扫描电子显微镜成像信号分析

介绍了扫描电子显微镜（SEM）的基本工作原理,着重分析了在SEM初始电子束作用下,各种成像信号产生的方式及其特点,确定二次电子信号因成像分辨率高、携带成像信息丰富而成为SEM的最终信号源。针对此信号在实际应用中暴露出的缺陷,介绍了解决办法,从而使SEM的成像性能得以大幅提高,使用范围大为扩展。     

Liquid pool helium cryopump

A liquid pool helium cryopump, without liquid nitrogen bath, is described. The details of its construction and experimental results are presented.     

Calibrating a scanning electron microscope in two coordinates by the use of one certified dimension

A method is proposed for calibrating a scanning electron microscope that corresponds completely to national standards providing unification of measurements in nanotechnology. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 18–20, June, 2008.     

液氢温区冷氦增压系统试验研究

针对某型号火箭冷氦增压系统,建设了液氢温区冷氦增压系统试验平台,通过试验得到了冷氦气源压力和温度、冷氦加热器性能、模拟贮箱压力和温度的变化规律.结果表明:低温制冷机组配合高压低温换热贮罐可以真实模拟箭上的冷氦气源;根据对增压过程中贮箱压力的分析表明排气方式可以真实模拟箭上推进剂消耗过程中贮箱压力的变化情况;另外,试验中压力信号器、电磁阀和贮箱工作正常,验证了火箭冷氦增压系统的可靠性.     

A test object with three certified linewidth dimensions for a scanning electron microscope

A test object for a scanning electron microscope, which has a trapezoidal profile of the relief with large angles of inclination of the side walls, is developed. The test object contains elements (protrusions) with three certified dimensions of the linewidth, situated in two mutually perpendicular directions. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 49–52, September, 2008.     

周期性冲击对大型超导核聚变低温系统氦透平膨胀机影响研究

超导核聚变装置磁体会因"交流损耗"而产生大量的热,迫使磁体内通道压力升高,导致与之直接相连的氦透平膨胀机的运行稳定性与运行效率受到严重影响,从而影响超导核聚变实验。详细分析超导核聚变装置用低温氦透平膨胀机受周期性冲击的机理与不可回避性,并用提高氦透平膨胀机本身性能、改善制动调节与氦透平膨胀机出口压力调节的反馈控制思想,得出一些提高氦透平膨胀机稳定性、降低冲击的方法。高效气体轴承与优化的转子结构可以有效提高氦透平膨胀机本身的抗干扰能力;快速响应制动功率,使之与负载匹配,可有效改善外界干扰程度;氦透平膨胀机出口压力快速调节,可降低氦透平膨胀机进出口参数,降低影响。     

Evaluation of annular pupil for scanning transmission electron microscope formed by focused ion beam technique

Annular pupils for electron optics were developed using a focused ion beam (FIB) technique to realize an increase in the depth of focus, aberration-free imaging and separation of amplitude and phase images under scanning transmission electron microscopy (STEM). A tantalum plate 30 μm thick was used as the annular pupil material in the present experiment. The annular pupils were designed with various outer diameters from ?120 μm to ?40 μm. The inner diameter was designed at 60 to 80% of the outer diameter. The fabricated annular pupils were inspected by scanning ion beam microscopy and scanning electron microscopy. Annular pupils were successfully obtained at the designed size, although the slits of the pupils were slightly tapered by the ion beam etching process. These annular pupils were loaded on a STEM and confirmed to display no charge-up phenomenon by observation of the projection image on a scintillator using a CCD camera. We confirmed the image taken by annular pupil with narrow width was able to suppress the influence of the normal illumination.     

Liquid-helium stage in a scanning electron microscope

A liquid-helium stage to be inserted into a scanning electron microscope (SEM) is described. The sample chamber, which is filled with liquid helium, has a volume of about 8 × 7 × 5 cm³. Translation of the cooled sample in x, y, and z directions is possible during electron-optical observation. Since mounting the liquid-helium stage to the SEM can be performed in less than 30 min, switching the SEM from regular operation at room temperature to the low-temperature mode and back is relatively easy. After cooling the system to 4.2 K, a 3 litre helium reservoir allows experimentation near 4.2 K for about 5 h.     

EAST低温系统俄制氦透平膨胀机维修改进与测试

EAST氦低温系统是EAST( Experimental Advanced Super-conducting Tokamak)先进超导托卡马克实验装置重要子系统之一,4台不同进口参数的氦透平膨胀机又是EAST氦低温系统的核心部件,4种类型的氦透平膨胀机全是俄罗斯进口的氦透平膨胀机,其启动过程稳定差,易损坏.主要对俄制损...     

Liquid helium cryostat for target cooling

A liquid helium cryostat for target cooling down to temperature 1.3 K has been developed. The essential technical details and experimental results are presented. A moving target holder is proposed.     

环境扫描电子显微镜的成像特点

环境扫描电子显微镜(ESEM)中所指的环境并非真正意义上的大气环境(760 Torr),与传统扫描电子显微镜(SEM)样品室高真空度相比,ESEM样品室的真空度可以很低(约达20 Torr)。ESEM是在传统的SEM样品室中多一个GSED探头,因此,它在传统的SEM基础上增添了新的功能。其主要的特点是,可以观察含适量水分的样品和非导体材料样品,比如植物的叶片、动物中的昆虫、作物的籽粒、含结晶水的固体材料等。     

低温氦气体轴承透平膨胀机实验系统设计

设计了一套氦透平膨胀机实验系统,该系统可以用来对工作在液氢—常温区范围内的不同规格的氦透平膨胀机进行性能测试,还可以用于开展以氦为工质的低温环境下透平膨胀机实验研究,以期掌握氦透平膨胀机的关键技术并进一步提高氦透平膨胀机的性能。     

Analysis of activated slip systems in fatigue nickel polycrystals using the EBSD-technique in the scanning electron microscope

By comparison of the observed trace angles of active slip planes with the expected traces in plastically deformed metal polycrystals, conclusions for the local stress state within the grains of polycrystalline aggregates can be drawn. The expected slip systems can be calculated when the local stress tensor and the orientation of the crystallites in the specimen space are known. In fatigued nickel polycrystals, the crystal orientation was determined by the EBSD (electron backscattering diffraction) method in the scanning electron microscope. It was shown that at the relatively small plastic strains under fatigue conditions the crystalline interactions do not essentially influence the local stress state in the grains, but the external uniaxial stress tensor remains valid in good approximation.     

EM208型电镜的维护

本文介绍了EM208型电镜真空系统的特点,而采取相应维护措施的经验。     

大型氦低温制冷系统研究进展

低温超导技术在基础科学研究中的广泛应用,极大地带动了低温工程的发展.大型强子对撞机(LHC)、国际热核聚变实验堆(ITER)、先进实验超导托卡马克(EAST)、北京正负电子对撞机重大改造项目(BEPC-Ⅱ)所配套的大型氦低温系统,分别作为国际与国内最大的低温装置,代表了当今低温技术的最高水平.介绍了这4个典型低温系统的流程、性能指标以及运行情况,以及其它具有代表性的氦低温系统及其应用.     

冷氦换热器低温换热试验研究

为验证采用液氧对冷氦加温的可行性,研究光管、整体翅片管两种形式的换热器在不同流量、压力下的换热性能,开展了冷氦换热器的原理性试验和数值仿真研究.研究结果表明:相同工况下,整体翅片管换热效果比光管好很多,整体翅片管对强化换热效果明显,数值仿真结果与试验结果吻合较好.     

Properties of Electron Bubbles in Liquid Helium

We present calculations of a number of properties of electron bubbles in liquid helium. The size and shape of bubbles containing electrons in different quantum states is determined based on a simplified model. We then find how the geometry of these bubbles changes with the applied pressure. The radiative lifetime of bubbles with electrons in excited states is calculated. Finally, we use a quantum Monte Carlo method to determine the properties of a bubble containing two electrons. We show that this object is unstable against fission.     

Compression test of a single carbon fiber in a scanning electron microscope and its evaluation via finite element analysis

A longitudinal compression test for a single polyacrylonitrile-based carbon fiber (T300) was performed using a scanning electron microscope. The compressive stress/strain behavior was initially linear, but subsequently became nonlinear. The longitudinal tangent modulus decreased with increasing compressive strain. A cyclic compression test revealed that the T300 carbon fiber deformed elastically up to ~90% compressive strength. The variability in the compressive strength was evaluated using Weibull analysis. The representative compressive strength of the T300 carbon fiber was nearly the same as the tensile strength. The compressive strength of the T300 carbon fiber was almost same as that of the high-tensile strength T800S carbon fiber. Finite element analysis was performed to investigate the validity of the test method. The results showed that the longitudinal compressive stress on the carbon fiber varied during longitudinal compressive loading. The maximum longitudinal compressive stress in the carbon fiber was slightly higher than the average compressive strength applied at the end. However, the variability in the measured compressive strength was much higher than that in the longitudinal compressive stress on the carbon fiber, which does not affect the former.