[time-nuts] homebrew H maser

Mark Kahrs mark.kahrs at gmail.com
Sun Aug 29 20:26:05 UTC 2010


The Hahvahd physics dept. has all number of interesting papers.

For example there's Humphrey's
dissertation:www.physics.harvard.edu/Thesespdfs/humphrey.pdf

If you've ever wanted to make your own Rb cell, how about this
one?cfa-www.harvard.edu/~dphil/work/coat.pdf
<http://cfa-www.harvard.edu/%7Edphil/work/coat.pdf%20>


On Sun, Aug 29, 2010 at 11:07 AM, Attila Kinali <attila at kinali.ch> wrote:

> On Sun, 29 Aug 2010 16:13:21 +0200
> Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>
> > On 08/29/2010 03:55 PM, Attila Kinali wrote:
> > > Does anyone know whether any of those people collected their results
> > > somewhere? And if, where i could find them?
> >
> > The physical package is definitely where most of the effort goes in.
>
> I know, that's why i'm asking.
> The papers i've read sofar all suggest that the difficult part is to
> compensate for cavity detuning, wall shift and second order doppler
> effect. Somehow all these papers seem to assume that getting an
> oscillation at all is so easy that everyone could do it (yes, i know that
> this is normal with scientific papers).
>
> I thought, that if someone build a homebrew H maser, he'd write about
> the difficulties getting there. Which would be a very interesting reading
> and teach a lot about the physics (and tool making, mechanics, etc)
> of these devices.
>
> > A
> > complicating aspect is the self-tuning stuff for which several
> > strategies may be chosen.
>
> I'd start here at getting a cavity that is resonant at the frequency
> at all. Getting sub-milimeter precision in tooling is quite easy
> (given you have the tools and knowledge, or can pay someone to do it for
> you),
> but if the cavity has to be resonant within a couple of Hz of the
> 1.4xxxGHz, then you have to get a precission in the range of 10^-9
> which basically impossible mechanically. So the cavity would need to have
> a mechanical tuning system too, but one that doesn't lower the cavity's
> Q or add any additional resonant modes.
>
> > You need to balance the rate of the atoms, as both too few and too many
> > kills the oscillation.
>
> Or get to the basic requirement of getting a pure H2 source to feed
> the beam source. The beam source itself, including the dissociator,
> would be a formidable project to do at home by itself.
>
> > The size of the glass-bulb is not a fixed thing, during research and
> > development different sizes glass-bulbs is used to establish the
> > wall-shift aspects in order to adjust for it, which is needed in order
> > to make absolute measurements on the "free" atom resonance or compensate
> > into that regard.
>
> Interestingly, i think that the bulb would be the easiest part
> these days. At least around here, there are a few glas blowers
> for the chemical/pharmaceutical industry that also do single pieces.
> Getting it coated would only involve finding a company that does
> teflon coating (there do seem enough of them). From what i gather
> it's shape doesnt have to be exactly spherical down to the
> sub-milimeter range.
>
> > As for reference, there is about one set of books and papers from a
> > handful of journals and a bunch of patents which needs to the read in
> > order to build up the knowledge-base for attempting something like it.
>
> Which papers/books would you recommend reading?
>
> And no, i don't think i'd attempt to build a H maser.
> I'm quite confident i could do the electronics part, but i know that
> i don't know anything when it comes to mechanics. Much less about
> handling high vacuum and atomic gas beams.
>
> > It's a complicated field and several traps to fall into on the way. It
> > is a fairly sizeable project to attempt.
>
> Yes, but it's fun to read about it :-)
>
>                        Attila Kinali
>
> --
> The trouble with you, Shev, is you don't say anything until you've saved
> up a whole truckload of damned heavy brick arguments and then you dump
> them all out and never look at the bleeding body mangled beneath the heap
>                -- Tirin, The Dispossessed, U. Le Guin
>
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