The "magic" of Rb in a gas cell standard is that you
can make an optical filter cell out of radioactive
Rb87 isotope that allows you to selectively optically pump
to the quantum level you need. It is just "luck"
that the absorption line falls where you need it.
And the RF pumping is at a doable 6.8 GHz.
I think the CSAC uses lasers so all of this doesn't
apply.
Cesium of course is part of the definition of the second,
so it's good to use for that reason.
It is a different discussion as to why Cs was chosen
to define the second, but the line being at 9.2 GHz might have had
something to do with it. That's a doable frequency in terms
of technology 60 years ago.
Rick N6RK
On 4/11/2017 1:54 PM, jimlux wrote:
On 4/11/17 12:34 PM, Attila Kinali wrote:
Hoi Jim,
On Tue, 11 Apr 2017 07:30:38 -0700
jimlux <jim...@earthlink.net> wrote:
I'm looking for a link to point to an explanation (at a basic level) of
the difference between Rb and Cs references, and what the tradeoffs are.
I googled a bit, but all I got were some explanations of the differences
in things like vapor pressure, etc.
What exactly are you looking for? A comparison of Rb vapor cell
standards vs Cs vapor cell standards? Or a general comparison
why different kind of standards are built with Rb and Cs?
For the former, there is a paper that has some of the details
why Cs was choosen over Rb for the CSAC in one of the papers.
(Which I currently cannot find...)
For the latter, there is no easy answer and a lot come from
technicalities (difference in handling) and what people were
able to build. There are some fundamental differences in which
elements get you what kind of stability for different kinds of
atomic clocks, but I have seen very little on that and it's quite
spread over various papers and books.
precisely why I asked..
The wikipedia article isn't bad in terms of covering the gas cell vs
beam in words, but I was hoping for something with pictures..
Encyclopedia Brittanica, perhaps.. except that they only talk about
caesium beam
Attila Kinali
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