[time-nuts] chip scale atomic clock
Magnus Danielson
magnus at rubidium.dyndns.org
Wed Dec 30 02:25:03 UTC 2009
Peter Vince wrote:
> 2009/12/26 Robert Lutwak <Lutwak at alum.mit.edu>:
>> ...
>> CSAC is intended for portable battery-powered operation. Surely your
>> basement has the space and wallplug power to support an LPRO. (p.s. don't
>> cool the damn thing, heat it).
>> ...
>
> Hi Robert,
>
> Do I understand you are suggesting heating an LPRO, not cooling
> it? That seems to go against what I understood, that greater cooling
> leads to increased life.
While not directed to me, these are my understandings:
Besides the power applied to heat the Rb lamp, the physical package
needs to be at the sweet-spot in temperature, so heating is performed.
By lowering the cooling of the physical package, the powerconsumption
goes down. So better isolation has to cool of less effect.
This stands in contradiction to the lifetime of the electronics, but the
physical package and electronics have two different requirements.
> As an aside, a newbie question if I may: being so used to Caesium
> standards being THE reference, I was surprised to hear that the CSAC
> has an aging mechanism - can you say a few words to explain that
> please?
Don't confuse the stability and repeatability of elaborate beam clocks
with that of (cheaper) gas cell clocks. Rubidium and Thallium beams has
existed but Cesium was a better match for that purpose, Rubidium was
found more suitable for the simpler and cheaper gas cell standard.
Rubidium excells over Cesium in laser cooled fointains, since it reacts
better to the laser cooling. Thus, each technology finds different
technological balances with different atoms.
May one suspect that the gas cells buffert gas mixture and resulting
wall-shift/gas-shift balance is one of the long-term age effects, just
as with ordinary rubidium gas cells. Another aspect to consider is that
this clock does not have the C-field servo loop which modern cesium
beams have.
Then again, I think Robert can lecture a mere student (lazy such) to the
field like me.
Cheers,
Magnus
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