[time-nuts] Homebrew H Maser

Attila Kinali attila at kinali.ch
Tue Aug 31 16:32:58 UTC 2010

On Sun, 29 Aug 2010 13:27:13 -0700
Corby Dawson <cdelect at juno.com> wrote:

> -The triple magnetic shields are VERY important. The first time I removed
> the top
>  shield to access the RF section the Maser stopped oscillating! Replacing
> the shield
> restored oscillations!

Hmm.. i'd guess that the oscillation went outside the cavity's resonant
range. Other than shifting the resonance frequency and spreading the
hyperfine lines, it should not have any other effect. But i might
be very well wrong.

> -The cavity does not have to be machined to "super precise levels", in
> this Maser once the coarse setting (mechanical at factory) is made, the
> medium tuning is done by adjusting the cavity temperature. The fine is
> done with the cavity varactor. This cavity is aluminum.

The thermal length constant of Al is 23e-6/K, which means that per
°C you get a pulling of about 23ppm of the frequency. Guestimating
that more than 20°C of heating should not be done to keep the whole
thing in a easy to handle range. Then we would have a maximum pulling
range of +/-230ppm, which means +/-10um precission on a 10cm diameter.
This is still a very thight tollerance. Not impossible, but not that
easy either.

> -Making a homebrew collimator (at the discharge bulb output) might be
> hard, google it and you will see it's  tricky.

I couldn't find anything telling me that it is difficult to do
when i did a quick search. If i understood it correctly, the collimator
for a H-maser is nothing else than a tight and straight pipe from the
H beam source to the state selector magnet. Did i misunderstand something

> I have, somewhere, a scan of the two manuals. There is lots of theory and
> full schematics. Might be a good read if you are serious in trying to
> homebrew one.
> I'll dig them up and see if anyone could host them on a website. (Files
> are quite large!)

I would very much like to read those. Even if i dont build a maser.
As John suggested, it would be IMHO best to put them on Didier's site
as others might be interested as well. 

			Attila Kinali
If you want to walk fast, walk alone.
If you want to walk far, walk together.
		-- African proverb

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