[time-nuts] Cheap Rubidium (heatpipe cooling for)

[Bob Camp]

Hi

I looked at it that way for quite a while. More or less: A rubidium is like an OCXO, and running it at the upper end of the specified range is just fine.

Then I cooked a few rubidiums ....

The real answer appears to be that the "rest" of the circuitry in there drops MTBF quickly as it gets hotter. The cell runs just fine, but the circuits that drive it die. There are tables in the data sheets that pretty well document this. 

Since these gizmos already have been out in the field for a while, I need to get all the life I can out of them.

Bob


On Dec 24, 2009, at 4:59 PM, Hal Murray wrote:

> 
>> A heat pipe might work if the fluid had a sufficiently low boiling
>> point. The rubidium isn't terribly tolerant of high temperatures, and
>> I'm going to pick up some heat rise as I put it inside some baffles /
>> shields. You need to find something that fits a fairly narrow window.
> 
> This is all backwards.
> 
> The main reason the typical Rubidium box needs a serious heat sink is that 
> there is an active heater inside it heating up the lamp to get it up to 
> operating temperature.  That part of the system better be "tolerant" of high 
> (enough) temperature.
> 
> Maybe things would be a lot better/simpler if the heating/cooling we have 
> been discussing were split into two sections.  One for the lamp assembly, and 
> a second for the electronics.
> 
> 
> Anybody know what the thermal coefficient of the lamp is relative to the 
> electronics?
> 
> 
> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.
> 
> 
> 
> 
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