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

[J. Forster]

http://www.peltier-info.com/info.html

-John

==============



> Hi
>
> The big hitters for heat outside the physics package seem to be the RF
> excitation and the microwave generation "stuff". The regulators will warm
> things up if you run high voltage into them, but I would probably not do
> that.
>
> I don't believe that putting multiple swimming pools into the basement,
> mercury filled or otherwise was ever a real candidate for a solution. It
> is kind of interesting to see just how big the "jug of water" would have
> to be.
>
> Right now my leading candidate is a multi layer aluminum / steel enclosure
> with a "point short" between each of the layers to keep the heat rise
> under control. Cool the "baseplate" with recirculating water and a cheap
> (< $50) pump. Throw in a fan and radiator to cool the water to room
> temperature.  Servo the temperature with "what ever" at the point shorts.
> Monitor the temperature as best you can.
>
> The main "what ever" still in there are TE coolers. A quick look suggests
> that +12 heats and -12 cools. In between the two it's not clear that much
> happens (maybe it does ...). Even if it does not, I haven't dug deep
> enough to see if something like current drive takes care of the dead band
> issue.
>
> Some math. It's late, but I think this is about right:
>
> 1) 4 layers
> 2) Shorts at 2 C/W
> 3) 10 W "inside"
> 4)  80 C heat rise - not going to work
>
> If I stick with 4 layers, 10 W, and a 15 C rise then the shorts need to be
> ~ 0.38 C/W.  A 15C rise gets me to 40C which looks reasonable based on the
> app notes I have read on the rubidiums.
>
> If the basement moves up 5 C then I'm cold pumping 1/3 of the 10W. Same
> thing in reverse if the basement drops 5 C. Both are unlikely to happen as
> long as there isn't a catastrophic failure of the HVAC.
>
> If I go to a air cooled baseplate heat sink, it's thermal resistance is
> going to have to come out of the budget.  My *guess* is that's going to be
> more involved than a simple pump and some plastic tubes.
>
> Bob
>
> On Dec 24, 2009, at 10:46 PM, Hal Murray wrote:
>
>>
>> lists at cq.nu said:
>>> The original intent was to simply take an existing "cheap" rubidium
>>> and do simple things to it. Tearing it into pieces and redesigning
>>> parts of it was not anything I originally contemplated. The tight
>>> integration of the physics package to the electronics would make this
>>> a fairly involved process.
>>
>> Sure, but if we are discussing digging a hole big enough for a ton of
>> mercury, then taking apart a tightly integrated package seems worth
>> considering.
>>
>> I expect the packaging might be reasonable for this purpose.  After all,
>> the
>> designers probably wanted to keep that heat away from the electronics.
>>
>>
>>
>> --
>> These are my opinions, not necessarily my employer's.  I hate spam.
>>
>>
>>
>>
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