To admit a specific gas, typically nitrogen, argon or helium, into a pumped chamber, either to vent it cleanly or to set a working atmosphere. Vacuum furnaces backfill with argon or nitrogen for cooling and gas quenching, and package sealing backfills to a set pressure before the lid goes on. Pumping and backfilling several times in a row, a cycle purge, strips moisture and oxygen far faster than pumping alone.
Backfill with argon to 600 torr, then start the fan for the quench.
Also heard as
- back-fill
- backfilling
Related terms
Vent
To let gas back into an evacuated chamber, usually dry nitrogen, to bring it up to atmosphere.
Convection gauge
Pirani-type gauge that uses gas convection around the heated wire to read from about 10⁻³ mbar up to atmosphere.
Bleed
To admit a small, controlled flow of gas into a vacuum system through a needle or leak valve.