>The "experimental" clocks based on lonely ions and quantum embraces are very likely primary, once somebody has measured their intrinsic frequency relative to Cs once.
No they cannot be - yet. At the point where (e.g.) the second is re-defined in terms of the aluminium quantum clock, then the aluminium quantum clocks are then by definition the primary standards of time, and all the Cs clocks are now secondary standards as the second is no longer defined in terms of the Cs beam clock. Dave -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: 23 February 2010 22:49 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Primary Standards... In message <20100223214204.eae71117...@hamburg.alientech.net>, Mike S writes: >renamed, since the discussion has shifted. >"In the time and frequency field, the term primary standard is >sometimes used to refer to any cesium oscillator, [...] That rhymes with and Karls and my perception of the term: A Cs clock is primary because when you turn it on, it latches onto the physical phenomenon of a known and invariant frequency subject to no systematic errors. The reason the small Rb's do not qualify as primary is that each unit has a slightly different frequency, due to vapour pressure, isotopemix and other physical details, and thus you cannot know the frequency of a particular unit, until you have measured it relative a primary clock. In other words, Primary and Secondary has nothing to do with which atoms, but depends a lot on the interogations mechanism used. So the tiny 1cm^3 Cs standards are secondary, because they are also subject to all sorts of pulls and offsets. The "experimental" clocks based on lonely ions and quantum embraces are very likely primary, once somebody has measured their intrinsic frequency relative to Cs once. The way to find out if your new invention has a chance to become a primary clock, is to build N of them, turn them on, and see if they all find the same frequency once they are locked, if they do, you're on your way to become famous. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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. _______________________________________________ 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.