| AVS 63rd International Symposium & Exhibition | |
| Vacuum Technology | Tuesday Sessions |
| Session VT-TuM |
| Session: | Vacuum Pumping and Material Outgassing |
| Presenter: | Janez Setina, Institute of Metals and Technology (IMT), Slovenia |
| Authors: | J. Setina, Institute of Metals and Technology (IMT), Slovenia K. Jousten, Physikalisch-Technische Bundesanstalt (PTB), Germany |
| Correspondent: | Click to Email |
Water vapor is usually main constituent of residual gas in non-baked high vacuum systems. The principal source of water vapor is outgassing from surfaces of vacuum chamber. Significant amount of water vapor is adsorbed on the surfaces every time when the system is vented to moist ambient air. Outgassing rate of water vapor is therefore important parameter of any vacuum material and is needed for proper design of the system to operate in required pressure range.
Traceability of outgassing rate measurements was one of the research activities of the recently finished European project EMRP IND12. For calibration, validation and comparisons of outgassing rate measurement systems different reference outgassing samples were studied. In this presentation we will focus on the reference samples for water vapor outgassing, which were jointly developed and applied for patent by PTB and IMT [1]. For measurement and calibration of outgassing rate from reference samples for different gases, including water vapor, a dedicated vacuum system was developed at IMT. Measurement range of the system for water vapor outgassing rate at room temperature is from 5×10-7 mbarL/s to 5×10-3 mbarL/s (equivalent to 2×10-11 mol/s to 2×10-7 mol/s, or 3×10-5 g/day to 0.3g/day). Typical relative uncertainty of measured outgassing rate is below 5 %.
Results of calibration of two water vapor reference samples will be presented. One sample had nominal outgassing rate of water vapor 6×10-7 mbarL/s (2.5×10-11 mol/s, or 4×10-5 g/day) and another sample 3×10-5 mbarL/s (1.3×10-9 mol/s, or 2×10-3 g/day). Both samples represent constant outgassing rate over long period of time. Repeated measurements showed time stability of reference samples better than 3%/year.
The newly developed water vapor outgassing reference samples can be also used for calibration of measurement instruments for water vapor transfer rate (WVTR).
[1] Patent DE 102014200907 A1 (2015)