[time-nuts] Cheap Rubidium

[Bruce Griffiths]

Bob

Some isothermal radiation (thermal) shields between the blanket and the 
top of the Rubidium source may also be required.

Unless you have a hydrogen maser you will need to use 3 rubidium sources 
each with its own engine block in order to determine AVAR (using the 3 
cornered hat technique).
FEI claim that their rubidium sources are actually quieter than typical 
caesium sources so using a caesium reference isn't as effective for 
measuring the short term (< 1day) stability.

Bruce

Bob Camp wrote:
> Hi
>
> I agree that if you simply bolt the rubidium to an old engine block and toss a blanket over it, you might get some pretty good thermal stability in the "hour to couple hours" time period. That's certainly a better approach than putting some kind of DC heater (and it's varying magnetic field) near the rubidium.
>
> I'm still wondering if they do indeed hit 1x10-13 (as in almost 1x10-14) or not. I suspect not. I'm sure that they do indeed get into the 1x10-13's, just not sure they get to the bottom of that region.
>
> Bob
>
>
> On Dec 22, 2009, at 8:26 PM, Bruce Griffiths wrote:
>
>    
>> Bob Camp wrote:
>>      
>>> Hi
>>>
>>> If I randomly pick up a FE 5680A data sheet, I find that it's short term stability is 1.4/sqrt(Tau) x 10-11.  Since I never doubt anything I see on a data sheet, this immediately tells me I should get 1.4x10-12 at 100 seconds, and I only have to wait for 10,000 seconds to get to 1.4x10-13.
>>>
>>> Since the temperature performance is at the 1x10-12 / C level, I would need a room that's stable to *much* better than 0.1 C over a 3 hour period to get there. I suspect that 0.01C might not be good enough ...
>>>
>>> So here's the question:
>>>
>>> Has anybody run any of the cheap rubidiums (FE or Efratom)  in a *very* stable temperature environment to see how close they get / what the floor is?  I've run through a lot of data on the web, but I haven't really found what I'm looking for.
>>>
>>> Thanks!
>>>
>>> Bob
>>>
>>>
>>>        
>> Figure 7 on the FE5680 page (also on the data sheet) indicates that you may need somewhat less than 3hours to achieve  ADEV ~1E-13.
>> 0.01C stability should be adequate.however its not necessary to control the room temperature to this stability if the FE5680 is in an enclosure with a sufficiently high time constant whilst having a sufficiently low thermal resistance so as to avoid overheating the FE5680.
>>
>> Bruce
>>
>>
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