[time-nuts] You can build a fountain from the things you find at home...

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Sep 27 20:58:37 UTC 2011

J. Forster wrote:
>> Boy I have to go back and check. I thought fountains used lasers and such
>> to slow the atoms down.
> That's a trap. "Optical molasses".
> A fountain essentially makes a beam and probes it orthogonal to the beam,
> where the Dopplar shifts are low. The beam basically makes all the atoms
> go in a single direction w/ no cross track velocities.
Caesium fountains actually use lasers to cool a "ball" of atoms and toss 
it upwards through the RF cavities etc.
Detection is by interrrogation of the ball, usually after it falls back 
down through the detector.
No continuous beam is involved. Using a relatively small number of atoms 
that have been laser cooled reduces the interactions between them.

> Are we speaking to some gas fountain without optics
>> much like a traditional CS standard?
>> Paul
> As to making one, I'd use stainless Conflat parts from eBay, used
> commercial pumps, feedthroughs, fittings, etc.  You can spend a lot of
> time trying to leak check home brew stuff.
Astenetic stainless has the problem of being slightly ferromagnetic.
> -John
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