真空计量标准的研制与应用

兰州物理研究所研制了一系列真空标准装置,可用于真空规、方向规、分压力质谱计、真空漏孔和正压漏孔的校准.其静态膨胀法真空标准装置、动态流量法真空标准装置及超高/极高真空校准装置是用于真空规校准的三套基础标准,覆盖的校准范围为(10-10～105)Pa;程控式真空规校准装置适用于工业部门,其校准范围为(10-4～105)Pa;为实现质谱计的校准,研制了一台具有三路相同独立进样系统的分压力质谱计校准装置,标准分压力通过磁悬浮转子规以两种不同的方法进行测量,该校准装置可实现(10-7～10-1)Pa范围内的分压力校准;为实现真空漏孔的校准,研制了恒压式气体微流量标准装置和固定流导法气体微流量标准装置.恒压式气体微流量标准装置的校准范围为(10-8>～10-2)Pa·m3/s,同定流导法气体微流量标准装置的校准范围为(10-10～10-5)Pa·m3/s,漏孔漏率的校准通过比较被校漏孔和标准气体微流量计在一台四极质谱计上引起示漏气体离子流的大小计算得到;为实现正压漏孔的校准,研制了一台正压漏孔校准装置,采用定容法和定量气体动态比较法对正压漏孔进行校准,校准范围为(5 × 10-5～10-1)Pa·m3/s;研制了一台定向流真空校准装置,实现对方向规的校准和非平衡态分子流的研究,装置的校准范围为(10-7～10-1)Pa.     

极高真空校准室内残余气体的成分分析

用四极质谱计对316L不锈钢制作的极高真空(XHV)校准室在烘烤前、后的残余气体成分进行了分析。一个热阴极电离规(IE514)和一个四极质谱计(QMS200)连接在XHV校准室上。烘烤前,开、关热阴极电离规以及对其进行除气,放出的气体主要有H2O、CO、H2、CH4和CO2。烘烤后,开、关热阴极电离规以及对其进行除气,放出的气体主要有CO、H2、CO2和CH4。整个烘烤过程完成后2h,XHV校准室内的压力在室温下通过分子泵串联抽气机组抽至8.97×10-9Pa,用四极质谱计分析到的残余气体成分主要为H2和CO。整个烘烤过程完成后4h,打开非蒸散型吸气剂泵(NEGP)对XHV校准室抽气,结果表明NEGP对H2具有较大的抽速,但对碳氢类化合物(如CH4)和惰性气体几乎没有抽速。用NEGP对XHV校准室连续抽气72h后,XHV校准室内的压力从8.34×10-9Pa下降到9.12×10-10Pa。不锈钢XHV校准室内的残余气体成分中大量的CO和CO2主要来自于四极质谱计。     

可测10^—^12Pa压力的离子谱规

从电子激发解吸(ESD)离子引起的测量误差出发,考察了。Lafferty 发明的热阴极磁控规和 Benvenuti 和 Hauer 改进的 Helmer 规的测量下限。在此基础上研制了一种新的热阴极全压规一离子谱规,它可以在低至10~(12)pa 的压力范围内完全避免 ESD 离子所引起的误差。其结构特点是:1.采用能使气相离子和 ESD 离子具有大的能量差的球形栅极离子源;2.采用具有高能量分辨率的180~(?)半球形离子能量分析器,以提高离子聚焦能力并降低 X 射线下限;3.采用可降低热阴极出气量的在铝合金法兰内掩埋离子收集极的技术。在一台新的铝制 XHV 系统上,进行了以 Mo 和 Pt 作栅极的两种新规的性能研究,通过引入 O_2进行实验证实了气相离子和ESD 离子的有效分离。对 Pt 栅规,当压力低至10~(-11)pa 时,可完全消除 ESD 离子误差。新规的测量下限和灵敏度分别为:Mo 栅规:Px<2×10~(-12)Pa,S=4.5×10~(-4)A/Pa;Pt 栅规:Px<5.6×10~(-12)Pa,S=1.8×10~(-4)A/Pa。     

四极质谱计测量高压力的一种方法

真空镀膜、半导体加工等真空工艺气氛的原位监测对产品质量至关重要。由于一般质谱计测量上限的限制,较高压力下的工艺气氛的气体分析只能通过取样的方法来实现。四极分析器中离子与分子间的碰撞散射是导致四极质谱计在高压力下测量非线性的主要原因。为此,以碰撞散射为基本假设,推导出四极质谱计测量分压力的普遍公式。提出了四极质谱计在较高压力测量的两步校准法,通过与全压力规的配合,解决了四极质谱计在较高压力非线性条件下测量的实用问题。实验结果表明:可将四极质谱计的测量上限从10~(-2)Pa左右提高一个多数量级。     

渡边文夫的极高真空测量研究评介

渡边文夫对极高真空（XHV）测量的系统而有成效的研究，受到国际同行的注目，其中最有实用价值和创新意义的是离子谱规，此规大大降低了X射线效应、电子激励解吸效应和热出气效应，可测量10-12Pa的XHV。本文试图较全面地评介渡边文夫的XHV测量研究工作，以资借鉴。     

碳纳米管阴极电离规结构的模拟优化设计

为了提升碳纳米管(CNT)阴极电离规的综合性能和实用性,本文利用离子光学模拟软件SIMION3D8.0和CAD建模软件构建了CNT阴极电离规的物理模型,且通过模拟计算得到不同电极结构参数对CNT阴极电离规各种性能的影响规律。研究结果表明,不同的阴极基座直径、门极尺寸产生不同的电子运动轨迹;电子运动路径随着外屏与阳极栅网之间距离的增大先增大后减小;电子逃逸率随着门极和阳极顶部间距的减小而逐渐增大;聚焦孔直径对正离子的收集影响显著,且气相离子/电子激励脱附离子收集比率在收集孔直径约为2 mm时达到最大。故选用合适的电极结构参数能有效地提高CNT阴极电离规的总体性能,延伸其真空测量下限。     

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10-8Pa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...     

热阴极电离规灵敏度的数值模拟研究

本文基于数值模拟和实验方法研究热阴极电离规的计量性能,开展了电极电压和栅网结构对Bayard-Alpert电离规灵敏度的影响研究.研究表明,随着阴极阳极电压差从50 V增加到140 V,灵敏度持续增大,之后缓慢下降,随着栅网丝间距从2 mm增加到3.5mm和丝径从0.4mm减小到0.2mm,灵敏度显著增大.采用正交分析...     

热阴极与冷阴极电离规稳定性的比较研究

电离规作为参考标准或副标准时,稳定性尤为重要。通常在校准服务中,只有热阴极电离规用作参考标准或副标准,不采用冷阴极电离规的传统原因是冷阴极电离规的非连续性、低压力下放电延迟效应以及它的不稳定性等。尽管现代反磁控型冷阴极电离规被认为解决了这些问题,但没有足够的数据来证明这些特性。作者介绍了对3个热阴极电离规和2个反磁控型冷阴极电离规的校准结果,校准采用的是高真空基础标准,校准范围为10-7～10-3Pa,校准气体包括N2、Ar、He和H2。在1×10-4Pa恒定压力下连续72h观测中,热阴极电离规在N2、Ar和He中的稳定性优于反磁控规,但在H2中所有规的稳定性相似。在6个月的重复校准中,所有规在N2、Ar和He中的长期稳定性相似,但在H2中反磁控规的长期稳定性优于热阴极电离规。对于不同的气体,反磁控规的非连续性出现在不同的压力点,反磁控规的非连续性使校准工作变得更为复杂。     

极高真空电离规的校准实验研究

介绍了2支反磁控型冷阴极极高真空电离规和1支热阴极极高真空电离规的校准实验研究结果。实验设备是一台极高真空校准装置,实验范围为10^-9～10^-1Pa,实验气体为N2。实验结果表明,尽管2次校准结果的重复性较好,但就单次校准结果来看,每个规的灵敏度（修正因子）的最大值和最小值之间的偏差较大。因此,极高真空电离规要得到准确的测量结果,对其进行精确校准是非常必要的。     

用Bessel-Box型能量分析器的离子规和四极质谱计的性能

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The electron-stimulated desorption ions from the ionizer of a quadrupole mass spectrometer

The species and the pressure dependence of the electron-stimulated desorption (ESD) ions from the grid surface of the ionizer of the quadrupole mass spectrometer were measured by the QMS with the Bessel-box-type energy analyzer (BB-QMS). The BB-QMS was developed in order to measure true mass spectra of gas phase without ESD ion effect in high to extreme high vacuum. The ESD ions observed in typical residual gasses such as water, carbon monooxide, oxygen and carbon dioxide were H⁺ (H₂O), O⁺ (H₂O, CO, O₂, CO₂), OH⁺ (H₂O). The intensity of the ESD ion signals showed saturation upon increasing coverage of the water molecules on the grid surface.     

Isotope ratio measurements with elemental-mode electrospray mass spectrometry

The isotope ratio capabilities of an electrospray ionization source interfaced to a quadrupole mass spectrometer are described. With the instrument operated in the metal ion mode, isotope measurements of Ag, Tl, and Pb are conducted using elemental ions produced from 1 × 10(-)(4) M solutions of metal nitrates or acetates in methanol. For Ag and Tl, spray conditions are identified that produce spectra free of MH(+) ions. Unbiased Ag and Tl ratio measurements with precisions of ～0.2% RSD are readily attained. Further improvement in relative precision appears to be limited by temporal drift in the degree of mass discrimination imparted to the measurements by the mass spectrometer. Isotopic analysis of Pb is greatly complicated by significant yields of PbH(+) polyatomic ions.     

An investigation of the factors affecting the performance of the quadrupole mass spectrometer with particular reference to residual gas analysis

The results of an experimental investigation into the factors limiting the performance of a conventional quadrupole mass filter are presented. The number of cycles of the rf field which the ions experience in travelling the length of the quadrupole is shown to be the factor limiting resolution under any given set of operating conditions. The design of an RGA is discussed in detail and it is shown that an analyzer only 2 in. long is adequate to achieve the required resolution giving at the same time a high sensitivity. This enables a small mass spectrometer to be designed capable of being fitted into a vacuum system as easily as an ionization gauge. This instrument will resolve perfectly individual peaks up to 50 amu with a limit to the detection of partial pressure of better than 10⁻¹¹ torr.     

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.     

四极质谱计校准和应用研究系统

为了满足对四极质谱计定量分析的需求,建立了一台四极质谱计校准与应用研究系统。该系统可用于四极质谱计分压强灵敏度及图样系数的校准和四极质谱计稳定性的研究,并可用作演示系统。为实现在各种应用条件下的分析应用,本系统采用四种进样系统,把四极质谱分析器与被测系统连接起来,即超高真空条件下直接进样、10~(-2)～10~2Pa压强分析时的分子流动态进样、高压强下直到大气压的毛细管进样以及微量气体分析时的静态或准静态进样系统。     

四极质谱计灵敏度与离子源参数关系的实验研究

本文通过改变QMS4 2 2型四极质谱计离子源的发射电流、阴极电压和聚焦电压等参数值 ,测量了质谱计灵敏度的相应变化 ,给出并分析了实验结果。实验结果表明 ,对质谱计离子源参数进行调节 ,可以优化质谱计的灵敏度并使之达到最大值