Recommended practice for process sampling for partial pressure analysis

Abstract

This Recommended Practice describes and recommends various procedures and types of apparatus for obtaining representative samples of process gases from >10−2Pa (10−4Torr) for partial pressure analysis using a mass spectrometer. The document was prepared by a subcommittee of the Recommended Practices Committee of the American Vacuum Society. The subcommittee was comprised of vacuum users and manufacturers of mass spectrometer partial pressure analyzers who have practical experience in the sampling of process gas atmospheres.

Characterization, optimization and surface physics aspects ofin situplasma mirror cleaning

“…The obvious differences in the plasma chemistry using either oxygen-or hydrogen-based feedstock gas mixtures have become apparent in the present study. Differences start with the different gas kinetics involved in the gas supply system (Blessing et al, 2007) (e.g. due to the different gas viscosities of hydrogen and argon) and also encompass the different reactivity of oxygen versus hydrogen radicals.…”

A new calibration technique for quantitative gas analyses of fluid inclusions using a quadrupole mass spectrometer

“…[1][2][3][4][5][6][7][8][9] The methods from previous studies include thermal decrepitation of fluid inclusions as well as physical crushing to release fluid inclusion volatiles. In these methods, different calibration techniques are employed, such as glass capillaries sealed with high-vacuum epoxy glue, 3 glass capillaries sealed with thermal wire strippers, 4 capillary-introduced laminar gas stream, 2,8 and multi-position switching-style calibration valves. 2,5 There are significant issues with each of these calibration techniques that affect the precision and accuracy of the measurement.…”

“…Capillary tubing and crimps can be used to restrict the amount of gas let into the instrument, but they have a physical lower limit based on the capillary tube diameter and length as well as the pumping capacity of the turbo pump. 2 For some instruments this is still too much gas to measure and/or not equivalent to the amount of gas released from a sample.…”

“…Multi-position switching-style valves 2,5 can be used to introduce a much smaller aliquot of calibration gas, but they are not designed for use under high vacuum and can introduce a background. This calibration method is likely to have the least amount of potential contamination, but significant modifications must be made such as adding capillary tubing between the valve and instrument to avoid overwhelming the ion source and pumping system with too much gas.…”

“…Quadrupole mass spectrometry is an accepted approach for quantitative gas analysis of mineral fluid inclusions in geological samples using a residual gas analyzer with an electron ionization ion source 1–9 . The methods from previous studies include thermal decrepitation of fluid inclusions as well as physical crushing to release fluid inclusion volatiles.…”