VSE knjižnice (vzajemna bibliografsko-kataložna baza podatkov COBIB.SI)
  • Calibration of quadrupole mass spectrometers for gas quantity and gas flow measurements [Elektronski vir]
    Šetina, Janez ; Erjavec, Bojan, 1950-2023
    Total pressure in a vacuum system is a sum of partial pressures of different gases. The composition depends on the conditions of the vacuum system (background) and on the gases released from the ... "vacuum process". Quite often it is important to know and control not only the total pressure, but also the composition. Different gases can have different influence on the process (for instance oxidative, reductive or inert environment). For composition analysis Quadrupole Mass Spectrometer (QMS) are most widely used. The use of QMS extends from simple qualitative analysis which gases are present (for instance presence of nitrogen, oxygen and argon from atmosphere indicates a leak), to quantitative analysis of the abundance of individual gases. A response (sensitivity) of the QMS for different gases depends on many factors, starting from ionization efficiency, ion extraction from ionizer and focusing into a quadrupole filter, to ion transmission and finally ion detection efficiency. All these factors are very sensitive to the settings of QMS parameters like cathode potential, extraction and focusing voltages, and especially on resolution setting (RF to DC ratio and DC offset) of quadrupole filter. In the talk the influence of QMS settings on the sensitivity will be discussed. Any adjustment of the settings requires recalibration of the instrument to get correct sensitivity coefficients for different gases. Periodical recalibration is also necessary due to the inevitable temporal instability or drift of the instrument's electronics. In principle QMS can be calibrated as any other ionization vacuum gauge on a primary vacuum calibration system at national metrology lab or in a secondary calibration facility. However such calibrations are often limited to nitrogen and argon gas. Alternatively QMS can be also calibrated in-situ in the vacuum process system. This may be preferable when the QMS has to be calibrated as often as necessary or when it is not desirable to dismount the QMS from the vacuum system for calibration. In the talk we will focus on in-situ calibration procedures taking into account also characteristics of the vacuum system like effective pumping speed for different gases at the location of QMS, which enables direct calibration of the QMS for gas quantity and gas flow measurements.
    Vir: 18th International Vacuum Congress (IVC-18) [also] International Conference on Nanoscience and Technology (ICN+T 2010) [also] 14th International Conference on Solid Surfaces (ICSS-14) [also] Vacuum and Surface Sciences Conference of Asia and Australia (VASSCAA-5), August 23-27, 2010, Beijing, China [Elektronski vir] : abstract CD (1 str.)
    Vrsta gradiva - prispevek na konferenci
    Leto - 2010
    Jezik - angleški
    COBISS.SI-ID - 853418

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