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

[Attila Kinali]

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?


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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Re: [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  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
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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

[Dana Whitlow]

Could it be that with the narrow-band laser emission the dip in
light transmission of the Rb cell is significantly improved?   I know
that diode lasers are generally not paragons of virtue when it comes
to intensity noise, so I'm wondering what accounts for the claims of
better SNR with laser illumination.

Dana Whitlow

On Sun, Mar 25, 2018 at 8:18 AM, Attila Kinali  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?
>
>
> 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
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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