Field emitter-based vacuum sensors

The subject of this article is to review the current state of the art and the trends of the development of vacuum gauges using various types of cold-cathode electron sources (e.g. silicon field-emitter arrays, emitter arrays of the Spindt-type, carbon-based field emitters, MIM cathodes, p-n junctions). Recent progress in design and fabrication of novel vacuum pressure sensors based on field-emitter cathodes is described and discussed. The advantages and the problems of such gauges are briefly reviewed.     

A thermocouple vacuum gauge for low vacuum measurement

The construction of a thermocouple vacuum gauge for the range of pressures from 200 to 800 mbar is reported. The gauge differs from similar ones that cover the medium vacuum region. The main difference is that the thermocouple is not fixed to the filament, as usual, but is placed at some distance from the filament.     

Microstructured vacuum gauges and their future perspectives

New prototypes and concepts of microstructured vacuum gauges have been developed by using the fabrication technologies for micro electro mechanical systems (MEMS). The realization of such microstructured gauges requires sophisticated fabrication processes such as thin film deposition, photolithography and etching techniques. This approach of MEMS vacuum gauges is demonstrated by a few examples.Micro-Pirani gauges are based on the principle that the heat transfer between two surfaces is proportional to the number of molecules (and hence the pressure) transferring the heat, when the mean free path in the gas is larger than the distance between the surfaces. In contrast to conventional Pirani gauges with heated thin wires, in a micro-Pirani gauge the heat transfer takes place between an extremely thin heated membrane and the surrounding. The thin membrane (200-nm thick) is realized by deposition of siliconoxide/siliconnitride, photolithography and anisotropic etching of silicon wafers. Heating is performed by a meander-shaped aluminum thin film heater in the center of the membrane. This micro-Pirani gauge shows a high sensitivity in the pressure range between 10⁻⁴ and 100 mbar. By using a silicon “microbridge” with 10 μm small gap between heated membrane and surrounding, the pressure sensitivity of the chip is extended up to 1000 mbar.Similar concepts are presented and discussed with respect to the miniaturization of spinning rotor gauges. The new concept is based on the application of microfabricated disks (instead of spheres) and of electrostatic instead of magnetic driving forces. The extension of the sensitivity range for miniaturized spinning rotor gauges is also discussed.Finally, new perspectives for mechanical vacuum gauges are demonstrated. By application of micromechanical processes, very thin stress-compensated membranes can be fabricated which enable sensitive mechanical gauges even for pressures in the high vacuum range. First, experimental results with respect to these membranes are represented.     

低温绝热容器中皮拉尼真空计取代热偶真空计的可行性分析

在低温绝热容器夹层真空度的测量中,皮拉尼真空计和热偶真空计较适用,目前热偶真空计应用较多。从测量范围、测量精度、测量温度、互换性、远程监控、检漏能力和性价比等方面,对皮拉尼真空计和热偶真空计的性能进行了比较,得出皮拉尼真空计更适用于低温绝热容器夹层真空度测量的结论。最后列举了目前国外几种典型的商用皮拉尼真空计和热偶真空计的技术参数。     

《真空工程技术》一书已出版

由东北大学徐成海教授任主编，巴德纯教授（东北大学）、于溥教授级高工（沈阳真空技术研究所）、达道安研究员（航天部510所）、张世伟副教授（东北大学）任副主编的《真空工程技术》一书于2006年9月由化学工业出版社出版。全书约200万字，共一册32章，内容包括真空技术基础、真空泵、真空测量仪器、真空阀门、密封等零部件以及真空容器和真空系统设计计算等和真空技术在各工业领域中的应用，包括冶金、热处理、     

前苏联高真空扩散泵统一系列工作的回顾

详细地介绍了前苏联1953年由国家制订的高真空油扩散泵工业产品的统一系列。该系列包括五种规格,在入口压力为1×10-4~1×10-5Torr(1 Torr=133Pa,下同)范围内,对空气的抽速为100~8000L/s,用Д-1A号泵油获极限压力为(2~5)×10-6Torr。以后又补充一台H-40T大泵抽速为32000L/s。抽速100和500L/s的泵为二级喷咀;抽速为2000、5000和8000L/s的泵为三级喷咀,而32000L/s的大泵出口连接一台БН-3型油增压泵。所有这些泵的最大出口压力不低于0.1Torr,因此前级泵可直接用机械真空泵,不必用增压泵即能正常工作。1990年按国际标准口径又研制了新系列产品,性能有所改进。本文对目前我国生产高真空系列扩散泵有一定的参考价值。     

单双级旋片真空泵的自动转换装置

讨论了传统双级旋片真空泵的不足，论述了用串并联方案提高双级旋片真空泵的性能，并提出了实现双级旋片真空泵串并联的两种可行的方案，从而使泵的性能得到更大的提高。     

Optimized rotor pitch distributions for screw spindle vacuum pumps

Screw spindle vacuum pumps are characterised by a high suction performance and the ability to achieve high pressure ratios. Screw spindle vacuum pumps have varying progressions for the rotor pitch gradient, depending on the manufacturer. From a scientific point of view, the question arises which rotor gradient along the rotors has to be preferred for a particular set of operating conditions with reference to the machine characteristics. To answer this question a simulation of the compression process in the screw spindle vacuum pump is performed. The simulation program is used to calculate an energy-specific optimal rotor pitch applying an evolutionary optimization approach. It turns out that - in contrast to actually available rotor geometries - a continuous increase in rotor pitch from the pressure to the suction side is not ideal. An optimized rotor pitch curve is presented and the underlying physical dependencies are clarified by means of pressure and mass flow diagrams.     

A vacuum sensor using field emitters made by multiwalled carbon nanotube yarns

A newly developed vacuum sensor using carbon nanotube (CNT) field-emission has been designed. The fabricated device is an ionization gauge with a silk-like CNT yarn cathode, and the vacuum is indicated by the ratio of the ion current to the electron-emission current. The metrological characteristics of the sensor were studied in a dynamic vacuum system. It showed good linearity ranged from 10⁻⁴ to 10⁻¹ Pa. Taking advantage of the field-emission cathode, the power consumption is only about 5.5 mW. Moreover, comparing it to the conventional thermionic cathode, the CNT yarn cathode is more miniature and a cold cathode with no obvious thermal outgassing effect. Due to these features, the sensor described here could have potential applications in measuring vacuum inside sealed and miniaturized devices.     

气冷式直排大气罗茨真空泵及机组的热平衡计算

气冷式罗茨真空泵需要携带泵外换热器，以保证泵在高压差下正常工作而不会产生过热，热平衡计算是泵及机组成功设计的关键，本文对热平衡计算进行了探讨，研究表明，气冷式罗茨真空泵的温升，取决于工作气体本身的性质以及泵排气口压力与进气口压力的比值（即压缩比）。     

采用流量计测量复合分子泵抽速装置研制

本工作研制了一台采用流量计测量复合分子泵抽速的装置.本装置由测试台车、机柜、计算机自动控制和数据采集处理系统三部分组成.选用3个高精度流量计,满量程分别为1000 sccm、100 sccm和10 sccm,并联组成流量计组件用于测量输入气体的流量,选用高精度的复合真空计测量真空测试罩内气压.抽速测试结果显示,一台1200 L/s的复合分子泵N2抽速重复测量5次,14个气压测试点对应的抽速的最大相对标准偏差小于2％,重复性好.抽速测量的误差主要由流量计和真空计的系统误差决定.采用流量计测量一台分子泵在气压2.00×10-3 Pa～2.00 Pa范围的抽速,测量时间20 min以内.     

MEMS气敏传感器

随着MEMS技术的飞速发展，各种MEMS器件和系统相继问世，MEMS气敏传感器是其中之一。本文重点介绍了7种MEMS气敏传感器。     

Field-emission electron source for vacuum micropump

In the work a conception of a miniature, orbitron ion vacuum micropump for an integration with vacuum MEMS devices is presented. It is made of silicon and glass using microengineering technology. The main part of the device is a lateral field-emission source of electrons, which has been fabricated on oxidized silicon wafer. Both, cold cathode and anode of the source are made of thin gold layer using only one photolithography process. Fabrication process and the preliminary results of electrical tests of the field-emission electron source are presented. Experimental studies have shown its good emission parameters: a low threshold voltage (over a dozen Volts), a high electron current (from tens to several hundred micro amperes), and field enhancement coefficient from 10⁷ to 10⁸ cm⁻¹. These results are promising and give possibility to fabricate orbitron micropump as an integrated part of vacuum MEMS.     

新的真空泵抽速特性系数及其应用

给出了以真空泵抽速特性系数表示的抽速计算公式，以实例说明如何求值和选定真空泵抽速特性系数，最后说明真空泵抽速特性系数应用。     

机械真空泵的维修

本文为《实用真空技术》一书的核心章节 ,作者认真总结了工人师傅的丰富维修经验 ,理论与实践相结合 ,对真空泵的维修技术作了全面、系统、深入细致的论述 ,对读者有参考价值。     

方坯连铸RH真空装置真空泵控制系统

介绍攀钢方坯RH精炼装置真空系统基本控制功能,侧重介绍真空泵系统的功能和其相关系统控制.     

多级爪型干式真空泵原理分析

多级爪型干式真空泵的结构对于其材料消耗、体积、能耗等性能有着非常重要的作用。本文介绍了北京朗禾科技的最新型结构——螺旋反爪结构,就其原理和国际上最经典的两种结构:螺旋型(德国)和反爪型(英国)做了介绍和对比,说明螺旋反爪结构可以大幅度缩短泵的长度、节约大量的材料、提高抽气效率、降低加工精度、提高抽气性能,对爪型干式真空泵的发展和普及有很好的推动作用。     

常用真空计的测量范围及其性能

介绍几种测量范围为10-8～105 Pa的常用真空计,其应用十分广泛,性能较好,价格较低.     

机械真空泵的维修

本文为《实用真空技术》一书的核心章节，作者认真总结了工人师傅的丰富维修经验，理论与实践相结合，对真空泵的维修技术作了全面，系统，深入细致的论述，对读者有参考价值。     

机械真空泵的维修

本文为《实用真空技术》一书的核心章节，作者认真总结了工人师傅的丰富维修经验，理论与实践相结合，对真空泵的维修技术作了全面、系统、深入细致的论述，对读者有参考价值。