[time-nuts] homebrew H maser

J. Forster jfor at quik.com
Sun Aug 29 17:03:02 UTC 2010

>> 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.

A tuning plunger driven with a Burleigh Inchworm, either through a bellows
or with a vacuum Inchworm.

>> You need to balance the rate of the atoms, as both too few and too many
>> kills the oscillation.

There are commercial adjustable leaks and Mass Flow Controllers by MKS for

> 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.

Kimball Physics sells parts for doing this.

>> 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.

The pumping is pretty straight forward. You would likely need a source of
LN2, at least for a while. The vacuum needs to be clean, which means
traps. Sorbtion & ion or Ti sub pumps would be a better idea.

>> 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




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