.5. This value is exactly the same as that of the coupling-hole mirror. Some application feasibilities are also discussed.     

扫描式超高速摄影中转镜镜面变形量的几何补偿

利用三维有限元计算技术,分析了从三面体到八面体铝合金转镜镜面变形规律.发现以四面体为界,三面体转镜镜面变形为向内凹进,五面体及以上转镜镜面则向外凸出.在对镜面变形定量分析基础上,提出了镜面变形的几何补偿方法,即采用柱面代替平直镜面,使镜面变形后的位置趋近于平直.结果表明,对镜面尺寸17.32 mm,轴向长度32.5 mm的三面体铝合金转镜,在5×104 rpm下,镜面最高点偏离平直镜面的最大值为0.468 μm,是平直镜面的1/9,与相同结构尺寸的铍转镜镜面变形量处于相同量级.说明铝合金转镜采用几何补偿方法,可以在扫描式摄影系统中代替铍转镜.     

Design of axisymmetric multi-mirror grazing incidence system to increase the numerical aperture of neutron and X-ray microscopes

An axisymmetric multi-mirror system for neutron and X-ray microscopes is proposed to increase their numerical aperture and collection efficiency. A Wolter type-I mirror is used as the basis of the multi-mirror system at grazing incidence. The addition of an even number of hyperboloid mirrors to the Wolter type-I mirror can satisfy both an equal optical path length and Abbe’s sine condition. The numerical aperture increases in proportion to the number of mirrors. The optical parameters of the system with four tandem mirrors are calculated for neutrons and X-rays with a wavelength of 0.4 nm by assuming that the average grazing angle of incidence is 5.4 mrad and the magnification is 10. The inner diameters of the mirrors are limited to <10 mm considering the total length of the optical system. Tolerance of off-axis distance was calculated using a ray-tracing computer simulation. Ray tracing shows that a blur size <14 nm will be possible at an off-axis displacement of 10 μm.     

折反式超短焦投影镜头设计

针对国内外市场对近距离、大屏幕投影系统中需降低投影镜头加工难度及成本的要求,该文设计了一款超短焦投影镜头。设计过程中选用折反式结构,利用物、像关系原理,结合物方视场计算反射镜面型参数,得出反射镜面型。该方法便于校正大视场畸变、抵消折射镜组的像散和场曲,整个光学系统包括15片球面透镜和一片非球面反射镜,系统总长286 mm,投影距离500 mm,投射画面尺寸254 cm(100英寸),系统投射比0.22,相对照度大于85%,MTF(modulation transfer function)在0.4 lp/mm时大于0.5,水平TV畸变小于0.55%,垂直TV畸变小于0.65%。该系统的多项设计指标均优于市面上现有的产品指标,采用同轴球面设计易于加工、装调,可有效降低生产成本。     

Study of tin amalgam mirrors by 119Sn Mössbauer spectroscopy and other analytical methods

From the beginning of the 16 ^th until the end of the 19 ^th century the most widely used mirrors consisted of a pane of glass backed with a reflecting layer of tin-mercury amalgam. They were made by sliding the glass pane over a tin foil covered with liquid mercury. After removal of the superfluous mercury, tin amalgam formed slowly at ambient temperature and yielded a reflecting layer adhering to the surface of the glass. Such mirrors often deteriorate in the course of time by oxidation of the tin in the amalgam to stannous or stannic oxide. ¹¹⁹Sn Mössbauer spectroscopy, scanning electron microscopy, micro-XRF and X-ray diffraction have been used to study this deterioration process. The studied specimens were a modern mirror made for the reconstruction of the Green Vault in Dresden in the early 2000s, two rather well preserved German mirrors from the 17 ^th and 19 ^th centuries and several strongly deteriorated specimens of Baroque mirrors from the south of Spain. The modern mirror consists mainly of a Sn_0.9Hg_0.1 amalgam with only 2 % of SnO₂. The older German mirrors showed more pronounced oxidation, containing 12 and 15 % of SnO₂, which did not noticeably impair their reflectivity. In the samples from the Spanish mirrors at best a few percent of metallic phase was left. The majority of the tin had oxidised to SnO₂, but between 8 and 20 % of the tin was present as SnO. X-ray diffraction yielded similar results and micro-XRF mapping using synchrotron radiation for excitation gave information on the distribution of Sn and Hg in the reflecting layer of the mirrors.     

Back-side-coated chirped mirrors with ultra-smooth broadband dispersion characteristics

We demonstrate a new technique for the design of chirped mirrors with extremely smooth dispersion characteristics over an extended ultra-broadband wavelength range. Our approach suppresses spectral dispersion oscillations, which can lead to unwanted strong spectral modulations and limit the bandwidth of mode-locked laser pulses. Dispersion oscillations are significantly reduced by coating the chirped mirror structure on the back side of a substrate, providing ideal impedance matching between coating and ambient medium. An anti-reflection coating may be added on the front side of the substrate, geometrically separated from the chirped mirror. The chirped mirror structure and the anti-reflection coating are non-interfering and can be independently designed and optimized. The separation of both coating sections provides a much better solution for the impedance-matching problems than previous approaches to chirped mirror design. We show by a theoretical analysis and numerical simulations that minimum dispersion oscillations are achieved if the index of the substrate is identical to the index of one of the coating materials and if double-chirping is used for the chirped mirror structure. Based on this analysis, we design a mirror that supports a bandwidth of 220 THz with group delay dispersion oscillations of about 2 fs² (rms), an order-of magnitude improvement compared to previous designs of similar bandwidth. In a first experimental demonstration of back-side-coated (BASIC) mirrors, we achieve nearly transform-limited and virtually unchirped pulses of 5.8 fs duration from a Kerr-lens mode-locked Ti:sapphire laser. BASIC mirrors are particularly suited for higher-order dispersion compensation schemes. They support the extremely broad spectra of few-cycle pulses and promise to provide clean pulse shapes in this regime. Received: 19 April 2000 / Published online: 6 September 2000