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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Home brew linear accelerator?
References: <3D8B60B3.1090107@BOGUS.earthlink.net> <3D8C1E99.74B9964D@earthlink.net> <3D8DC36E.516C8809@webaccess.net> <3D8EC823.7A1A0777@Physik.Uni-Muenchen.DE>
Date: Mon, 23 Sep 2002 12:16:41 GMT
NNTP-Posting-Date: Mon, 23 Sep 2002 05:16:41 PDT
Sven Hegewisch wrote:
> Chuck Simmons schrieb:
> > The glass hardly leaks at all. Vacuum tubes made 70 years ago still
> > work. The leaks were due to the epoxy. A good example of this problem is
> > laser tubes. The original epoxy seal tubes had a life of a couple of
> > years whether they were used or not. The hard seal tubes can last for
> > many years. I have some hard seal laser tubes nearly twenty years old
> > that still work.
> > Chuck
> One point to mention is that vacuum tubes have internal pumps - the getter.
> Even if the glass leaks, the vacuum is maintained until the getter is
> used up.
The getter is the last pumping stage in manufacture. It is induction
heated to get it to work. It is inert at normal operating temperature.
The Bevatron accelerator where I once worked had about a dozen 12 inch
or so diffusion pumps in each straight section. These kept the vacuum
good enough for injection energy. At maximum energy, they mattered
little because the mean free path became enormous.
Continuos pumping was needed because the magnet laminations outgassed
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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