氟化镁窗口氘灯的真空辐射衰减特性

针对真空环境下使用氟化镁窗口氘灯时,氘灯表面易受污染,导致氘灯的紫外-真空紫外辐射强度逐渐衰减的问题,对紫外-真空紫外波段辐射传递标准光源氘灯的真空辐射衰减机理进行了分析.在此基础上,研制了液氮制冷屏装置来抑制氘灯衰减.建立了氘灯真空辐射特性测试系统,利用该系统对液氮制冷屏装置的有效性进行了考察.测试结果显示,在160～300 nm波段,氘灯平均衰减率可由原来的7%/h下降为1%/h,表明液氮制冷屏装置能有效地抑制氟化镁窗口氘灯在真空环境下的辐射衰减.     

紫外-真空紫外辐射标准光源的比对

建立了高精度光谱辐射计量系统,给出了164～300nm波长间3个光谱辐射标准氘灯光源的比对结果.其中3个光谱辐射标准氘灯光源分别以德国国家物理技术研究院(PTB)BESSYⅡ同步辐射、英国国家物理实验室(NPL)Daresburg同步辐射、中国合肥(国家同步辐射实验室)同步辐射为标准标定.实验中采用相互交替的比对顺序、微机控制比对时间以及抛光氘灯端窗等方法有效的消除了系统误差.实验数据分析结果表明:3个光谱辐射标准氘灯光源的相对光谱分布,在各自给定的不确定度范围内相一致,这也间接的验证了各国建立的紫外 真空紫外辐射标准的一致性.实验中比对引进的误差为1.7%.同时也研究了氘灯的光谱辐射特性.     

空间紫外遥感仪器漫反射板真空紫外辐照特性研究

漫反射板漫反射率值的变化将直接影响空间紫外遥感仪器在轨辐射定标结果及探测结果。基于空间紫外辐照环境,构建了漫反射板真空紫外辐照特性研究装置,利用该装置对空间紫外遥感仪器AL+MgF2漫反射板的真空紫外辐照特性进行了研究。实验结果表明,真空紫外辐照加速了漫反射板漫反射率值的衰减;漫反射板在160-300nm整个波段出现衰减现象;衰减程度随辐照时间的增加不断增大;各波长处的衰减呈线性规律变化,衰减速率随波长的不同而不同。对可能引起衰减的原因进行了初步分析。     

真空紫外辐照对Lumogen薄膜损伤及光学性能的影响

为研究Lumogen(C22H16N2O6)薄膜在真空紫外波段的光致发光特性及辐照损伤,采用热阻蒸发法,以氟化镁为基底制备Lumogen薄膜.使用真空紫外荧光光谱仪、原子力显微镜(AFM)、扫描电子显微镜(SEM)、紫外?可见分光光度计等仪器分别对薄膜的光致发光特性、荧光强度衰减变化、表面形貌、透过率等进行测试与表征....     

紫外-真空紫外波段的Al+MgF_2膜

Al+Mg F2 膜是真空紫外波段常用的一种反射膜。根据薄膜光学的电磁场理论计算了正入射条件下 Al+Mg F2 膜在真空紫外波段的反射率随氟化镁膜厚度的变化规律。研究了 Al+Mg F2 膜的制备工艺 ,利用 Seya-Namioka紫外 -真空紫外反射率计测得 Al+Mg F2 膜的反射率在 1 50 nm～ 34 0 nm的波段上高于 80 %。Al+Mg F2 膜制备一年后 ,其真空紫外波段的反射率未有明显变化     

空间紫外遥感仪器漫反射板的真空紫外辐照特性

由于漫反射板漫反射率值的变化将直接影响空间紫外遥感仪器在轨辐射定标结果,因此,对各种影响因素进行了研究.基于空间紫外辐照环境构建了漫反射板真空紫外辐照特性研究装置,利用该装置对宅间紫外遥感仪器Al MgF2漫反射板的真空紫外辐照特性进行了研究.实验结果表明,真空紫外辐照加速了漫反射板漫反射率值的衰减,漫反射板在160～300 nm整个波段出现衰减现象;衰减程度随辐照时间的增加不断增大;各波长处的衰减呈线性规律变化,衰减速率随波长的不同而不同.文中对可能引起衰减的原因进行了初步分析.     

一种120～300 nm紫外-真空紫外激发/荧光光谱测量装置

介绍了一种可用于120～300 nm激发的荧光粉发射光谱,激发光谱和相对亮度测量的紫外-真空紫外单色仪/荧光光谱仪装置.发射光谱的测量范围为380～780 nm.该仪器由真空紫外光源、真空紫外光谱仪、样品室、真空泵、平像场荧光光谱仪、光电倍增管等部分组成.真空紫外光源采用Cathodeon公司的30 W氘灯,真空紫外光谱仪为美国ActonResearch公司的VM-502 0.2 m单色仪,CCD探测器采用日本滨松公司的S3921型自扫描二极管阵列.测试结果表明该仪器的光谱重复性和准确性好于1%,样品色坐标的重复性和准确性均好于0.001.     

紫外-真空紫外波段的Al+MgF2膜

Al+MgF₂膜是真空紫外波段常用的一种反射膜。根据薄膜光学的电磁场理论计算了正入射条件下Al+MgF₂膜在真空紫外波段的反射率随氟化镁膜厚度的变化规律。研究了Al+MgF₂膜的制备工艺,利用Seya-Namioka紫外-真空紫外反射率计测得Al+MgF₂膜的反射率在150nm～340nm的波段上高于80%。Al+MgF₂膜制备一年后,其真空紫外波段的反射率未有明显变化。     

紫外灵敏度测试装置

紫外波段的光谱辐射灵敏度是衡量紫外像增强管水平主要特性参数之一，本文讨论了紫外器件辐射灵敏度的测试原理、方法，及测试装置。     

紫外-真空紫外材料漫反射特性智能化测试系统

在光谱辐射定标中,漫反射元件是定标的重要组成部分.为此研究了铝漫反射板的制作工艺,以及漫反射材料漫反射特性的研究方法,应用双向反射分布函数BRDF(Bidirectional Reflectance Distribution Function)的概念,设计了一种基于五自由度转台的新型真空紫外漫射特性测试装置.测得正入射和30°入射条件下漫反射材料在紫外--真空紫外波段的漫反射特性,并对结果进行了分析.实验证明,铝漫反射板在紫外--真空紫外波段具有良好的朗伯特性.     

真空应用太阳模拟灯及其灯阵的研制

为了对某相机进行热平衡试验,并克服传统太阳模拟器结构复杂、成本较高、光效利用率低的缺点,提出了将太阳模拟灯阵整体放在真空罐内使用的研制方案。首先,对该方案所需解决的各种问题进行了理论分析,计算得出模拟灯阵的辐照度要求为635.2～905.4W/m2,光学系统效率为0.1444。分析了真空罐液氮冷却系统的导热能力,结果显示,该冷却系统温度升高ΔT为2.0741K,小于其过冷度4K,表明该冷却系统可以将太阳模拟灯阵灯的热量导出。对系统热设计进行了分析和讨论,结果表明,积分器和反射镜的温度在200℃左右,氙灯灯极温度在92℃左右,满足其长时间正常工作的条件。最后,测试了模拟灯阵的技术参数,结果显示其照度为490.37～1000.56W/m2连续可调,辐照不均匀度±5%,辐照不稳定度±5%/h,各项指标均满足设计指标要求。     

低温杜瓦装置的结构设计与传热分析

为了获得有效的超导磁体运行的低温环境,文中介绍了低温超导磁体杜瓦装置的结构设计和传热分析,研制了一套采用真空多层绝热、铜辐射冷屏、蛇形排气管结构形式的绝热系统.通过传热理论计算表明,液氦的损耗量小于技术要求的0.9L/h指标,能够保证超导磁体系统能够在一定的低温环境下长日时间的运行.     

Frozen-surface replicas of rat bladder luminal membrane

A method for preparing replicas of the luminal surface of frozen, unfractured but deep-etched whole bladder tissue using a Bullivant type II device is described. A small piece of glutaraldehyde-fixed (uncryoprotected) rat bladder is rinsed in distilled water, mounted luminal side uppermost on a specimen holder and rapidly frozen by immersion in liquid nitrogen (cooled below its boiling point in a vacuum) or by contact with a copper block at liquid nitrogen temperature. The specimen is processed in the type II device without fracturing and 'deep-etched' by allowing a longer period than usual to elapse before shadowing. The results are assessed with reference to the appearance of the luminal membrane in standard freeze-fracture replicas, and some preliminary observations on the structure of the normal luminal membrane and its counterpart in bladder tumours are presented.     

A simple pneumatic device for plunge-freezing cells grown on electron microscopy grids

A detailed design for a simple and inexpensive variable-speed (1.0–5.8 m s^?1) pneumatic plunge-freezing device is presented. Cultured cells, grown on Formvar-coated 75-mesh gold finder grids, are pneumatically driven into a stirring mixture of propane/isopentane (3:1) cooled by liquid nitrogen (LN₂). Premature freezing of the sample in the cryogenic vapors above the cryogen is prevented by plunging through an entry tube into an insulating box, to which a partial vacuum is applied. The cryogenic vapors are drafted into the box at the level of the liquid cryogen by the vacuum, thereby preventing a layer of cold gas from collecting above the cryogen. To prevent the sample from thawing during transfer from the cryogen to the substitution medium, the box top is removed and compressed air is forced through a corrugated tube running the length of the box. The resulting boiling LN₂ creates an atmosphere below ?120°C in which the transfer can be accomplished.     

A novel facility for ageing materials with narrow-band ultraviolet radiation exposure

A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter. Radiation at the wavelength range 250-500 nm is dispersed onto the sample plane of 1.5 cm in height and 21 cm in width. The optical performance of the device has been characterized by radiometric measurements. Using the facility, test samples prepared of regular newspaper have been irradiated from 1 to 8 h. Color changes on the different locations of the aged samples have been quantified by color measurements. Yellowness indices computed from the color measurements demonstrate the capability of the facility in revealing wavelength dependencies of the material property changes in reasonable time frames.     

An inexpensive device for freeze drying and plastic embedding tissues at low temperatures

The preparation of biological tissues for electron microscopy by rapid freezing retains the original localization of ions and molecules. A reproducible freezing regime was established by quenching tissues in liquid propane according to the method of Elder et al. (1981). Tissue was thereafter freeze dried in a custom built freeze drying device with a liquid nitrogen cooled stage to prevent ice recrystallization during drying. The device was also designed to allow the vacuum embedding of tissue in low temperature resin such as Lowicryl® and polymerization in situ. This paper describes the design of the device and an example of its use in the freeze drying of cartilage. The results show that minimal ice damage occurs to the chondrocytes and that intracellular organelles are clearly visible. The regime described may prove a useful and pragmatic alternative to cutting tissue in the frozen state. Translocation of elements is unlikely except perhaps in the case of very labile elements such as Na and K, but this remains to be fully elucidated.     

An HCN Interferometer for Measuring the Electron Density Distribution in the Plasma of the Л-2M Stellarator

A diagnostic setup for determining the electron density profile in the plasma of the -2M stellarator is described. An interferometer based on an HCN laser (337 m) with a mirror in a vacuum chamber and built according to the Michelson scheme is the main element of the setup. To translate the phase shift to a frequency range convenient for recording, a system with a mechanical frequency shifter based on the Doppler effect is used. InSb photoresistors cooled with liquid helium are used as radiation detectors. Seven mirrors are arranged in the vacuum chamber. Any of these can be included in the optical system of the interferometer by rotating an external mirror; scanning along seven chords is thus accomplished. The results are recorded in digital form. The subsequent data processing makes it possible to determine the parameters of the spatial density distribution functions belonging to an a priori selected family.     

Freeze-fracturing at low temperatures: I. A device for fracturing biological specimens at 77–10 K under high vacuum

Standard freeze-etching or freeze-cleaving is performed at 173 K in a vacuum of 133 μPa or at 77 K under liquid nitrogen with subsequent transfer of the specimen into a vacuum chamber. It has been suggested that the frequent poor resolution of morphological details, the poor complementarity of innermembrane protein particles and the semi-crystalline substructures in biomembranes are caused by structural distortion or plastic deformation due to sheer forces which occur even at 77 K during fracturing or cleaving. In addition, water contamination and radiant heat damage occurring during replication introduce artefacts to the structural record. These artefacts could be avoided or reduced by lowering the temperature at which fracturing or cleaving and shadowing is carried out, to about 10 K. Therefore, a device for cleaving biological specimens at 15–10 K under high vacuum was constructed. To allow the use of existing equipment, the device was built into a standard Balzers 301 vacuum unit, where the specimen transfer is done via an airlock system which allows hoar frost contamination free transport of the specimen holder onto the specimen table. To reduce or prevent the condensation of water and other residual gases in the vacuum onto the freshly cleaved specimen surface at 10 K, the specimen is surrounded by two cooled surfaces of 6 and 20 K. All condensable gases outside those shielding shrouds will condense on these surfaces before reaching the specimen. This makes it possible to work at a high vacuum of 3 μPa outside the cooled shrouds, which can be reached with standard turbomolecular pumps. The actual vacuum within the cooled shrouds is estimated to be approximately 13 nPa. Residual gas analysis before and during replication reveals equal conditions to ultra high vacuum systems. An analysis of the yeast cell paracrystalline plasmalemma structure shows that the topographic resolution of the crystalline arrays has been improved by working at 12 K. However, plastic deformation still occurs under these conditions. This observation points to the possibility that what is described as plastic deformation, for at least some membrane proteins, may be a loss of resilience at low temperatures.