The pressure one gas in a mixture would exert if it filled the volume alone; the partial pressures of all species add up to the total. In vacuum work it often matters more than the total, since a process can tolerate 10⁻⁶ mbar of argon but not 10⁻⁸ mbar of water or oxygen. Partial pressures are measured with a residual gas analyzer, because an ionization gauge only gives a gas-weighted total.
Total's fine at 3E-7 but the water partial pressure is half of that, give it another bake.
Also heard as
- partial
Related terms
RGA
Residual gas analyzer: a small mass spectrometer that identifies which gases remain in a vacuum chamber.
Base pressure
The lowest pressure a particular chamber reaches after pumping for a set time with no process gas flowing.
Outgassing
Slow release of gas from the surfaces and bulk of materials inside a vacuum system.