[time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs

[Jim Lux]

On 5/5/13 10:05 AM, Magnus Danielson wrote:
> On 05/05/2013 06:50 PM, Jim Lux wrote:
>> On 5/5/13 8:42 AM, Richard (Rick) Karlquist wrote:
>>> At HP in the 1990's, Len Cutler's group built some experimental
>>> mercury ion standards for USNO (IIRC). They were of the
>>> trapped ion type. BTW, it is important to understand that
>>> the architecture is the key factor, not the flavor of atom.
>>> When people say rubidium is inferior to cesium, they really
>>> mean a gas call is inferior to an atomic beam, etc.
>>>
>>>
>> OK, that's interesting..
>>
>> So the Hg ion they're building for Deep Space Atomic Clock (DSAC) is a
>> trapped ion type. The whole thing is, as I recall, 1 liter, 1 kilo,
>> including both the physics package and the electronics.
>>
>> It's targeting USO type applications.
>
> They have been targeting this goal for a very long time. Several
> interesting papers is to be found at PTTI, NIST etc.
>

Yeah.. some years (6 or 7?) ago, John Prestage had a prototype of the 
physics package working on the bench. Getting from there to a repeatably 
manufacturable space flight qualified has been a few years. Not to 
mention making flight qualified electronics to go around it.  I think 
the first flight will be next year or the year after as a hosted payload 
on something.