[time-nuts] Symmetricon CS question
magnus at rubidium.dyndns.org
Fri Jun 24 11:46:44 UTC 2011
On 06/24/2011 07:39 AM, Perry Sandeen wrote:
> I’m still confused about the new Symmetricon CS unit. Is it truly a cesium primary standard or is it a secondary standard that happens to use cesium?
> IF it is truly a primary standard, is saving up the $1500 for one a better deal IN THE LONG RUN than getting a used HP or other brand C.S. unit? I’d want to use it and not have to fiddle with it to keep it running.
> Again, opinions welcomed
The CSAC is a secondary standard. It just happens to use Caesium.
A primary standard has a very high degree of repeatability in them, so
that systematic bias effects can be made very very small. This is not as
such connected to the atom being used as much as the technology being
used. A gas cell standard such as the rubidium gas cell, has systematic
pulling effects. Using temperature stabilization this pulling can be
stabilized, but there is no real method of within the standard detect
and compensate this pulling. Even the high quality beam of 5071 has
systematic effects, but engineered way down.
The CSAC is a caesium gas cell. It avoids some of the typical rubidium
gas cell issues by providing a significantly different physical package
design. It does not have an RF resonator chamber for instance, which
detuning from resonance causes a pulling effect. It has polarization
control to avoid that pulling effect (specific to laser excitation
rather than the non-coherent rubidium-lamp of normal optically pumped
rubidium cells) etc. Control-loops to stabilize various effects to
achieve a stable pulling.
But it is not a primary reference, rather it is a small sized and power
efficient secondary reference. If you view it like that, then you can
appreciate it for what it is and use it in the proper applications.
I like it and would like to try it out, but it will not replace a real
caesium beam by far.
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