[time-nuts] Frequency processing scheme of HP5065vapourrubidiumstandard

Rob Kimberley time.bandit at btinternet.com
Wed Nov 8 06:45:59 EST 2006


Please see the link below - gives quite a good explanation of laser cooling.
There are more detailed texts available at NIST in the US and NPL in the UK.

 http://en.wikipedia.org/wiki/Laser_cooling

Rob K

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Normand Martel
Sent: 08 November 2006 01:25
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Frequency processing scheme of
HP5065vapourrubidiumstandard

Thanks! very interesting articles!!!

But something bugs me... In both fountains and single ion mercury standards,
lasers are used to COOL DOWN atoms...

How is it possible? Lasers are energy sources, and (at least for me),
anything that is hit by a laser will get warm, not cold!

Thanks for your attention..

Normand Matrel

--- Tom Van Baak <tvb at leapsecond.com> wrote:

> > Seems very interesing!!!
> > 
> > If i'm right, That could lead to rubidium based primary standards...
> > 
> > Normand Martel
> 
> Hi Normand,
> 
> There are many factors which pull cesium too; and if you want to get 
> technical the actual frequency inside a typical cesium standard, even 
> at sea-level, isn't exactly
> 9 192 631 770 Hz anyway.
> 
> To see a very detailed list of pulling and corrections of a cesium 
> standard read something like this:
> 
> Accuracy evaluation of the primary frequency standard NIST- 
> http://www.tf.nist.gov/timefreq/general/pdf/1497.pdf
> 
> I think you will be very surprised as how complicated it really is to 
> make a good frequency standard. See also this vintage, but more 
> readable, less technical
> description:
> 
> HP 5062C Cesium Beam Frequency Reference, Theory of Operation 
> http://www.leapsecond.com/museum/hp5062c/theory.htm
> 
> Finally, if you'd like to read about current developments in rubidium 
> fountains, a good example is found here:
> 
> The USNO Rubidium Fountain Project
>
http://tycho.usno.navy.mil/clockdev/RubidiumFountain.html
> 
> For technical details google for rubidium fountain.
> 
> Still, optical clocks are the ones likely to succeed cesium in the 
> coming decade. It seems several times a year there are new 
> breakthroughs with optical clocks. For
> example:
> 
> Mercury Atomic Clock Keeps Time with Record Accuracy
>
http://www.nist.gov/public_affairs/releases/mercury_atomic_clock.htm
> 
> /tvb
> 
> Let me also repeat this posting from last week:
> 
> > To answer your good question; we all have come to know that cesium 
> > is accurate and rubidium drifts.
> But
> > there's much more to the story...
> > 
> > There are different ways to partition the world of
> atomic
> > clocks. One is by atom: we have Cesium, Rubidium, Hydrogen, Mercury, 
> > and several others.
> > 
> > The other is by technique. We have masers, thermal beams, optical 
> > pumping, fountains, and several
> others.
> > 
> > The existence of drift in an atomic clock is a
> function
> > of the technique rather than the atom.
> > 
> > So, yes, all commercial Rb clocks drift, but not
> really
> > because they use rubidium. A Rb beam clock (if one
> > existed) would, like a Cs beam, not drift.
> > 
> > Similarly, a rubidium fountain is just as
> driftless as a
> > cesium fountain (in fact, a rubidium fountain may
> well
> > outperform a Cs fountain).
> > 
> > One clue is that you hear the phrase "rubidium
> vapor
> > frequency standard" (e.g., hp 5065A) as opposed to the phrase 
> > "cesium beam frequency standard" (e.g., hp 5061A). The physics is 
> > completely different.
> > 
> > To read more about why all commercial, compact, low-cost, low-power 
> > rubidium standards have drift google for words like rubidium buffer 
> > gas.
> > 
> > For a quick overview of Cs and Rb standards see:
> >
>
http://tf.nist.gov/general/enc-re.htm#rubidiumoscillator
> > http://tf.nist.gov/general/enc-c.htm#cesiumbeam
> > http://tf.nist.gov/general/enc-h.htm#hydrogenmaser
> 
> 
> 
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
>
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> 




 
____________________________________________________________________________
________
Yahoo! Music Unlimited
Access over 1 million songs.
http://music.yahoo.com/unlimited

_______________________________________________
time-nuts mailing list
time-nuts at febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts





More information about the time-nuts mailing list