A UHV standard with option to be used as partial pressure standard

Abstract

Partial pressure measurement has become indispensable for many applications and contributes to the complete characterization of a vacuum system. In this work, an ultrahigh vacuum (UHV) standard was established for calibrating partial pressure analyzers as a partial pressure standard, and a new method was introduced to generate standard partial pressures, which was named 'the dynamic expansion method based on static expansion vacuum standard injection mode'. The method can produce standard partial pressures in the range from 10 -5 Pa to 10 -10 Pa. The relative standard uncertainty budgets of generated partial pressures (k = 1) were in the range from 2.8% up to 5.0% from 10 -5 Pa to 10 -9 Pa for nitrogen. Employing this method, the sensitivity calibrations of quadrupole mass spectrometry (QMS) were performed in the partial pressure range of 8.62 × 10 −5 Pa to 1.51 × 10 −10 Pa with single inert He, Ar, and Kr gas in secondary electron multiplier (SEM) mode. Similarly, the calibrations were carried out using active gases (H 2 , CH 4 , N 2 , O 2 , and CO 2 ) in the range 8.56 × 10 −5 Pa to 1.50 × 10 −9 Pa. Additionally, the SEM gains were calibrated for these high-purity gases, on the basis of SEM gain coefficients. QMS sensitivities equivalent to Faraday cup mode were attained, and it was found that the results were approximately consistent with those of previous studies. The data were also in agreement with our theoretical calculation values excluding CH 4 .

A study of the gas interference effects in quadrupole mass spectrometer

“…The measurement apparatus is illustrated schematically in figure 1. The device can be divided into two major parts according to the needs of the experimental research; namely, the UHV standard partial pressure generation system and three standard leaks, where the UHV partial standard mainly consists of the gas supply and static expansion system plus the dynamic system, which are described in detail in [14] and [15]. The standard leaks include two mixed gas leaks from LACO (total leak rate: 9.02 × 10 −7 Pa m 3 s −1 with 95% Ar, 1% H 2 , 1% N 2 , 1% He, 1% Kr, 1% Xe; total leak rate: 9.04 × 10 −7 Pa m 3 s −1 with 88% H 2 , 9% CO, 3% CO 2 ) and one pure helium leak from INFICON with a leak rate of 4.94 × 10 −8 Pa m 3 s −1 .…”

“…) and V 3 /(V 3 + V 2 ) have been measured as 1.07 × 10 −2 and 9.43 × 10 −1 , respectively. The conductance ratios C 1i /C 2i for nitrogen, argon and helium were calculated from equations ( 2)-( 4) based on the exponential fitting of the experimental results in [14]:…”

“…Since the secondary electron multiplier has the disadvantage of gain degradation with time, it needs to be checked fairly often. The Faraday cup detector was chosen in this experiment, while the other specifications are listed in tables 1 and 2 of [14] and [15]. Before investigating the interference effects of the gas mixture, the 12 h short-term stability of the leakage rate for the two reference mixture leaks was tested.…”

Applications of Vacuum Measurement Technology in China’s Space Programs

“…For example, onsite measurement of the Moon surface requires instrument with lower limit of 10 -10 Pa. In order to cover the partial pressure calibration range of UHV and XHV, a new partial pressure standard, with the so-called "dynamic expansion method based on static expansion vacuum standard injection" mode, has been developed in LIP [81]. Figure 20 shows the scheme of the standard.…”