[time-nuts] What does determine the short term stability of an Rb vapor cell standard?

[Bob kb8tq]

Hi



> On Mar 25, 2018, at 9:18 AM, Attila Kinali <attila at kinali.ch> wrote:
> 
> Moikka moi,
> 
> In the past, it has been again and again claimed that the HP 5065 has
> such an outstanding short term stability because of its large vapor cell.
> But the more I read, the less I believe this. E.g. if you look at the
> papers by the group around Gaetano Mileti and Christoph Affolderbach
> from University of Neuchatel, you'll see that they get an ADEV well
> below 1e-12 with a vapor cell that is just 3x3cm (actually smaller
> than that... but details). Yes, they use a laser instead of an Rb lamp,
> which increases SNR. But that would mean it's not the cell size per se
> that limits the short term stability, but the pumping of the atoms
> and the light noise on the photo cell. Hence it should be, theoretically
> at least, be possible, to take one of the telecom Rubidium standards,
> replace the lamp with something better, and come close to the performance
> of an 5065.... So, what part of this is wrong and what am I missing?

Well, magnetic shielding, temperature coupling between cells, photo detector
noise floor, phase noise of the various signals, basic stability of the “ocxo” and 
I’m sure a few other issues as well……

Bob

> 
> 
> 			Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
>                 -- Miss Matheson, The Diamond Age, Neil Stephenson
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