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

[Bob Camp]

Hi

Cool link - 

Thanks!

One of next steps is digging into the TE parts. One tradeoff is weather heavy cooling of the water (5C)  makes sense or not. One cooler for four units versus a bit lower conductivity shunts inside the enclosures... 

Bob

On Dec 25, 2009, at 1:36 AM, J. Forster wrote:

> 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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