about 20 years ago, JPL was operating a Hg ion clock at the Tidbinbilla tracking station just outside Canberra, Australia. I think they installed a few at various nodes in the Deep Space Network at the time. It operated for a few years but never reliably enough to be a useful UTC clock ( we were submitting the data to BIPM). I don’t know what happened to it.
Cheers Michael On Thu, 11 Jul 2019 at 3:01 am, jimlux <jim...@earthlink.net> wrote: > On 7/10/19 6:10 AM, Azelio Boriani wrote: > > Tom Van Baak said on Aug 29, 2013: > > > >> The pursuit of precision tends to be exponential rather than linear. > > ... > >> As a rough example in the ADEV world: > >> - for 1e-11, you can buy almost any XO, TCXO, or risky OCXO for $10. > >> - for 1e-12, you can find a reputable OCXO on eBay for under $100. > >> - for 1e-13, you can find an old but maybe working cesium clock for 1 > k$. > >> - for 1e-14, spend 10 k$ and get a certified working hp 5071A. > >> - for 1e-15, spend 100 k$ and find a used active H-maser. > >> - for 1e-16, spend 1 M$ to hire physicists and build a Cs fountain. > >> - for 1e-17, spend 10 M$ to fund a national research institute to build > ion or > >> optical clocks. > > > > > > Add the 1k USD running cost per year just to keep the active maser > running. > > I think that chances of finding an active H-maser used are near 0. > > Better to stick with GPSDOs: they bring into your home the stability > > and accuracy of the USNO UTC (well, close to...). > > > > > I wonder what it would cost to build a trapped Hg ion clock - I don't > think it's $10M, but it might be in the range of $500k-1M if you pay > people to do the work. Things like the quadrupole trap and ion sources > are catalog items. The whole vacuum system, including a turbo pump, is > probably in the $10k range (looking at the Cole Parmer catalog, first > hit on google), maybe another $5k in various vacuum plumbing bits and > pieces. > > back in 2005-2006 (published in 2007), Prestage et al had a lab version > https://ieeexplore.ieee.org/document/4319251 > > pumped, backfilled with Ne, then sealed > > > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.