[time-nuts] homebrew maser

[J. Forster]

Microwave test gear and plumbing is very significantly harder to get at 24
GHz than at 1.4 GHz.

At a guess I've seen easily 100 times more stuff available at 1.4 GHz.

FWIW,

-John

============



> That's a great article.  It almost makes the job seem doable.
>
> It is going to be expensive, though.  If someone can build a working maser
> for less than $10K in materials and bespoke fabrication services alone,
> I'll
> be impressed.  An obvious question is, what's the so-called "minimum
> viable
> product" that can actually produce a population inversion in a cavity and
> demonstrate maser action?  Do you need any magnetic shielding at all,
> beyond
> a couple of Helmholtz coils?  Maybe not.  Do you need to coat the bulb at
> all if you don't care about line width?  Maybe not.  How exotic does the
> collimator need to be if you don't care much about service life?  Probably
> not very.  You definitely don't need a multilayer vacuum system.  What
> corners can be cut to get a rough prototype running?
>
> Control electronics is trivial, and not even worth thinking about until
> the
> physical details are nailed down.
>
> Once you start talking about cutting corners just to get a maser up and
> running, though, there's another obvious question worth considering: what
> about starting with an ammonia maser?  This was the first molecular
> oscillator.  Experience optimizing the (numerous) operating parameters in
> an
> NH3 maser would no doubt be helpful in later work with an H maser.
>
> Ammonia molecules have a dipole moment and can be state-selected
> electrostatically.  There is no need for either a dissociator or a storage
> bulb, just a basic electrostatic lens and cavity in a vacuum.  Townes's
> original 1954 paper makes no mention of magnetic shielding.  But at 24 GHz
> a
> high-Q cavity is small and manageable, so if you do have to enclose it in
> mu-metal it's not going to cost a fortune.
>
> Further, with stabilities in the 1E-12 range, a 5065A-class rubidium
> standard or a well-optimized GPS clock can be used as a reference for
> tweaking and debugging an NH3 maser.  If you do manage to build a hydrogen
> maser, OTOH, you are going to need to build at least two of them to get
> any
> idea where your performance floor is.
>
> Just one possible thought...
>
> -- john, KE5FX
>
>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of Bruce Griffiths
>> Sent: Tuesday, August 31, 2010 1:23 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] homebrew maser
>>
>>
>> PTFE wall storage bulb wall coatings haven't been used for some decades,
>> FEP (or the Russian fluoropolymer ) is better in that a smoother coat is
>> achievable see:
>> http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&
>> AD=ADA509340
>> <http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf
>> &AD=ADA509340>
>>
>> A sual hexapole state selector is probably a little more effective than
>> the cruder method used in the Russian masers.
>>
>> Bruce
>>
>> Mark Sims wrote:
>> > Same general idea,  but an image intensifier plate would
>> probably not work well.  They are usually thinner and are cut at
>> a bias so the electrons ricochet along its length.  You might be
>> able to mount one so that it cancels the bias angle.
>> >
>> > They are made by stretching a bundle of hollow glass tubes that
>> have been filled with solid glass rods of a different
>> composition.  The original bundle can be very large (like over a
>> meter) and is shrunk down to like 100 fibers per millimeter.  It
>> is then sliced and polished.  Often the slices (or the pulled
>> bundles) are joined into a bigger plate.   Then the inner solid
>> glass is dissolved out with a strong alkali. The hollow tubes are
>> coated with a photoelectric material.
>> > The image from the tube is inverted using a "twister"...  a
>> coherent fiber optic rod that has a 180 degree twist.
>> >
>> > ---------------
>> > Do you know if the collimator is made from an uncoated
>> microchannel plate?
>> > If so, an old, broken Gen II image intensifier might be a viable
>> source.
>> >
>> >
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>>
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