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@rubidium.dyndns.org> To: <time-nuts@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@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@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 > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

From: "John Franke" <jmfranke@cox.net> Subject: Re: [time-nuts] Home built Ammonia cell std !! / Home built cesiumclocks??? Date: Sun, 29 Jun 2008 14:02:06 -0400 Message-ID: <004301c8da12$3e04fd40$1e89a662@youre7075dc078> > 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. Sorry, my bad. I suspect wall-pulling is significant. Cheers, Magnus