AVS 45th International Symposium
    Vacuum Technology Division Monday Sessions
       Session VT-MoM

Paper VT-MoM2
Data Evaluation of Gas-Analytic Mass Spectra: Special Aspects of Getter-Assisted Helium Analysis

Monday, November 2, 1998, 8:40 am, Room 329

Session: Vacuum Gauging, Outgassing and Leak Detection
Presenter: U. Langer, Vienna University of Technology, Austria
Authors: U. Langer, Vienna University of Technology, Austria
R. Dobrozemsky, Vienna University of Technology, Austria
Correspondent: Click to Email
During the last years, a method for the decomposition of complex gas-analytic mass spectra has been developed at Research Center Seibersdorf.@footnote 1@ The method (termed Vector Mass Spectrometry - VMS) is based on the evaluation of data gathered by a quadrupole mass spectrometer (QMS) and a Bayard-Alpert gauge (BAG) during multiple spectrum scans with parameter variation. Although this method allows to analyze even complex mixtures of hydrogen and helium isotopes with accuracies in the percent range, it exhibits severe weakness if small He-amounts have to be measured in a hydrogen background. This particular problem can be overcome by selective pumping, as it has been applied in several labs for similar purposes. In a recent work we have shown that hydrogen reduction factors (i.e. relative He-enrichments) of up to about 50 can be achieved by a simple, orifice controlled SAES getter pump in combination with an additional BAG.@footnote 2@ By a mathematical trick it was possible to evaluate the data by means of the already well-established spectrum decomposition codes, based on a least-squares-fit routine. This method allows quantitative measurements of He-concentrations in the percent range in the presence of hydrogen isotopes. @FootnoteText@ @footnote 1@ R. Dobrozemsky and G.W. Schwarzinger, J. Vac. Sci. Technol. A10(4), 2661 (1992) @footnote 2@ U. Langer and R. Dobrozemsky, contributed paper, submitted to 14@super th@ International Vacuum Congress, Birmingham, UK (1998)