月基极紫外相机多层膜反射镜

月基极紫外相机用于月球表面对地球等离子体层辐射出的30.4 nm谱线进行成像观测,多层膜反射镜是月基极紫外相机的重要光学元件。根据月基极紫外相机技术参数,选择了B₄C/Mg,B₄C/Mg₂Si,B₄C/Al,B₄C/Si,Mo/Si等材料,对其周期厚度、材料比例、周期数等参数进行优化。计算了以上材料组合在30.4 nm的反射率曲线。考虑到月球环境的特殊性和材料的物理化学性质,从中选择出Mo/Si和B₄C/Si两种组合,利用磁控溅射进行镀制。Mo/Si和B₄C/Si多层膜在30.4 nm反射率分别达到15.3%和22.8%。     

极紫外多层膜技术研究进展

在极紫外波段,任何材料都表现出极强的吸收特性,因此,采用多层膜实现高反射率是构建正入射式光学系统的唯一途径。本文总结了极紫外多层膜的发展进程,叙述了制备极紫外多层膜的关键技术(磁控溅射、电子束蒸发、离子束溅射)以及它们涉及的相关设备。由于多层膜反射式光学元件主要应用于极紫外光刻与极紫外天文观测,文中重点讨论了极紫外光刻系统对多层膜性能的要求,镀膜过程中的面形精度和热稳定性等问题;同时介绍了极紫外天文观测中使用的多层膜的特点,特别讨论了多层膜光栅的制备技术和亟待解决的问题。     

软X光多层镜反射率在同步辐射源上的标定

 软X光多层镜反射率标定实验在北京同步辐射装置 上进行,利用BSRF-3W1B 束线及其反射率计靶室(主靶室)标定不同材料的多层镜样品的反射率。多层镜的标定采用波长扫描法,以得到样品反射率随波长变化的曲线。给出了21°-B₄C/Si,21°-B₄C/Mo,10°-Cr/Ti,15°- B₄C/W,10°- B₄C/W以及6.86°-B₄C/W等6块多层镜在50～1 500 eV能段上的反射率标定曲线,并将其与理论计算结果进行比较。结果表明：标定曲线与理论曲线很好地符合。影响标定结果的总不确定度的主要因素是光子能量不确定度,其次是角度不确定度,测量不确定度的影响很小。     

q软X光多层镜反射率在同步辐射源上的标定

软X光多层镜反射率标定实验在北京同步辐射装置上进行,利用BSRF-3W1B 束线及其反射率计靶室(主靶室)标定不同材料的多层镜样品的反射率.多层镜的标定采用波长扫描法,以得到样品反射率随波长变化的曲线.给出了21°-B4C/Si,21°-B4C/Mo,10°-Cr/Ti,15°- B4C/W,10°- B4C/W以及6.86°-B4C/W等6块多层镜在50～1 500 eV能段上的反射率标定曲线,并将其与理论计算结果进行比较.结果表明标定曲线与理论曲线很好地符合.影响标定结果的总不确定度的主要因素是光子能量不确定度,其次是角度不确定度,测量不确定度的影响很小.     

Spectral characterization of EUV radiation emitted from a laser-irradiated gas puff target

A laser-plasma EUV source is described, which is going to be utilized for characterization of EUV optical components and sensoric devices in the wavelength region from 11 to 13 nm. EUV radiation is generated by focusing a Nd:YAG laser into a double stream gas puff target. By the use of different target gases, broadband as well as narrow-band EUV radiation can be obtained. The emission characteristics of the radiation is monitored by the help of different diagnostic tools including a pinhole camera, an EUV spectrometer, and various EUV photodiodes, either directly or after reflection from multilayer mirrors. Theoretical calculations of collision-induced energy transfer are given in order to explain the observed high degree of electronic excitation in the utilized target gases.     

19.5nm极紫外反射镜的研制

介绍了一种用于太阳观测19.5nm极紫外多层膜的研究工作。利用软件对规整的Mo/Si膜系结构进行了优化,拓宽了反射带宽,提高了积分反射率。采用双离子束溅射技术,时间控厚,成功制备了该反射镜。通过同步辐射反射率计测试表明,峰值反射率27.5%,均匀性在1%以内,已初步达到预设要求。     

Identifying contributions of individual layers constituting multilayer dielectric mirrors

First-order approximations have been used to study the recursion expressions of the reflection and transmission coefficients of a weakly absorptive multilayer mirror. It has been proved that in the proximity of the central frequency ω₀ of a quarter-wave mirror, contributions of an individual layer to the reflection delay time and absorption-induced reflectivity reduction can be quantitatively specified with a single weighting factor pertinent to that layer. Derivations have indicated that the absorption-induced reductions of mirror reflectivity and reflection delay can be reduced by selecting an odd layer number and a large index ratio between alternating high and low refractive index coating materials. Calculations have also suggested that the absorbed incident light is not distributed, among the reflected and transmitting parts, according to the ratio between the reflectivity and potential transmission.     

CO2 laser assisted removal of UO2 and ThO2 particulates from metal surface

Pulsed laser assisted removal of uranium dioxide and thorium dioxide particulates from stainless steel surface have been studied using a TEA CO₂ laser. Decontamination efficiency is measured as a function of laser fluence and number of pulses. Threshold fluence for the removal of UO₂ particulates has been found to be lower than that required for the removal ThO₂ particulates. Usage of a ZnSe substrate, that is transparent to the laser wavelength used here, enabled us to decouple the cleaning effect arising out of absorption in the particulates from that in the substrate and has contributed towards understanding the mechanism responsible for cleaning. The experimental observations are also corroborated by simple theoretical calculations.     

On the Use of Depleted Uranium Dioxide as a Neutron Filter

A simple additive formula is given which, for neutron energies in the range 10^-4 < E<10 eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections of a crystalline material as a function of its crystal constants and temperature. Computer codes PUO and SUO were developed to calculate the total attenuation of reactor neutrons through poly- and mono-crystalline samples, respectively. The codes were applied to calculate the total cross-section of polycrystalline uranium and thorium dioxides in the energy range from 4 meV to 1 eV. The obtained agreement between the calculated values and available experimental values justifies the applicability of the used formula and the computer codes. A feasibility study on using depleted polycrystalline uranium dioxide as a cold neutron filter and the single crystal as a thermal neutron filter is given. The optimum crystal parameters and thickness for efficiently transmitting the thermal reactor neutrons while strongly attenuating both fast neutrons and -rays accompanying the thermal ones is also given.     

Two channel multilayer mirrors for astrophysics

A two-channel mirror reflecting both Fe-IX/X (λ = 17.1 nm) and He-II (30.4 nm) resonance lines at near normal incidence has been designed, fabricated and characterized. These two passbands are often chosen in space instruments designed for the observation of the solar corona. The mirror structure used for optimization is a superposition of two periodic multilayers with three components per period. It has been designed by using optimization software with an appropriate merit function. The theoretical reflectivity for both resonance lines can reach 0.25. It is shown that, by using a set of filters, one can select either the Fe-IX/X or the He-II channel. The spectral response of the two-channel mirror has been measured on synchrotron radiation source on a large wavelength range, from 12 nm to 35 nm. Experimental reflectivity reaches 0.32 for the Fe-IX/X line and 0.19 for the He-II line.     

中心波长为28.5nm多层膜镜反射率测量

在“星光-Ⅱ”装置上以类Ne铬x射线激光作为标定源，以平场光栅谱仪为分光元件进行了285nm的Mo/Si多层膜反射镜效率测量.介绍了实验方法，给出了实验结果，本次研制的两块多层膜镜反射率分别为31%和9.6%. 关键词： x射线多层膜反射镜 反射率测量 x射线激光     

二己二硫醚多层膜局域结构的近边x射线吸收精细结构研究

利用多重散射团簇(MSC)方法计算了二己二硫醚［CH₃(CH₂)₅S］₂单分子和多分子硫原子近边x射线吸收精细结构(NEXAFS)谱，给出了二己二硫醚多层膜的局域结构模型. MSC研究显示多层膜中二己二硫醚分子作平行有序排列，彼此相距0.47nm，其横截面呈规则的正方形. 利用离散变分Xα方法计算了二己二硫醚单分子和多分子的电子结构，验证了MSC的计算结果；并阐明了NEXAFS谱中各峰的物理起源. 对多层膜中分子之间的相互作用进行了讨论，发现多层膜的局域结构有分子自组装的特性. 关键词： 3(CH₂)₅S］₂多层膜')" href="#">二己二硫醚［CH₃(CH₂)₅S］₂多层膜 近边x射线吸收精细结构 多重散射团簇方法 离散变分Xα方法     

Model multilayer structures for three-dimensional cell imaging

The prospects for SIMS three-dimensional analysis of biological materials were explored using model multilayer structures. The samples were analyzed in a ToF-SIMS spectrometer equipped with a 20 keV buckminsterfullerene (C₆₀⁺) ion source. Molecular depth information was acquired using a C₆₀⁺ ion beam to etch through the multilayer structures at specified time intervals. Subsequent to each individual erosion cycle, static SIMS spectra were recorded using a pulsed C₆₀⁺ ion probe. Molecular intensities in sequential mass spectra were monitored as a function of primary ion fluence. The resulting depth information was used to characterize C₆₀⁺ bombardment of biological materials. Specifically, molecular depth profile studies involving dehydrated dipalmitoyl-phosphatidylcholine (DPPC) organic films indicate that cell membrane lipid materials do not experience significant chemical damage when bombarded with C₆₀⁺ ion fluences greater than 10¹⁵ ions/cm². Moreover, depth profile analyses of DPPC-sucrose frozen multilayer structures suggest that biomolecule information can be uncovered after the C₆₀⁺ sputter removal of a 20 nm overlayer with no appreciable loss of underlying molecular signal. The experimental results support the potential for three-dimensional molecular mapping of biological materials using cluster SIMS.     

摆臂式三点光学镜面支撑系统的研究

提出了一种摆臂式三点光学镜面支撑系统,分析了其结构原理和工作性能,给出了实现的方法和制造工艺。该支撑系统具有结构简单、刚度恒定以及无附加温度应力等特点,可用于中小型光学镜面和光学元件的支撑,特别适用于空间仪器的光学加工领域。     

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.     

Microstructure and tribological properties of WS2/MoS2 multilayer films

In this paper, a novel method, namely, magnetron sputtering and low temperature ion sulfurizing combined technique was used to fabricate the solid lubrication WS₂/MoS₂ multilayer films. Scanning Electron Microscopy (SEM) was used to observe the surface and worn scar morphologies. X-ray diffraction (XRD) was utilized to analyze the phase structure. The nano-hardness and elastic modulus of WS₂/MoS₂ multilayer films were surveyed by the nano-indentation tester. The friction and wear test were conducted on a ball-on-disk wear tester under dry sliding condition. The results obtained showed that the WS₂/MoS₂ multilayer films exhibited a lower friction coefficient and better wear-resistance when compared with single WS₂ film and original 1045 steel.     

Magnetic properties and static-dynamic magnetostrictive characteristics for SmFe2/Fe exchange-coupled multilayers

Giant magnetostrictive SmFe₂/Fe exchange-coupled multilayers were fabricated by ion beam sputtering deposition on glass substrates. The effects of SmFe₂/Fe exchange coupling action and vacuum annealing on soft-magnetic property and static-dynamic magnetostrictive characteristics of SmFe₂/Fe multilayers were investigated. The results showed that the soft-magnetic, static-dynamic magnetostrictive characteristics were greatly improved by SmFe₂/Fe exchange coupling action and proper vacuum annealing treatment temperature. Compared with that of SmFe₂ single film, the coercivity in the direction of easy magnetization axis for SmFe₂/Fe exchange-coupled multilayers exhibited a greater decrease. Better soft-magnetic properties were achieved (H_c=2.54 kA/m, M_s=120.38 emu/g, and M_r/M_s=0.21) after vacuum annealing at certain temperature. The magnetostrictive coefficient for SmFe₂/Fe exchange-coupled multilayers was about 135 ppm at 16 kA/m magnetic field. At first order resonant frequency (99.2 Hz), the amplitude peak-peak value for the as-deposited SmFe₂/Fe exchange-coupled multilayers was 46 μm. After the vacuum annealing treatment at 250 °C, the amplitude peak-peak value increased to 650 μm.     

Design and performance of two-channel EUV multilayer mirrors with enhanced spectral selectivity

In this paper, we present a study on two-channel multilayer mirrors which can operate at two wavelengths in Extreme Ultraviolet (EUV) spectral range. We propose a new method to design two-channel EUV multilayer mirrors with enhanced spectral selectivity. The mirror structure is a stack of two periodic multilayers separated by a buffer layer. We have defined the main parameters which allow adjustment of the distance between different order Bragg’s peak and of wavelength positions of reflectivity minima. Two mirrors have been designed and deposited for solar EUV telescope applications by using this method. The first mirror reflects Fe IX–X line (17.1 nm) and Fe XVI (33.5 nm) lines with attenuation of the He II line (30.4 nm). The second mirror reflects Fe IX–X and He II lines with attenuation of Fe XV (28.4 nm) and Fe XVI lines. Measurements with synchrotron radiation source confirm that, in both cases, for these mirrors, we are able to adjust reflectivity maxima (Bragg peak position) and minima. Such multilayers offer new possibilities for compact design of multi-wavelength EUV telescopes and/or for high spectral selectivity.     

Preparation of sol-gel ZrO2-SiO2 highly reflective multilayer films and laser-induced damage threshold characteristic

Sol-gel (ZrO₂/SiO₂)¹² ZrO₂ films were prepared by spin coating method. The reflectivity spectrum of the films was measured with a Lambda 900 spectrometer. In order to investigate laser-induced damage threshold (LIDT) characteristic of highly reflective films, one-layer ZrO₂ and SiO₂ films, two-layer ZrO₂/SiO₂ and SiO₂/ZrO₂ films were also prepared by spin coating method. LIDT of each film was measured. Damage morphology after laser irradiation was characterized by optical microscopy (Nikon E600K). The experimental results showed that the reflectivity of (ZrO₂/SiO₂)¹² ZrO₂ film at 1064 nm and 355 nm wavelength is 99.7%. The LIDT results decreases as the number of layer of films increases. All the films have similar damage morphology. The experimental results are explained by the different temperature profiles of the films.     

Periodic adjustment of the position of a laser beam spot on a semiconductor saturable absorber mirror in a passively mode-locked solid-state laser

A laser diode end-pumped passively mode-locked Nd:YVO₄ solid-state laser with a semiconductor saturable absorber mirror (SESAM), in which the intracavity laser beam spot on the SESAM can be adjusted periodically, is investigated. Inserting a rectangular prism (RP) into the laser cavity is a promising approach towards the goal of periodically moving the position of the focus spot of the intracavity pulse on the SESAM surface to avoid the long-time irradiation of the laser beam on the same position, thereby solving a series of problems caused by damage to the SESAM and greatly prolonging its usage life. The adjustment of the rectangular prism in the laser cavity does not break the stable continuous wave (CW) mode-locked condition. The laser generates a stable picosecond pulse sequence at 1064 nm with an output power of 3.6 W and a pulse width of 14 ps. The instabilities of the output power and the pulse width are 1.77% and 4.5%, respectively.