jimlux wrote:
Hal Murray wrote:
jim...@earthlink.net said:
The gas diffusing out through the drilled bolt.. sure it's drilled,
but the
conductance is so patheticaly low, you're literally waiting until
the gas
molecules happen to randomly bounce their wey up the hole.
I've never worked with vacuum gear.
I assume "drilled bolt" refers to a bolt through a drilled hole so
there is some slop between the bolt and the hole.
No... the bolt has a hole through it, to provide a gas path when you
install it into a blind tapped hole. Otherwise, the trapped gas in the
bottom of the hole slowly leaks out past the threads.
Can I use vacuum grease as a seal around the bolt? Or does it outgas
too much if you are going for seriously low pressures?
For the most part, grease is more trouble than it's worth. Knife edge
seals are where it's at.
Can I use a soft(er) metal washer and mash it to a gas tight fit by
tightening the bolt enough?
Not exactly.. what you see is a knife edge cutting into a softer
metal... "mashing" implies gas trapped between layers.. That kind of
thing crops up in TWT manufacturing, where they stack all the parts of
the gun or the collector...
How low a pressure does a H maser need? Where is it relative to say
fingerprints outgassing?
That's a good question.. I don't know.
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA503712
<http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA503712>
Indicates that the operating pressure at the hydrogen dissociator is
likely to be a few Torr or so.
Bruce
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