Hi,
It's a complex picture as depending on temperature of the components,
and other aspects such as RF intensity, sensitivity to this or that
changes, line with changes etc. It also depends on the actual buffert
gas mix, which by the way changes over time due to leakage.
There is really three parts, the lamp, the filter and the detector cell.
Turns out that the filter and cell temperatures end up in about 65
degrees C. For some I've seen 73 degrees C. For the lamp, you end up
with something in 110-120 degrees C. Physically these two temperatures
is just next to each other, as the lamp needs to shine straight into the
microwave cavity of the cell but the filter cell needs the same
temperature as the cell.
One can optimize the temperatures for strongest signal, which sounds
like a good thing for S/N, one can optimize them for minimal sensitivity
for lamp or RF intensity or you can optimize it for low line width.
Depending on the conditions, you end up with a bit different settings.
If it is easy to stabilize RF intensity for instance, then one can relax
that optimization, similarly for lamp intensity. Then you can push it
for a balance between line-width (Q) and S/N. For others, this is not
feasible, for instance for simplicity/cost and/or size.
Regardless, temperatures of rubidiums is quite a different mess to that
of cesiums or hydrogen masers, and let me tell you that temperature of
the later is a mess I look at quite a bit at the moment.
Cheers,
Magnus
On 2021-10-05 17:45, Bob kb8tq wrote:
Hi
Rubidiums are somewhat unusual beasts. They typically have two heated zones ( =
two ovens) in
them. One is a bit hotter than the other. Because of the basic physics, those
ovens are right next
to each other / in contact with each other.
If you go to crazy with the insulation, the “colder” oven will heat up due to
heat leakage from the
“hotter” oven. You need a certain amount of heat coming off the package to
allow this to happen.
The bigger issue is that there is a pretty big batch of electronics near the
ovens in the typical telecom
Rb. Unless you heatsink things pretty well these parts heat up. When they do
their MTBF drops
quite a bit. You save a couple of watts of heat (maybe) and loose the Rb after
a year or two. Not
a great tradeoff.
Yes, there are a lot of different designs for lab grade Rb’s. There are also
some really tiny little
guys running around. Neither category is all that easy to get on the surplus
market. If you want
to dive into either of those categories, there are issues, they just may not be
quite the same.
Bob
On Oct 4, 2021, at 1:39 PM, Wim Peeters <peeter...@scarlet.be> wrote:
Insulation decreases the power consumption. But it will also increase the
temperature of the electronics.
A heath-sink will cool the electronics but will increase the power consumption.
Or maybe insulate the part of the case that gets hot, and put a heat-sink on
the other parts?
Wim Peeters
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