There was discussion last October about the very tiny MEMS oscillators
failing from He leaking in. By now, there's several videos online
showing folks taking that MEMS oscillator and putting it in a chamber
and demonstrating the failure.
So here's something interesting - There are a remarkable number of
places with high atmospheric helium concentrations. And it causes a
variety of mystery failures.
The one of interest here is that helium can leak into a physics package
with Rb or Cs, and that changes a) the total pressure (which causes line
broadening, apparently) and b) the thermal conductivity of the vacuum.
The latter is of some concern to me, since I have some CSAC devices in
space that may have been exposed to a helium rich environment during
storage. The failure mode on a CSAC is that more heater power is needed
to keep the vapor pressure up, due to increased heat loss through the
"not as good a vacuum" in the physics package.
Has anyone on the list ever had a CSAC in a He-rich environment? Noticed
any performance differences?
I've asked Microsemi - their first response was that it's not something
they tested for and that the leak rate is very low. I suppose it's
probably in a hermetic can (which are *tested* with Helium leak tests)
Jim
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
