Effects of Mechanical Tolerances on QMF Performance for Operation in the Third Stability Zone

IEEE Trans. Instrum. Meas.

Cheung

et al. 2010

Self Cite

Size reduction in quadrupole mass spectrometers (QMSs) is an ongoing requirement driven by the needs of space exploration, portable, and covert monitoring applications. Microelectromechanical systems (MEMS) technology provides a method of achieving this size reduction. A quadrupole mass filter (QMF) is one component of a QMS and is suitable for microfabrication. MEMS manufacturing techniques are more suitable to the production of rectilinear electrodes, instead of the more widely used circular electrodes. Present understanding of the performance characteristics of rectilinear electrodes and the dependence of these characteristics on electrode geometry are not well documented. In this paper, we report on the performance characteristics of a square-electrode QMF. Both the predicted performances obtained by computer simulation and experimental data are presented for operation in stability zone 1 (0.236, 0.706) and zone 3 (3.16, 3.23). A comparison between these results and the simulated data for equivalent devices constructed using hyperbolic and circular electrodes for operation in zone 1 is also made. This comparison demonstrates that, although the field produced by square electrodes is far from the "ideal," it is still possible to achieve useful filtering action. Our results also show that, for operation in zone 3, performance comparable with that of hyperbolic and circular electrodes operating in zone 1 is achievable.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Performance Characteristics of a MEMS Quadrupole Mass Filter With Square Electrodes: Experimental and Simulated Results

IEEE Trans. Instrum. Meas.

Cheung

et al. 2010

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“…Analytical techniques have found the same value of 1.128-1.130 for the r/r 0 ratio for operation in Zone 1 [12]. It was later found that this value is almost the same for operation in Zone 3 of the Mathieu stability diagram [15], [16].…”

Section: Introductionmentioning

confidence: 83%

Simulation of a QMS Including the Effects of Pressure in the Electron-Impact Ion Source

Sreekumar

IEEE Trans. Instrum. Meas.

2012

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This paper is concerned with the computer modeling of a quadrupole mass spectrometer (QMS) to include the effect of pressure in the ion source. The paper simulates the spectra over the pressure range from 10 −6 to 10 −4 mbar. An important contribution is the development of a novel procedure to include pressure dependence of the ion source to allow better prediction of instrument performance. Electron-impact total ionization cross sections in the ionic current expression are calculated using the binary-encounter-Bethe theory for argon gas. The predicted results show good agreement with the experimental results obtained from a commercial QMS used for residual gas analysis.Index Terms-Binary-encounter-Bethe (BEB), electron-impact ion source, gas measurement, ionic current, partial pressure, quadrupole mass spectrometer (QMS), quadrupole mass spectrometry, residual gas analyzer.

“…The program calculates ion trajectories by solving the Mathieu equations using a fourth order Runge-Kutta algorithm. Our approach has been described previously [15,16]. Generation, display, and storage of mass spectra and individual ion trajectories, together with parametric sweep control, are provided by the QMS2-Hyperbolic program.…”

Section: Methodsmentioning

confidence: 99%

“…We have used our previously reported simulation techniques [15,16] to investigate the factors that influence the ability of a QMS to achieve the performance necessary to separate HT ϩ in the presence of D 2 ϩ . Due to the demanding requirements of this application and for the reasons discussed above, the use of circular electrodes was felt to be inadequate for the performance required, and the results achieved in this study are based on a hyperbolic rod QMS.…”

mentioning

confidence: 99%

A Quadrupole mass spectrometer for resolution of low mass isotopes

Sreekumar

J. Am. Soc. Mass Spectrom.

et al. 2010

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The qualitative and quantitative identification of low mass isotopes in the mass range 1-6 u poses certain difficulties when attempting to achieve the required resolution with an instrument suitable for deployment within a process environment. Certain adjacent species present in the process sample (HT and D 2 ) require a resolution greater than 930 to achieve an accurate measurement. We demonstrate here through simulation techniques that this level of performance required is unachievable using commercially available instruments. Using previously reported simulation techniques, this article demonstrates how the required performance for resolving the low mass isotopes can be achieved by a quadrupole mass spectrometer (QMS), which incorporates a quadrupole mass filter (QMF) constructed from hyperbolic electrodes and operated in zone 3 of the Mathieu stability diagram. (J Am Soc Mass Spectrom 2010, 21, 1364 -1370