[time-nuts] Rubidium oscillators and heatsinks

[Skip Withrow]

Hello Time-Nuts,
Just wanted to throw in my two cents worth on the rubidium oscillator
heatsink discussion.

My philosophy has always been - keep the rubidium oscillator mounting
surface in the 40-45C range and that is about as good as you can do.

My justification is as follows:
The physics package runs in the 100C range.  With no cooling the
entire oscillator will rise in temperature (as much as it can) to this
temperature.  As commercial components are rated 0-70C this is where
the shortened life comes in from elevated temperatures.
When a heatsink is provided that can keep the baseplate at 40C I
roughly figure the electronics is now at about an average between the
physics package and the baseplate, so about 70C (longer life).
Going overkill and cooling too much doesn't buy you anything (or at
least not much) because now the physics heaters are working extra hard
to maintain the physics package temperature.  This puts added stress
on these components so then they tend to fail faster.

In the end, there is an optimum baseplate temperature that minimizes
failure rate (not eliminates it).  You just have to do the best that
you can to determine what it might be.

Regards,
Skip Withrow