[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