> 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 [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
