"Jeff Liebermann"

When we talk about a "gassy" vacuum tube, it's not a leaky glass
envelope or seal.

** The term covers that eventuality too.

Any tube that has even a tiny air leak will glow a pinkish purple inside
like a *******.


The getter does best with reactive gases and does
nothing for eliminating noble gases, which will not react with metals
(or most anything else). It's those noble gases that remain (helium,
neon, argon, krypton, xenon, and radon) that you're seeing glow.


** Maybe - but how would any significant amount of Argon get inside the
tube UNLESS there was air leaking in ?

Remember, Argon makes up less than 1% of air and does not react with metal
parts.

The vacuum inside a tube is less than one millionth of atmospheric pressure.

BTW:

Nitrogen mixed with a little CO2 makes a nice, white glow under low
pressure - its called a "Moore Tube"

http://en.wikipedia.org/wiki/Daniel_McFarlan_Moore

His untimely death was a bit shocking.


..... Phil