[Amps] Ion Pumps

[Tom W8JI]

> I believe a getter material is used inside vacuum tubes to 
> get rid of
> residual oxygen.

It hopefully gets rid of all gasses, not just oxygen.


 I once overheard someone on the air say that vacuum tubes
> have a vacuum of about 70 Torr (mm of mercury), which is 
> not "high" vacuum.
> But I don't know how accurate that 70 Torr figure is.

Not very accurate at all. As I recall 760 Torr is one 
atmosphere at sea level. 1/10th of an atmosphere is just 
silly. Most tubes would never work.

The pressure inside a vacuum tube is normally in the 10 to 
the -6 or 10 to the -7 Torr range. Generally the vacuum 
pulled is as high as possible but some tubes demand extra 
care.

Tubes are heated and pumped and even have high voltage 
applied, and most smaller tubes have a getter that is 
flashed. It's pretty near a hard vacuum.

73 Tom