中性束注入器真空系统差分抽气性能优化研究北大核心CSCD

中性束在真空室内传输的过程中需要一个真空梯度分布的环境,EAST中性束注入器(NBI)的真空室采用差分式结构来满足真空梯度分布的要求。真空室内气体挡板安装位置的不同会影响真空空间气体分子密度分布,从而对真空梯度的分布产生影响。运用Molflow软件模拟分析气体挡板在不同安装位置情况下,真空室内真空梯度和后低温冷凝屏热负荷分布的分布情况,分析得出了L=1.35~1.38 m是气体挡板最佳的安装位置。为CFETR NBI真空室的真空梯度的设计提供一定的借鉴和参考。     

中性束注入器真空系统差分抽气性能优化研究

中性束在真空室内传输的过程中需要一个真空梯度分布的环境,EAST中性束注入器(NBI)的真空室采用差分式结构来满足真空梯度分布的要求。真空室内气体挡板安装位置的不同会影响真空空间气体分子密度分布,从而对真空梯度的分布产生影响。运用Molflow软件模拟分析气体挡板在不同安装位置情况下,真空室内真空梯度和后低温冷凝屏热负荷分布的分布情况,分析得出了L=1.35～1.38 m是气体挡板最佳的安装位置。为CFETR NBI真空室的真空梯度的设计提供一定的借鉴和参考。     

细水雾对障碍物挡板火灭火有效性的实验研究

在不同障碍物挡板阻隔条件下，就细水雾对油池火的灭火效果进行了实验研究，分析了不同空间位置的障碍物挡板对细水雾灭火效果的影响，采用FDS40对细水雾与不同类型障碍物挡板油池火的相互作用过程的模拟结果表明：障碍物结构与类型影响着细水雾直接作用于油池火上方的水雾通量，油池火上方的水雾卷吸量越大，细水雾对障碍火的灭火效果越明显。     

追踪算法在纳米晶粒薄膜散射研究中的应用

本文通过光线追踪算法结合基于麦克斯韦方程解的蒙特卡洛方法,模拟了光在梯度折射率指数硅/非晶硅(C-Si/a-Si)复合薄膜中的传播情况.文中将梯度折射率指数薄膜考虑成多层均匀折射率薄膜的叠加,每一层的折射率由该层所在位置决定.通过对透射、反射光子在梯度折射率指数薄膜中运动的统计研究,讨论梯度折射率指数薄膜的减反射性能.模拟结果获得了薄膜中粒子的浓度、粒子直径大小以及折射率梯度变化对薄膜反射率的影响规律,这有助于低反射率薄膜的设计,以期解决目前较为引人关注的镀膜玻璃光污染问题.     

椭球反射镜膜厚均匀性

本文分析了椭球反射镜膜层厚度均匀性对反射率的影响,从理论上得到膜厚计算公式。根据计算的膜厚分布设计了遮蔽板,获得较好的反射特性。     

C/C复合材料的旋转偏振成像方法

本研究提出了一种旋转偏振显微成像方法。根据热解碳独特的双反射特性,设计了仅有一个检偏镜的显微图像采集系统;通过检偏镜的旋转,获取C/C复合材料在不同偏振角位置的单偏光图像;经过图像配准和图像融合,合成最大、最小反射率和双反射率映射图像。这种映射图像反映的信息是采用常规显微镜法不能观察到的,它直观地揭示了材料内部的微观结构特征,可以作为测定热解碳真实反射率的基础。本研究可为C/C复合材料微观结构分析以及相关特征参数测量提供理论依据和实现途径。     

多联机室外机百叶隔栅优化

通过数值模拟的方法对上海市某建筑物多联机室外机机房风百叶进行了设计优化,具体分析了来流速度、百叶挡板倾斜角度、百叶挡板宽度与百叶挡板垂直间距的比值及百叶挡板宽度、厚度对风口阻力系数的影响,并研究了其在自然风速下该百叶的挡雨性能。     

非均匀SiO2-H2O纳米流体辐射特性研究

建立具有梯度折射率的SiO_2-H_2O纳米流体辐射传递模型,利用间断有限元法求解其在持续脉冲辐射下的透射率、反射率。通过与均匀纳米流体的透射率、反射率进行对比,分析非均匀纳米流体对辐射吸收效果的影响。同时考虑非均匀条件下折射率梯度、SiO_2质量分数以及颗粒粒径对纳米流体的反射率及透射率的影响。结果表明:当纳米流体具有梯度折射率时,反射率及透射率均减小,吸收率从30%提高到了41. 9%;而折射率梯度的增大使得反射率及透射率进一步减小; SiO_2质量分数和颗粒粒径的增大则导致反射率增大,透射率减小。     

内置有水平挡板的矩形储液器非线性晃动分析

该文以内置有水平挡板的矩形储液器为研究对象,对储液器的非线性晃动问题展开研究。利用势流理论和虚功原理,推导了由水平挡板引起的储液器非线性阻尼比(非线性体现于波高有关)的计算公式,同时考虑水平挡板对储液器晃动频率的影响而对非线性阻尼比计算公式进行了修正。结合液体晃动的非线性分析理论,研究了水平挡板处于不同位置、挡板长度不同时储液器的液面波高与晃动力变化情况。利用Fluent软件进行了数值模拟,并与理论模型分析的结果进行对比。结果表明：当水平挡板靠近储液器底部或长度较小时,储液器内液体的非线性晃动现象较明显,利用非线性三阶模态方程推导得到的波高、晃动力与数值模拟结果较接近,而仅考虑一阶线性响应会明显低估储液器液面波高,但其求解的晃动力却与考虑非线性值的状况基本一致;随着挡板到自由液面距离的变小或挡板长度的增大,储液器液面波高、晃动力幅值减小,液体晃动呈线性变化,说明水平挡板靠近自由液面或增大其长度时能够提高储液器的阻尼比,进而也更能抑制液体的非线性晃动。同时水平挡板逐渐靠近自由液面或长度逐渐增大时,储液器晃动频率逐渐减小,减小的幅度分别可达到5.7%～28%。     

带挡板的转筒混料器的离散颗粒模拟

用离散颗粒模拟方法计算了带两块挡板的旋转混料器中所有颗粒的三维运动。该模拟法可用于单组分球形颗粒的混合。本文研究了挡板对颗粒运动和颗粒混合的影响，研究表明，表示混合程度与时间之间关系的混合曲线在数值上与过去实验结果很吻合。同该模拟法可以预言：对于颗粒混合，挡板有一个最佳长／高比，且料层的变形也受其影响。带挡板的转筒混料器的离散颗粒模拟@YoshitsuguMuguruma     

High-performance Mo-Si multilayer coatings for extreme-ultraviolet lithography by ion-beam deposition

An ion-beam deposition system has been used to fabricate Mo-Si multilayer coatings for masks and imaging optics to be used for extreme-ultraviolet lithography. In addition to high reflectivity and excellent profile control, ion-beam deposition has the capability to smooth rough substrates. For example, we achieved reflectivity of 66.8% on a substrate with 0.39-nm roughness. Smoothing can be further enhanced with a second ion source directed at the multilayer coating. The smoothing capabilities relax the requirement on the finish of the mirror and the mask substrates and could dramatically reduce the cost of these components. Thickness profile control is in the +/-0.01% range, and the figure error added to the mirror substrate by errors in the multilayer thickness is less than 0.1 nm. Peak reflectivities obtained on smooth substrates are 67.5-68.6%.     

Apodizing holographic gratings for the modal control of semiconductor lasers

We first present the fabrication technique of apodizing holographic gratings. Gratings with a spatially variable reflectivity profile were obtained by the interference of two Gaussian beams on a glass plate covered with a photoresist. When the exposure time was short enough to avoid saturation of the photoresist, gratings with a quasi-Gaussian reflectivity profile for the beam reflected in the -1 order were produced; the reflectivity at the center could be as high as 71%, and the half-width of the reflectivity profile at the e(-1) position could be as small as 180 mum. Apodizing gratings were used as the end mirror of the external cavity of a broad-area semiconductor laser. Single longitudinal- and lateral-mode operation was observed over the full range of allowed injection currents.     

Performance of high-density cast silicon carbide in the extreme ultraviolet

The normal-incidence reflectance of high-density cast silicon carbide (SiC) is evaluated in the extreme ultraviolet (EUV) spectral region. High reflectivity in the EUV is achieved. High reflectivity and the relatively low-cost manufacturing process make high-density cast SiC a promising mirror material for EUV applications.     

Optical performance of extreme ultraviolet lithography mask with an indium tin oxide absorber

In this study, we propose a new extreme ultraviolet (EUV) binary mask with an indium tin oxide (ITO) absorber. The optical constant of ITO film at 13.5 nm wavelength in the EUV regime was determined by means of X-ray reflectivity measurements and the chemical composition was determined using Rutherford backscattering spectrometry. The reflectance of a binary mask with an ITO absorber layer at various thicknesses was also measured to investigate the optical performance in the EUV regime. It was found that the extinction coefficient of ITO film is higher than that of a typical absorber layer, TaN, and that the reflectance of the ITO absorber in the binary mask at a wavelength of 13.5 nm is reduced to 0.62% at a thickness of 45 nm. Therefore, it is expected that the ITO film can be employed as a thin absorber of a binary mask to reduce the geometrical shadow effect in extreme ultraviolet lithography.     

Wolter type I x-ray focusing mirror using multilayer coatings

A multilayer coating is a useful addition to a mirror in the x-ray region and has been applied to normal incidence mirrors used with soft x rays. When a multilayer coating is used on grazing incidence optics, higher performance can be achieved than without it. Cr/Sc multilayers coated on a Wolter type I mirror substrate for a soft x-ray microscope are considered. The reflectivity and effective solid angle are calculated for Wolter type I mirrors with uniform and laterally graded multilayer coatings. The laterally graded multilayer mirror showed superior x-ray performance, and the multilayer tolerances were relaxed. This multilayer mirror could be especially useful in the soft x-ray microscope intended for biological applications.     

具有渐变层半导体DBR的MOCVD外延制备

应用金属有机化合物气相淀积(MOCVD)制备了具有渐变层的半导体布拉格反射镜(DBR),分别是抛物线性、线性和突变结构的DBR.三种反射镜结构都设计为8个周期,通过白光反射谱测量突变DBR具有最大反射率.应用原子力显微镜对所制备的DBR表面形貌进行分析.结果表明,相同周期数情况下线性渐变DBR相对于其他两种结构粗糙度最小,具有良好的表面形貌,可以应用于垂直腔面发射激光器的研制.     

Graded reflectivity micromirror arrays

A technique for fabricating arrays of graded reflectivity micromirrors with diameters as small as 25 microm is reported. It is based on laser-induced physical vapor deposition through microholes on a thin free-standing noncontact mask, and it is suitable for applications in micro-optics and solid-state laser technology.     

Generation of flattened Gaussian beam profiles in a Nd:YAG laser with a Gaussian mirror resonator

We report the experimental generation of a family of flattened Gaussian beams with bell-shaped, flattened, and annular intensity profiles in an electro-optically Q-switched Nd:YAG laser with a variable reflectivity mirror of a Gaussian reflectivity profile as an output coupler. The laser beams of different profiles were generated by modifying the resonator magnification. The propagation characteristics of the experimentally generated flat Gaussian beams were found to be in agreement with theory. To the best of our knowledge this is the first time such a family of flattened Gaussian beams is experimentally generated intracavity using a single variable reflectivity mirror.     

Kollektorbeschichtungen für die EUV‐Lithografie

Collector Coatings for EUV Lithography Extreme ultraviolet lithography (EUVL) is the next generation lithogra phy method operating at the wavelength of 13.5 nm (14 times shorter than current lithography systems), enabling semiconductor scaling to resolutions of 22 nm and below [1]. This paper presents the successful coating of the world's largest ellipsoidal collector mirror for EUV radiation with a diameter of 660 mm ( Fig. 1 ). In order to achieve the required peak reflectivity of more than 65 %, the ellipsoidal collector was coated with a highly reflective, laterally graded multilayer using the dc magnetron sputtering system “NESSY”. A maximum reflectivity of the laterally graded multilayer of more than 65 % was achieved for radii smaller than 220 mm. For radii between 230 mm and 320 mm the reflectivity decreases to a minimum of 58 %. The targeted wavelength remains constant at (13.50 ± 0.05) nm over the entire collector surface which is well within the tight specifications for high volume manufacturing.     

Reflectance of a wideband multilayer x-ray mirror at normal and grazing incidences

The reflectance of a W-B(4)C multilayer mirror, with a period thickness that increased with depth into the multilayer, was measured at near-normal incidence with synchrotron radiation and at grazing incidence with Cu Kα radiation. The period thickness increased linearly from 17.9 ? at the top of the multilayer structure to 21.9 ? at the substrate while the same ratio of nodal layer to period thickness was maintained. For a grazing angle of 80° (10° from normal incidence), the peak reflectance was 1.1% at a wavelength of 36 ?, and the reflectance profile was 1 ? wide. For Cu Kα radiation the reflectance peaked at a grazing angle of 2.4° and was 0.4° wide. Compared with a W-B(4)C multilayer mirror with a constant period thickness, the depth-graded multilayer mirror has wider reflectance profiles at near-normal and grazing incidences, resulting in larger integrated reflectances and wider fields of view.