A component that passes something through the chamber wall: electrical pins in a ceramic-to-metal or glass-to-metal seal, cooling water tubes, thermocouple wire, optical fibre, or rotary and linear motion through bellows or magnetic couplings. UHV feedthroughs are welded or brazed into CF flanges and must survive the bake-out. Cracked ceramic insulators and pinholes in braze joints make feedthroughs a frequent leak source after thermal cycling.
Leak's at the thermocouple feedthrough, the ceramic cracked when somebody cranked on the connector.
Also heard as
- vacuum feedthrough
- feedthru
Related terms
CF flange
All-metal flange that seals by biting knife edges into a soft copper gasket, the standard joint for UHV.
Bellows
Thin, pleated metal tube that lets a vacuum joint flex or move while staying leak-tight.
Chase a leak
To hunt down a leak of unknown location joint by joint, often over hours, until the source is pinned down.