On Thu, 10 Nov 2016 11:20:37 +1100 Jim Palfreyman <[email protected]> wrote:
> Anyone got any comments on this? > > http://www.theleadsouthaustralia.com.au/industries/technology/worlds-most-precise-clock-set-for-commercial-countdown/ Cryogenic sapphire or whispering gallery mode oscillators have been around for quite some time. You basically have a piece of sapphire (aluminium oxide in crystaline form)[1] in a cavity[2,3], cool everything down to liquid helium temperatures and use this as an oscillator. There are two popular configurations, one is to use the sapphire as resonant element like in an LC or crystal oscillator, or more commonly, to use the sapphire as a filter element in Pound locking scheme[4]. The short term stability of these oscillators is AFAIK unsurpassed and flat up to 1000-10'000s, but exhibits drift at longer taus[5]. Their biggest problem is that they need a liquid helium cryo-cooler which causes vibrations that need to be carefully filtered out. This also makes them relatively large (fill between one and two 19" racks) Attila Kinali [1] http://www.uliss-st.com/uploads/pics/tech2.jpg [2] http://inspirehep.net/record/1244235/files/cavity.png [3] http://www.uliss-st.com/uploads/media/imgmedias.jpg [4] That's the (original) microwave variant of the Pound-Drever-Hall locking scheme, see https://en.wikipedia.org/wiki/Pound%E2%80%93Drever%E2%80%93Hall_technique [5] http://inspirehep.net/record/1409150/plots -- Malek's Law: Any simple idea will be worded in the most complicated way. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
