[time-nuts] Cheap Rubidium

Bob Camp lists at cq.nu
Wed Dec 23 20:08:49 UTC 2009


Hi

Well so much for my plans to corner the mercury market and ultimately become
a super fund site...

I had the conversation about "heater blankets" back a while ago. Apparently
the magic printed circuit board like heaters have a much lower magnetic
signature than a twisted pair of heater wire. I didn't dig into it at the
time, and simply accepted it as being true. I'm hoping I can get away with
twisted pair heater wire....

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bruce Griffiths
Sent: Wednesday, December 23, 2009 2:58 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Cheap Rubidium

Bob Camp wrote:
> Hi
>
> So if I want to set up 4 uncorrelated systems, that would require 20 tons
of
> water split into 4 tubs. Each tub would be roughly 3' x 4' x 15'. Of
course
> if they are all in the same basement, I still have a correlation problem.
My
> guess is that no matter what I do, any system that controls all the
systems
> the same way will run into correlation.
>
> Oils, silicon fluids, and the like mostly hold less heat than water so the
> tubs would get bigger. Maybe a few tons of mercury...
>    
Try about 145 tons of mercury per rubidium source as the specific heat 
of mercury is about 1/29 that of water.
The redeeeming feature is that it will only occupy about 2.14x the volume.
The specific of some oils may be as large as 1/2 that of water however 
the density is around 10-20% lower.

> Active heat control and a rational heat sink is sounding like a better
> approach...
>
>    
Distributed heating using wire wound or printed heaters perhaps, but to 
reduce the associated magnetic field bifilar winding should be considered.
The major limitation is that the 25W or so dissipated by the rubidium 
source has to be transferred to ambient without raising the rubidium 
temperature too much.
This limits the maximum thermal resistance between the baseplate and 
ambient that can be safely used.
> Bob
>
>    
Bruce



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