Date: Sun, 2 Dec 2007 11:36:48 -0800
From: btmeehan@xxxxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Large Plsma Tube
CC:
Where do you guys get the big globes from? (or even medium or small sized
globes) Do you have to have a glass-blowing setup in order to really play
with these things or do you just order pyrex chemistry glassware?
On Dec 1, 2007 7:35 AM, Bill Lemieux <gomezaddams@xxxxxxxxx> wrote:
PS: I forgot to mention the end-seals. Because the ends will probably
have to be flat, you should consider using 1/2" thick plate to span a
6" distance. This is a bit on the overkill side for 15PSI of
pressure, but better safe than sorry! Make sure you don't introduce
any small cracks when you drill the plates for your electrodes, and
polish all edges to eliminate sharp edges or pits from drilling or
cutting. Use fine emery paper for this.
Forget about using plastics for your end plates, it won't last. Among
other things, atmospheric helium and hydrogen will leak in (through
the material) over the passing years... possibly changing the
appearance of your discharge significantly. You're going to have
problems with that using epoxy seals anyway, but if the exposed area
of the epoxy seal is tiny and the thickness great (ie; .25") they
ought to be good for many years.
The higher pressure you can operate at, (approaching atmospheric) the
slower this leak problem will be.
This is why old epoxy-sealed HeNe lasers died after about ten years -
the helium would diffuse out through the seals. Amazingly, because
there was still a low pressure inside the tube, you could rejuvenate
those old tubes by sticking them in a bag of cheap balloon helium, and
operating the tube - you'd check it every few days and eventually it
would be working as good as new. Take it out of the bag, and it would
once again be good for years. Of course, with modern diode lasers and
even cheap hard-seall HeN lasers being so plentiful, that isn't worth
the effort. Epoxy-sealed HeNe lasers are worthless now.
- "Gomez"
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