[Boatanchors] Smart People: Gassy Tubes Reversable?

[hwhall at compuserve.com]

Yes, that all rings with what I remember from physics classes. So tube's can get gas from outside the envelope as well as from internal outgassing. Which unfortunately still leaves us with the questions of whether there are practical cures. The links provided by VE3BBM and W5JO seem to provide some material for thought & experiment. 

 Wayne
WB4OGM



-----Original Message-----
From: J. Forster <jfor at quikus.com>
To: hwhall <hwhall at compuserve.com>
Cc: arc5 <arc5 at ix.netcom.com>; boatanchors <boatanchors at mailman.qth.net>; milsurplus <milsurplus at mailman.qth.net>
Sent: Tue, Dec 3, 2013 1:19 pm
Subject: Re: [Boatanchors] Smart People:  Gassy Tubes Reversable?

 
 
 
Yes, 
 
Gasses diffuse through glass, even if the metal-glass seals are perfect. 
 
It depends on: 
 
Pressure differential 
Glass permeability 
Gas molecule size. 
 
If you have a glass Dewar and you leave it exposed to He overnight, it'll 
be useless the next day. The He will diffuse through the glass and spoil 
the vacuum. HeNe LASERS die for the same reason. 
 
BTW, gasses diffuse through metals too. Hydrogen diffuses through hot 
Palladium very well. That's how untra-pure H2 is made. 
 
This same physics is use to enrich uranium, as in Iran. 
 
-John 
 
=================== 
 
 
 
 
> > 
> The diffusion rate through a semi-permeable membrane detends on the 
> pressure difference across the membrane. 
> > 
> 
> Hi, John. I think you are referring to gas diffusing through the tube 
> envelope? I hadn't considered that. I was assuming gas "leaking" in or out 
> via wire lead seals, sort of like through nano-cracks between materials. 
> 
> 73, 
> Wayne 
> WB4OGM 
> 
>