[time-nuts] homebrew H maser

[Attila Kinali]

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