| AVS 59th Annual International Symposium and Exhibition | |
| Vacuum Technology | Monday Sessions |
| Session VT-MoA |
| Session: | Gas Flow, Leaks, Permeation and Mass Analysis |
| Presenter: | R. Ellefson, REVac Consulting |
| Authors: | K. Jousten, Physikalisch Technische Bundesanstalt, Germany J. Šetina, Institute of Metals and Technology, Slovenia R. Ellefson, REVac Consulting |
| Correspondent: | Click to Email |
The ISO Technical Committee (TC) 112 is responsible for international standards in the field of vacuum technology. Supporting TC112 are three working groups (WG): WG1 is responsible for vacuum pumps, WG 2 for vacuum instrumentation and WG 3 for vacuum hardware. Hence, the WG 2 is responsible for total and partial pressure measurement in vacuum. In 2006, WG 2 began a project towards standardization for the specification and calibration of quadrupole mass spectrometers (QMS). A new ISO (Draft) standard 14291 “Definitions and specifications for quadrupole mass spectrometers” will be published in 2012. Additionally WG 2 is working on documenting the proper use of a QMS and establish a standard for meaningful calibration procedures. In support of this ISO goal, the European Metrology Research Programme has established a project IND12 “Vacuum metrology for production environments” to open new measurement capabilities for vacuum and to help industry to characterize vacuum in industrial environments.
One of the focuses of this IND12 effort is to address traceability to national measurement standards for partial pressure measurements and outgassing rate measurements for materials characterization in industry. To gather current status on such methods, a workshop on calibration of the QMS for industrial use was held in Bled, Slovenia. Quadrupole mass spectrometers are widely used to measure partial pressures in vacuum although the performance and accuracy of these measurements is the subject of ongoing discussion among users. The wide range of partial pressure measurement needed from UHV/XHV (10-10 Pa) to 1 Pa emphasizes that one type of QMS does not address all applications. From presentations at this workshop, application-specific data on performance of QMS types gives guidance for selection of a QMS type for an application. Talks were given on setup and ion source operation recommendations; initial calibration methods for an application and in situ calibration methods for verification or recalibration of a QMS during use. The fact that QMS electron energies differ by application and manufacturer leads to the requirement that gas species calibration is needed for each QMS for accurate partial pressure or compositional analysis. Papers on the electron-ion space charge at pressures>10-4 Pa in ion sources were given together with gas interference where addition of a partial pressure of a new chemical species B gives a different ion current output for species A (when A is known to be at its original partial pressure). Results of these talks at the workshop will be summarized in this presentation.