The idea of a Mercury Ion clocks started about 2000 and from about 2005 until recently has held the title of worlds most accurate clock. Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single trapped mercury atom. Jim Bergquist at NIST was one of those that lead the development. This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want two.
Thomas Knox 1-303-554-0307 > Date: Sun, 5 May 2013 06:59:12 -0700 > From: jim...@earthlink.net > To: time-nuts@febo.com > Subject: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs > > On 5/5/13 1:48 AM, Magnus Danielson wrote: > > On 05/05/2013 10:05 AM, Attila Kinali wrote: > >> On Sat, 4 May 2013 12:36:20 -0700 > >> "Tom Van Baak (lab)"<t...@leapsecond.com> wrote: > >> > >>> Rule of thumb: quartz is best short term, Rb or H-maser mid-term, > >>> and Cs by far the best long-term. > >> > >> Ah.. so it's a fundamental limitation. And i was looking for something > >> GPS specific. > >> > >> Any references i could read on those limitations? A quick google > >> did not produce any good results. > > > > There is a handful of references but picking up a book like "Quantum > > Leap" is a good start. > > > > Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, > > mounted in some hermetic sealed chamber with residue dirt, and mounting > > <snip> > > > > > For rubidium gas-cell, there is a bunch of systematics, including > <snip> > > > The caesium atomic beam does not have wall-shifts, but rather it has > > much lower systematics. One of the major onces being magnetic field. > <snip> > > > The above is a summary of things collected from a variety of sources, > > but I think this coarse walk-through of issues gives some insight as to > > what issues pops up where and the milage vary a lot within each group. > > Modern high-performance rubidium gas-cells outperform the early > > caesiums, high-performance crystals outperform several rubidiums. > > The HP5065A is an example of an old clock with really good performance, > > so modern is not everything, and the modern compact telecom rubidiums > > and for that mater CSAC is more space/power oriented than ultimate > > performance of the technology as such. > > > I wonder where mercury ion fits in the scheme of things, since that's > where we're spending some money for spacecraft applications right now. > It's supposed to be orders of magnitude better than Rb. > > > _______________________________________________ > 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.