From: John Woodgate
Subject: Re: Home brew linear accelerator?
Date: Wed, 25 Sep 2002 12:19:51 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Wed, 25 Sep 2002 13:47:50 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Robert Baer
wrote (in <3D915EB6.303861B0@earthlink.net>)
about 'Home brew linear accelerator?', on Wed, 25 Sep 2002:
All right, but be quick, and don't forget to wash your hands.
> the getter system worked only *once*, after the
>manufacturer pulled a vacuum and sealed the tube, then the getter was RF
>activated ("flashed"), evaporating some of the surface material.
> That created an ionizes metal vapor which reacted with any oxygen and
>adsorbed other gasses; the vapor depsoited on the inside of the glass,
>making a silvery deposit.
The getter does continue to work in service; remember that the operating
temperature is considerably above room temperature. It doesn't work very
well at room temperature, so an old tube may show high grid current when
first re-heated, but less later as the gases are cleaned up.
> If that deposit ever showed oxidation, then one knew for a fact the
>tube was gassey and useless.
Yes, if you can see a white deposit, that's final. You don't see any
significant change (maybe slight dulling of the surface exposed to
vacuum) while the getter is just cleaning up traces of gas.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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