[time-nuts] Question for the cesium nuts.

[Rick Karlquist]

Let me try to remember some of the answers to this question
that I heard from the cesium guys (I was only the RF guy on
the 5071A, so I know just enough about cesium to be dangerous :-)

The tubes rarely if ever fail because they run out of cesium.
Sometimes they fail because the electron multiplier wears out.
Other times that have a soft failure where they get noisier
and noisier.  This is possibly due to gradual build up of
contaminants.  Sometimes the ion pump will get overwhelmed.

If you were to open up a tube, you would find that all the components
are "cesiated".  Of course there is no way to clean them up.
Thus you cannot "recycle" tube components.  If you made a
tube with cesiated components, it would probably be noisy and
or not hold a good vacuum.

You would have to fix whatever broke in the first place, in
addition to replacing the cesium.  You would of course have to
replace the cesium whether it was used up or not because it
will burn up as soon as the vacuum is broken.  I am not sure
that the cesium oven lends itself to disassembly and reassembly.
Also, I think you would have to remove the wiring harness before
bake out and reinstall it, because of the high temperatures involved.

Rick Karlquist N6RK




Jack Hudler wrote:
> It seems to me that like all good things they must come to and end.
>
> If all CBTs have a life expectancy that varies depending on the
> manufacturer.
>
> What are we going to do when all the CBTs owned by amateurs start to end
> of
> life?
>
> I for one am certainly not going to buy one, not at those prices! (Unless
> I'm retired then that's another story)
> You only have calculate the time value of money for that CBT purchase over
> the remaining time to retirement; If that doesn't stop you dead in your
> tracks then this group really is aptly named! :)
>
> From my perspective, that of wanting to own a Cesium Standard; I don't
> really want to layout the monies for something that's going to end of life
> on me shortly (few years) afterwards.
>
> I know that handling (Caesium) Cesium-133 is tricky at best. It's a heavy
> alkali metal and contact with moisture is right out!
> Other than that it's not terribly difficult to create a safe environment
> to
> work with it.
>
> So there must be something else that's considerably more difficult than
> opening the tube, recharging the ampoule, resealing it, pulling an ultra
> high vacuum and baking it out.
>
> I've not seen any pictures of a naked CBT, still I'm not too worried about
> cracking the tube open if its Pyrex, unless resealing it caused the cesium
> beam collimation to be lost.
>
> Are there if any getters to worry about? If so, how would one ablate the
> contaminates of the surface?
>
> Anyone care to start a discussion on the merits of restoring a CBT to
> life?
>
> Jack
>
>
>
>
>
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