Both the lamp and the absorption cell contain rubidium.
The rubidium in the lamp is slowly absorbed by the glass container.
The rubidim in the absorption cell is mixed with a buffer gas and
presumably has a much lower rate of absorption by the cell walls.
The rubidium lamp becomes unusable due to rubidium absorption long
before the absorption cell rubidium is depleted.
This lamp wear out mechanism is avoided if one uses laser interrogation
of the absorption cell.
Bruce
Alan Melia wrote:
They probably dont want the little rascals bumping into one-another and
broadening
the resonance line :-))
Alan G3NYK
----- Original Message -----
From: "Mike S"<mi...@flatsurface.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Monday, November 23, 2009 9:10 PM
Subject: Re: [time-nuts] Rubidium standard
At 03:24 PM 11/23/2009, Poul-Henning Kamp wrote...
There are no "rubidium crystals" involved.
Next you'll try and tell us that you can't make a clock run backwards
by using dilithium crystals, and making it warp time.
My understanding is that the Rb gets absorbed into the glass envelope,
so that eventually there isn't enough to provide proper operation. Rb
isn't that expensive (you can buy 1 g for $100 at retail -
http://elementsales.com/pl_element_grp1.htm ), so I'm not clear on why
they don't just put more than ~0.001 g in to begin with.
www.spectratime.com/product_downloads/life_mtbf.pdf
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