[time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[Dana Whitlow]

Corby, I have a question to add regarding the HP units:  is the tip
temperature hot
enough to melt Rb in addition to providing vapor?  If so, doesn't the
orientation of
the physics package in earth's gravity have to be about correct in order to
keep
the excess Rb in the tip?

Thanks,

Dana


On Sat, Oct 26, 2019 at 4:01 PM <cdelect at juno.com> wrote:

> JF, Reference your statement:
>
> "Sorry, but I don't agree with your first statement about the 5065A :
> after long use, the rubidium plates on the inner envelope of the lamp
> (like silver on a mirror) and years after years the Rb light and photo I
> decreases."
>
> After working on the 5065A for over 40 years and across the full range of
> Serial numbers and ages of instruments (somewhere over 70 units) I have
> only seen Rubidium plated on the inside of the bulb twice. All the other
> lamps provided performance that met the HP specifications. The design of
> the lamp assy causes the tip of the lamp to be cold compared to the bulb
> causing the majority of the Rubidium to condense into the tip.
>
> The two bulbs were in units where the lamp oven winding shorted and
> "cooked" the lamp Assy.
> Those two bulbs were recovered using a heat gun.
> I suppose if the unit was stored for years in a very hot environment the
> Rubidium could get out of the tip but as long as the lamps starts you can
> just let it run for a week or so and it will condense back into the tip.
>
> If a you have a bulb that exhibits the plating I would recommend that you
> measure the lamp oven temperature to make sure it is not too hot. Also
> the two nuts on the lamp assy. rod that protrudes out of the cover should
> clamp the outer cover firmly between them. The outer cover is a heat sink
> for the lamp assy. and maintains the Rubidium in the tip. Operating for
> years without this clamping might cause what you saw.
>
> Other units specifically the Efratom FRS were poorly designed and are
> known for this problem.
>
> Cheers,
>
> Corby
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