[time-nuts] How does it work?

J. Forster jfor at quik.com
Tue Jun 28 17:24:38 UTC 2011

You may be confusing a fountain and an ion trap with LASER cooling.

In an ion trap, the ion is in a potential well and interacts with the
cooling LASER beam which slows the ion down (in all 3 directions), thus
cooling it. The slower moving ion has less Dopplar, hence a better
frequency standard.

In a fountain, the ions sort of come out of a gun and they are probed
orthogonal to their flow direction. Because the beam is near collimated,
the sideways Dopplar is reduced a lot.

All very roughly speaking.



> For the sake of this poor, befuddled non-engineer, would one of you worthy
> gentlemen explain how it is that lasers striking a mass of cesium atoms
> and
> compressing them into a ball (in a cesium fountain) has the effect of
> cooling them to near absolute zero?  That seems counter-intuitive to me,
> but
> then I have virtually no education in this area.
> Thanks!
> Bill
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