The assembly under or beside a chamber: high vacuum valve, baffle or trap, high vacuum pump, foreline valve and backing pump. Diffusion pump systems in particular are sold and rebuilt as stacks. Talking about the stack rather than the pump keeps attention on the whole gas path, since a tired stack often has its weak link in a valve or trap rather than in the pump itself.
Pull the whole stack, rebuild the diff pump, clean the baffle and put new O-rings on every valve.
Also heard as
- pump stack
- pumping stack
- pumping train
Related terms
Diffusion pump
High vacuum pump with no moving parts that drives gas toward the exhaust with downward jets of hot oil vapour.
Cold trap
Chilled surface in a pumping line that freezes out water and oil vapour before it reaches the chamber or the pump.
Gate valve
Full-bore valve with a sliding plate that isolates a high vacuum pump or a load lock from the chamber.
Foreline
Pipe that connects the exhaust of a high vacuum or booster pump to its backing pump.
Vacuum symbols
Standard graphic symbols for pumps, gauges, valves and traps used on vacuum system schematics.