The sum of every source of gas entering a vacuum system, expressed as a throughput in mbar·L/s or Torr·L/s: process flow, real leaks, virtual leaks, outgassing, permeation and backstreaming. Steady-state pressure equals gas load divided by effective pumping speed, so cutting the load is often cheaper than buying a bigger pump. In an unbaked high vacuum chamber, water coming off the walls is usually the largest term.
Gas load from that new polymer fixture is killing us, base went from 1E-7 to 5E-6 the day we installed it.
Also heard as
- load
Related terms
Throughput
How much gas flows past a point each second, counted as pressure times volume, in units such as mbar·L/s.
Outgassing
Slow release of gas from the surfaces and bulk of materials inside a vacuum system.
Permeation
Gas passing through the solid walls or seals of a vacuum system by dissolving into and diffusing through them.
Effective pumping speed
The pumping speed actually delivered at the chamber after losses in the connecting pipes and valves.
Virtual leak
Gas trapped in a hidden pocket inside the vacuum that bleeds out slowly and behaves like a small real leak.