[time-nuts] Fwd: Re: homebrew H maser

Robert Darlington rdarlington at gmail.com
Thu Sep 2 00:40:46 UTC 2010


And cryo means ultra high purity helium.  I learned about that the hard
way.  They don't like pumping gravel (solidified trace amounts of oxygen,
argon, etc.)

-Bob

On Wed, Sep 1, 2010 at 5:37 PM, J. Forster <jfor at quik.com> wrote:

> Yup. If you do use oil, you need an LN2 trap.
>
> -John
>
> ===============
>
> > Hi
> >
> > My guess is that you either need a cryo pump or ion pumps and a very good
> > seal.
> >
> > Bob
> >
> >
> >
> > On Sep 1, 2010, at 5:15 PM, Robert Darlington <rdarlington at gmail.com>
> > wrote:
> >
> >> You can pickup oil diffusion pumps pretty inexpensively.   They're not
> >> quite
> >> ion pumps but they get you way down there and they're fast.  With proper
> >> traps you don't really have to worry about coating your experimental
> >> physics
> >> package with oil.  They're cheap to run and easy to maintain.  Ion pumps
> >> are
> >> about as simple as things get and could probably be made very easily by
> >> some
> >> of us "vacuum-nuts" but I never had the need.  Turbo pumps probably
> >> won't do
> >> the job and they're expensive and unforgiving.  Not only did one of mine
> >> crash, it crashed when a sputtering gun melted through.  80,000 RPM
> >> spinning
> >> foil blades don't like hitting the gun cooling water very much!
> >>
> >> Good luck!
> >>
> >> -Bob
> >>
> >> On Wed, Sep 1, 2010 at 2:30 PM, Chris Howard <chris at elfpen.com> wrote:
> >>
> >>>
> >>>
> >>>  Given the quality of vacuum the manual seems to imply, I'm guessing
> >>> this
> >>>> wont cut it.   I'll bet that even low impurity Teflon has a long
> >>>> bakeout
> >>>> period.
> >>>>
> >>>>
> >>> Too bad they don't have some kind of "getter" to allow lower vacuum
> >>> specs.
> >>> I expect they thought of that.
> >>>
> >>> The thing does sound like a giant hydrogenated vacuum tube.
> >>>
> >>>
> >>>
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