[time-nuts] Frequency processing scheme of HP5065vapourrubidium standard

[Normand Martel]

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
> 
> 
> 
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