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
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