[time-nuts] Cold Rubidium over hyped?

[Magnus Danielson]

Hi,

On 2019-11-09 01:07, Poul-Henning Kamp wrote:
> --------
> In message <AABQ6M5M5AL26S8J at smtpout01.dca.untd.com>, cdelect at juno.com writes:
>
>> Just wonder if some  5065A can get so impressive that they don't just
>> make a modern large/cool cell classic Rubidium with modern electronics
>> technology! Certainly would be cheaper and more long lived also.
> But isn't that essentially what they have done ?
Yes.
>
> The Rb-lamp-filter thing has been beaten to death.  Its not like
> people have not researched it in the last 50 years, but nobody
> anywhere have found a way to get rid of the Rb/glass absorption
> related aging or the pressure-sensitivity for that matter, so 5065
> performance pretty much is the best you can ever hope for there
> as long as your customers are terrestial.

The wall shift, the buffer gas shift, the resonator shift and how these
relate to environmentals in addition to the lamp intensity shift. All
well researched. Rubidium as such is not a bad species to measure, on
the contrary, we learned that it excels over cesium in laser cooled
state, as the cross-section is smaller.

>
> Given that these two cold-Rb devices are 1st generation of their
> kind and given how little time they have had to collect data on
> them yet, both with respect to performance but also day-to-day
> gremlin-wrangling, I wouldnt be at all surprised if the next
> two generations of that concept delivers almost two orders of
> magnitude improved performance.

Long-term measurements is being done at NIST and OP/SYRTE, none being
known to be extremely wreckless in this regard, to say the least.

This is well understood techniques now, so that it matures into
commercial products is not strange. It's worth noting that optically
probed cesium also exists from Oscilloquartz, altering the beam standard
techniques.

Common to all three clocks is the fact that they use semiconductor
lasers to pump and interact with the element, and therein lays also the
challenge of having such laser-systems operating long-term.

This is for sure the way forward, and these are just the for-runners of
the continiously operating optical clocks that may one day become
commercial products.

So, while hydrogen masers may work and large cell rubidiums can be
cleaned up, eventually we come to the point where these new techniques
will take over for many good reasons. Maybe one day we will have
time-nuts with cold rubidium clocks and maybe even optical clocks.

Cheers,
Magnus