[R-390] TUBES

[Gregory W. Moore]

Let us not forget the plethora of helium mass spectrometers which have
been floating around for years. The primary use, at least the one I have
most experience dealing with, is leak testing aircraft instruments,
which after being hermetically sealed, are baked in a vacuum,allowed to
be filled with dry N2, evacuated again baked again,  then backfilled
with a 90%N2 10%He mix and the evacuate and fill port sealed. Since the
spectrometer (Which was set to measure He only, to find out if the
instrument was leaking,)  could only operate at a hard vacuum, they were
equipped with a roughing pump which took out most of the air in the bell
jar placed over the sealed instrument, a fore pump, which removed just
about all that was left, and a diffusion pump to take the whole shebang
just about down to nothing. Any minor presence of air in the mass
spectrometer tube would render it inoperable. They also had a "cold
trap" which either used a criogenic pump, or LN2 to remove all moisture
in the circuit. The criogenic cooling pump didn't work all that well,
and it became a daily event to fill the trap with LN2, and refilling it
throughout the day as it evaporated.  Working overtime on weekends, one
could have a lot of fun with the LN2 and the effects of the criogenic
temps on different materials (rubber balls, for example, Hockey pucks
made out of GE molding compound, then frozen, or making hammers out of
mercury (can you even picture trying that little stunt today??)...
Somehow, I feel there has got to be a lot of these units, with  bad
circuitry, bad spectrometer tubes, or just plain age, waiting for use
after some rather easy modification to use them to evacuate glass
envelopes to a high enough vacuum.
It seems to me that if one has to fix something bad enough, then one
comes up with a viable solution using (hopefully) stuff considered
obsolete and therefore, cheap (Important to most of us hams, who,
traditionally, don't have much money)
Greg

Richard Loken wrote:

> On Thu, 14 Feb 2002, Joe Foley wrote:
>
> > Bausch and Lomb in Rochester, NY could have done this
> > but they gave away all of the vacuum chambers we built
> > for them and canned all of the people who knew how to
> > do all of that stuff.
>
> > CVC high vacumm products is in Rochester, too, they
> > know all about this stuff.
> >
> > This wouldn't be that tough to do, like everything
> > else it would take MONEY!  Lots of MONEY!!
>
> Oh it doesn't have to cost that much if you can find a surplus
> electron microscope.
> ---
>    Richard Loken VE6BSV, Systems Programmer - VMS
>    Athabasca University
>    Athabasca, Alberta Canada
>    ** richardlo@admin.athabascau.ca **
>
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