分流式超高真空电离规

本文提出一种电极采用“端流式”结构的调制型BA规的设计,可用于超高真空测量。它的灯丝和离子收集极分别置于加速栅的两端,而调制极为围绕收集极的环形圆片。使用时采用调制极电位由阴极电位跳变到收集极电位的工作模式,此时收集极得到的离子流占总离子流的份额发生变化,而它的光电流却并不随调制极电位而异,由此可基本上克服加速极软x射线的影响。实验得到这种规的灵敏度为30托~(-1)及15托~(-1),即调制系数达到50％。测量下限约4×10~(-12)托。     

电离规离子流可编程增益放大器的设计

采用前置微电流放大器和可编程增益放大器两级运放,实现电离规离子流的可编程增益放大,以满足在真空度迅速变化且动态范围较宽时对真空度的快速准确测量。介绍了微弱电流信号的放大原理、器件选择原则、单片机控制可编程增益放大器的实现方法、电路抗干扰措施等,并给出了部分测试结果。本文设计的电离规离子流放大电路具有增益动态范围宽、精度高、响应速度快等优点,为托卡马克装置的真空度快速测量系统中离子流测量电路提供了设计参考。     

聚变强磁场下真空测量电离规结构及阴极灯丝优化研究

基于强磁场环境中托卡马克装置偏滤器中性粒子压力快速测量,使用普通热阴极电离计,难以实现托卡马克偏滤器实验运行的原位精确测量.文章针对普通热阴极电离计的结构特点,首先探究了强磁场下,阴极发射电子的运动轨迹受磁场约束对规管灵敏度的影响.应用有限元方法,计算分析了阴极灯丝受电动力以及热应力和电动力耦合作用下发生形变的规律,得到阴极灯丝应力、总变形量和轴向变形量数据以及阴极灯丝的热力性能不受加热电流变化影响的结论.提出可在强磁场下稳定工作的规管结构设计方案,得到阴极灯丝优化结果,为聚变装置强磁场下真空测量快规的优化设计提供参考.     

热阴极电离真空计的误差

电离真空计规管及其控制单元。都有各自的各项误差。本文讨论作为电离计整体的误差与各项误差的关系。 电离计的压强读数可用下述公式表达;式中:i+──为收集极离子流; i──为发射电流; k──为规管系数. 白误差传递公式(1)可得到压强的示值 (相对)误差Ep的表达式: E2=E2H+E2I+E2i-(2)式中Ek、Ei+和Ei-分别为规管系数,离子流和发射电流的相对误差。下面分别讨论这三项误差。 1.规管系数的误差 规管测量的对象往往含有氧气、水蒸汽或其它污染性气体,电极及玻壳往往受到氧化或污染。这样规管系数在寿命过程中会逐渐变化。使用后的规管比…     

弹道电离规的性能研究

经过最近的工作,我们对弹道规的性能有了较深刻的理解,并且对这种规管作出了重大的改进。灯丝和中央场之间的耦合是控制线性、灵敏度和振荡的一个主要因素。从灯丝上发射出正离子、能量过大的电子到达离子收集极以及Ｘ－射线光电流,是在低压强下引起误差的一些因素。现在的这种设计是非常简单的,在规管内部,干扰压强测量的结构比较少。规管的灵敏度提高为原来的四倍,所以,为了产生 Ｂ－Ａ规在８ｍＡ发射电流的条件下所得到的离子流,现在只需要１ｕＡ的电子流。此规管的输入总功率小于１００ｍＷ。在１０－１１乇－１０－５乇范围内,离子流与压强的关系是近似线性的。在非弹道型的工作条件下,线性区域可延展到１０－２乇。     

碳纳米管阴极电离真空计研制及其性能研究

碳纳米管阴极电离真空计在超高/极高真空测量中具有广阔应用前景,基于碳纳米管阴极研制了测量范围10-9~10-4Pa的电离真空计,真空规管包括了碳纳米管阴极、门极、阳极、反射极和收集极,电路控制系统由高压电源、微弱离子流测量和控制电路组成。实验研究结果表明,不锈钢衬底上直接生长制备的碳纳米管阴极性能良好,开启场强和阈值场强分别为1.9 V/μm和3.9 V/μm,当阳极电流为42μA时,碳纳米管阴极电离真空计本底干扰可降低到1.81×10-9Pa。     

能量分析器型真空电离规性能研究

电子激励脱附(ESD)效应和软X射线效应是影响电离真空计测量下限的两大重要因素。基于能量分析器研制了电离真空规,在极高真空校准装置上对其开展性能研究,包括不同压力或不同阴极发射电流下的离子流、ESD效应和软X射线影响。结果表明,系统压力介于10^-8 Pa和10^-6 Pa之间,当气体发生电离,能量分析器电压在低于阳极电压约25 V时收集极能得到最大的气相离子流。系统压力在10-7~10^-8 Pa量级,采用2.5 mA的发射电流可得到比1 mA更大的气相离子流值。分离气相离子与ESD离子的能量筒电压差约为30 V,规管栅极除气后可降低ESD效应至除气前的37.5%。电离规的软X射线带来的本底干扰对应等效压力约为9×10^-11 Pa。     

一种正弦波连续调制真空电离规

在轴向发射真空电离规结构基础上，研制了一种新的正弦波连续调制真空电离规。本规将磁控管和潘宁放电的工作方式结合在一起，使得发射电子的轨道加长，规管具有较大的灵敏度（对氮气约为０１６．０托－１），较低的发射电流（不超过１００微安）。规在工作时，稳定性良好。由于正弦波连续调制技术的引进和轴向外加磁场的作用，将该规的压强线性测量下限拓展到１０－１１托。     

调制规的特点

1.序言无磁场的热阴极电离真空规作为一种压力测定装置在超高真空中具有很高的可靠性,是该范围中应用最广的真空规。但是还遗留几个必须解决的问题。它的原理是使从热灯丝发射的电子在栅极附近振荡,当振荡电子碰撞气体分子时,所产生的正离子被收集极收集。根据离子流去求出气体分子密度(或:压力),振荡电子最终与栅极碰撞,会产生两种副作用现象。     

极高真空测量中微小离子流检测技术研究

为解决极高真空测量中电离真空计微小离子流的检测难题,设计采用精密运算放大器组成电流电压转换结构,配合低通滤波、零点调节以及相位补偿等技术,实现了10~(-14)A微小离子流的准确检测。通过与国内外不同型号电离真空计进行试验测试,验证了该设计电路能够准确检测10~(-9)Pa极高真空下的电离真空计离子流,为实现极高真空测量设备国产化提供了技术参考。     

装有贝塞尔盒型能量分析仪的电离规和四极质谱计的研制

贝塞尔盒型能量分析仪由三部分组成 :一个圆筒形电极、一个中心圆盘和两个带中心孔的侧板 ,该分析仪结构简单、结实 ,十分适用于电离规和四极质谱计上。对电离规而言 ,分析仪被放置于电离器及离子收集器之间。在栅型电离器中所产生的离子被分离并注入到能量分析仪中。分析仪依据其激发的能量把电离器中产生的气相离子和栅网表面上脱附的电子激励解吸的离子分离开。如果应用一个法拉第杯型离子收集器和一个灵敏的直流放大器来进行离子流测量的话 ,那么该电离规测量范围在 10 - 1 0 ～ 10 - 3Pa之间。当二次电子倍增器采用脉冲计数方法时 ,所测量的压力范围在 10 - 1 1～ 10 - 6 Pa之间 (Ax TRAN,ISX2 ,U L VAC公司 ) .其典型灵敏度对氮气而言为 (6 .7± 0 .2 )× 10 - 3Pa- 1 和对氢而言为 (2 .3± 0 .0 4 )× 10 - 3Pa- 1 。对四极质谱计而言 ,能量分析仪被置于在电离器和四极滤质器之间。装有该分析仪的质谱计 ,给出了没有电子激励解吸离子的简单质谱。该分析仪能使四极质谱计的离子收集器免受从栅网表面发射的 X射线的辐射 ,和从电离器中的离子以及被激发的分子在退激励过程中释放的紫外线的辐射。这种屏蔽作用改善了在 10 - 3Pa范围内的气体中微量杂质的检测极限 ,使之降至亿分之几     

An improved ion gauge with gold coated electrodes for reliable operation in reactive gases and for use as reference standard

The ion gauge described here eliminates sources of error which cannot be removed with the grid-type ion gauge, for example, variation of the grid electron transparency, unstable mean ionization path length of the electrons, and losses of ions by exterior electrostatic fields and by ion pumping. In the pressure range from 10^?7 to 10^?1 Pa the response of the new ion gauge shows a high reliability. The gauge is operable in hydrogen without problems. The latter aspect is of interest for pressure measurement in equipment used for charged particle acceleration and storage, and for fusion experiments. The ionization gauge, in the form of a nearly closed system with pure gold layers on the electrodes, shows the following remarkable advantages with respect to grid-type gauges. (a) Shielded volume for effective ion formation, no influence of exterior electric fields. (b) Well defined and limited ionization path length for electrons. (c) Controlled heating of the gold plated electrode system during the operation at 250°C which diminishes disturbing effects by adsorbable gases and provides the same gauge coefficients in immersed or tubulated position—reduced variation of transpiration effects by changes of filament heating power. (d) A stable work function on the gold ion collector surface secures good long term stability of gauge coefficient. (e) V-shaped ion collector combines extension of linearity at high pressures by reducing space charges with a low X-ray limit. (f) Negligible ion pumping; undisturbed operation with hydrogen. Noteworthy and new, the grid is insulated from the anode cylinder. Thereby the interfering effects of the usual large variations in the grid electron transparency on the ionizing current may be eliminated. This results in high accuracy and stability of the gauge coefficient over nearly 5 pressure decades. The X-ray limit p_x is approximately 2 × 10^?7 Pa (H₂). Construction and operation mode of the new screened ion gauge has been presented already in Gentsch and Messer, Proc 8th Int Vac Congr, Cannes 1980, p. 203; the version described here was improved by the use of tungsten as supporting material instead of platinum-iridium alloy.     

KJY-II型精密孔径仪的测量不确定度分析

KJY—Ⅱ型精密孔径仪是测量环规内径的专用仪器，已经在环规计量检定规程中(JJG894—95)被推荐为检定二等环规的首选仪器。本文着重分析了仪器的不确定度问题。     

Modulating ion current pressure gauge

A remote pressure measurement system suitable for ultra-high vacuum in a very severe noise environment, such as found in high energy accelerators, is reported. The pressure in a beam pipe of the 12 GeV proton synchrotron at the National Laboratory for High Energy Physics has been measured with high accuracy by a newly developed hot-cathode extractor type ionization gauge, here called the modulating ion current gauge. The output signal from the gauge head was sent to the synchrotron subcontrol room by a 120 m long cable and the measurement was carried out with full beam in the synchrotron. The miniaturized gauge head has a hemispherical mesh anode and a cylindrical electrode between the ionization region and the ion-collector to modulate the ion current. The modulated signal is sent to an amplifier via a double shielded coaxial cable and after amplification is detected with a phase sensitive detector. This new gauge can reject externally induced noise. The effects both of ions desorbed by electron-impact from the anode and of X-ray photocurrents from the ion-collector can also be avoided.     

电离规的新进展

介绍了传统热阴极电离规和冷阴极电离规的发展历程和研究现状、新型场发射阴极(微尖型阴极和碳纳米管阴极)在电离规中的应用、小型化电离规的发展和国内在超高/极高真空电离规研究方面取得的成果和现状。重点回顾了碳纳米管阴极电离规和小型化电离规在近年来取得的重大成就。由于碳纳米管具有长径比大、曲率半径小、机械特性强、导电性好和优异的场发射特性,使得其作为电离规阴极有望解决传统冷阴极电离规在低压下不能放电的困难和传统热阴极电离规的热出气效应,从而为极高真空测量提供一种解决途径。     

Ionization vacuum gauge with a carbon nanotube field electron emitter combined with a shield electrode

The applicability of carbon nanotubes to an electron source for a Bayard-Alpert type vacuum gauge has been investigated. Three gauge configurations are designed to optimize the gauge performance. The optimized gauge, in which an additional shield electrode is fixed on a gate electrode, exhibits good measurement of linearity between ion current and system pressure from 10⁻⁷ to 10⁻² Pa. A gauge sensitivity of 0.05 Pa⁻¹ has been achieved under 100 μA emission current for nitrogen, comparable with 0.07 Pa⁻¹ of commercial ionization gauges.     

Die Entwicklung der Totaldruckmessung im Ultrahochvakuum- und Extremvakuumbereich

Almost 60 years ago it was possible to produce ultrahigh vacuum (uhv), but only by the development of a special type of a hot filament ionization gauge by Bayard and Alpert it was possible to measure these low pressures continuously. Reasons for the lower limit of pressure measurement are mainly the photelectron current, produced by a soft x-ray radiation from the anode, and the electron simulated desorption of ions at the anode. Constructions of hot filament ionization gauges, which are able to measure even extreme high vacuum (xhv) by reducing these effects are discussed. The extreme low ion currents, which are to be expected in the xhv-region, can be measured with the help of continous secondary electron multipliers. Special types of cold cathode ionization gauges are also useful for the pressure measurements in the uhv-region.     

碳纳米管冷阴极超高真空鞍场规的电场模拟与实验研究

在静电鞍场规的基础上研制了一种碳纳米管(CNT)冷阴极鞍场规(SFG).这种冷阴极鞍场规具有电极尺寸小,吸放气率低,热效应低,功耗低的特点.本文首先计算了碳纳米管冷阴极鞍场规的电场分布,计算结果表明,二极型碳纳米管电子枪的引出栅极的正电位在低于100 V的情况下对环形阳极鞍场规的轴向电位分布影响很少;并且在现有条件下对规管参数进行了测试,实验测定的规管对空气的灵敏度是1.05 Pa-1,规管功耗由热阴极规的0.9瓦减小到7毫瓦.     

Atmospheric pressure ionization in a miniature mass spectrometer

A miniature cylindrical ion trap mass spectrometer featuring an atmospheric pressure interface allowing atmospheric pressure chemical ionization and electrospray ionization is described together with its analytical performance characteristics. The vacuum system, ion optics, mass analyzer, control electronics system, and detection system have all been designed and built in-house. The design is based upon a three-stage, differentially pumped vacuum system with the instrument capable of being interfaced to many types of atmospheric pressure ionization sources. Ions are transferred through home-built ion optics, and instrument control is achieved through custom-designed electronics and LabView control software. Corona discharge ionization and electrospray ionization sources are implemented and used to allow the analysis of both gaseous- and solution-phase samples during the characterization of the instrument. An upper mass/charge limit of approximately 450 Th with unit resolution was achieved using a 2.5-mm-internal radius cylindrical ion trap as the mass analyzer. The specificity of the instrument can be increased by employing the MS/MS capabilities of the ion trap and has been demonstrated for nitrobenzene. Limits of detection for the trace analysis in air of the chemical warfare agent simulant methyl salicylate (1.24 ppb) and for nitrobenzene (629 pptr) are achieved. The dynamic range of the instrument is currently limited to approximately 2 orders of magnitude by saturation of the detection electronics. Isolation and collision-induced dissociation efficiencies in MS/MS experiments both greater than 50% are reported. Electrospray/nanospray data are presented on solutions including 100 microM (D,L)-arginine, 10 microM (-)-ephedrine, and 10 microM lomefloxacin.