Describes a system whose surfaces are loaded with water, usually after a long vent, a humid day or a clean with water-based solutions. A wet chamber drops quickly at first, then crawls in the 10⁻⁵ to 10⁻⁶ mbar range while an RGA shows mass 18 dominating. The fixes are a bake or a longer pump, and next time a dry nitrogen vent and a shorter door-open time.
Chamber was open all weekend, it's wet, we won't see E-7 until tomorrow morning.
Also heard as
- wet chamber
- water-loaded
Related terms
Outgassing
Slow release of gas from the surfaces and bulk of materials inside a vacuum system.
Bake-out
Heating a vacuum system while pumping to drive off water and other adsorbed gas and lower the base pressure.
Vent
To let gas back into an evacuated chamber, usually dry nitrogen, to bring it up to atmosphere.
RGA
Residual gas analyzer: a small mass spectrometer that identifies which gases remain in a vacuum chamber.
Pump-down curve
Plot of chamber pressure against time during a pump-down, used as the fingerprint of a healthy system.