[time-nuts] Pressure related rubidium oscillator aging

Attila Kinali attila at kinali.ch
Tue Aug 14 17:14:32 EDT 2018

On Tue, 14 Aug 2018 11:53:17 -0600
Skip Withrow <skip.withrow at gmail.com> wrote:

> So far, I have been operating in the 10-50 Torr range and have seen a
> very definite trend on aging with pressure.  But there is much more
> research to do.  My big question is - what pressure related mechanism
> might affect aging?  I would think that helium permeation would have a
> somewhat longish time constant.

I don't remember seeing any study of this. But then, I have not been
looking. I can think of a few causes for aging that might depend on
pressure. Beside helium there is also hydrogen that permeates the
glass wall. I don't know how large of an effect hydrogen has, though.
Additionally, there are impurities in the glass itself which move,
either due to Brownian motion or are carried by the gasses moving
through the glass (think gas chormatograph). 

Also keep in mind that deformation of glass is not instantaneous.
It if you change the outside pressure so much that you get into
the "vacuum" range, you will cause a lot of strain on the glass,
which in turn will lead to (inelastic) deformation (aka creep).

			Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neal Stephenson

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