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From: Sven Hegewisch
Subject: Re: Home brew linear accelerator?
Date: Tue, 24 Sep 2002 11:43:47 +0200
Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany)
References: <3D8B60B3.1090107@BOGUS.earthlink.net> <3D8C1E99.74B9964D@earthlink.net> <3D8DC36E.516C8809@webaccess.net> <3D8EC823.7A1A0777@Physik.Uni-Muenchen.DE>
NNTP-Posting-Date: 24 Sep 2002 09:43:53 GMT
X-Mailer: Mozilla 4.7 [de] (WinNT; I)
George Gonzalez schrieb:
> Just a minor point, but
> I don't think this is quite right.
Yes and no. See below.
> The way I've heard it,
> the getter is heated during manufacturing,
> and the hot metal absorbs most of the remaining gases.
> Once cool, the getter has a very limited ability to absorb gas.
1.) The getter material is Barium. It works best when the
surface is large.
2.) The material in the getter pill is
Bariumoxide plus Aluminium. By heating pure Barium and
Aluminiomoxide is produced.
3.) In the production of tubes the getter pill is induction heated
and the barium film condenses on the inner tube surface
while the vacuum pump still pumps. Now the tube will be closed.
By this action the outgassing of the getter pill is removed by
the vacuum pump and an active pumping film is left.
> The best examples of this are the many type 201A tubes still around,
> most working just fine after 70+ years, with getters still shiny and
Yes - there also exist counter examples. Some series of tubes for the
last stage of audio amplifiers foe example. They worked until the Barium
film was transparent. Then they got a bluish 'glow' an died soon afterwards.
There also exist tubes where the anode material works as getter.
The are mostly high power RF tubes.
The active pumping with barium getters is used also in high vacuum
solar collectors. The producers explictily mention this fact.
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