[time-nuts] Home built Ammonia cell std !! / Home built cesiumclocks???

John Franke jmfranke at cox.net
Sun Jun 29 14:02:06 EDT 2008


No, I am talking about the 1948 gas absorption design by Lyons, not the 
ammonia MASER.  There is no state-selection.  There is no flowing gas 
molecules.  There is no quadrapole device.  It is a simple oscillator locked 
to the attenuation dip in an absorption cell.  Once built, there is no gas 
replenishment or need for additional pumping.  But, the accuracy is limited. 
By the way, Lyons cell path was 25 feet not 33 feet as I had thought.

John  WA4WDL

----- Original Message ----- 
From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
To: <time-nuts at febo.com>
Sent: Sunday, June 29, 2008 1:26 PM
Subject: Re: [time-nuts] Home built Ammonia cell std !! / Home built 
cesiumclocks???


> From: "John Franke" <jmfranke at cox.net>
> Subject: Re: [time-nuts] Home built Ammonia cell std !! / Home built 
> cesiumclocks???
> Date: Sun, 29 Jun 2008 12:20:28 -0400
> Message-ID: <001e01c8da04$0b83a3c0$1e89a662 at youre7075dc078>
>
>> Now that is something I am interested in doing.  I finally secured use of 
>> a
>> diffusion pump at a local university and expect to be making my first 
>> sealed
>> all-glass absorption cells this fall.  The ammonia pressure needs to be
>> around 8-10 microns.  I will be trying for a double pass cell giving a 
>> pass
>> length between 10 and 12 feet.  The first ammonia atomic clock used a 
>> path
>> length of 33 feet.  The cell was made from waveguide and did not hold a
>> charge due to leaks or the ammonia reacting with the gold plated 
>> waveguide.
>> I believe the best ammonia based standard was only good to 10 ^ -8 in
>> frequency stability.
>
> More like 5E-11 both in cavity pulling and collision effects. Cavity
> pulling was reduced in 1961 by means of automatic cavity tuning.
>
> Recall that you do state-selection on the ammonia beam. An electrostatic
> quadrapole configuration was used. Just like a Hydrogen maser.
>
> Cheers,
> Magnus
>
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