[time-nuts] Mercury Ion Clock

[Jim Lux]

On 11/1/14, 9:08 AM, Magnus Danielson wrote:
> Paul,
>
> You mean, as all time-nuts already have redundant sites with at least 4
> 5071As with high-performance tubes, redundant cesium and rubidium
> fointains, set of active hydrogen masers, with everything in tight
> temperature, humidity and pressure control, UPS and diesel-engines,
> GPS/GLONASS/GALILEO receiver on temperature-stabilized piller and
> antenna, do TWSTFT to major labs... since money is no issue, right?
>
> The main problem with cesium tubes as I recall it is really the ionizer
> in the mass-spectrometer being poluted with cesium, this then creates
> bad S/N before running out of cesium in the oven.
>
> Yes, I agree it would be a great clock to have, but practical limits in
> cost is a challenge for most, so it would be interesting to look at it
> and ask how cheap it could be done.
>
>


Having been to a few of the design reviews and such for the DSAC, and 
before, when it was called the 1 liter atomic clock, etc.

I think one could build one *if* you have a fairly wide collection of 
skills, and you weren't hung up on it being tiny and low power, and zero 
maintenance.

For instance, building a perfectly sealed physics package that is space 
flight compatible is non-trivial. Most of us don't have e-beam welding 
equipment sitting around (nor does JPL.. we contract that kind of stuff 
out).  As Prestage points out in the article below, they started looking 
at how they build long life Traveling Wave Tubes for space (another 
precision ion optics device), and having spent some time in various TWT 
factories over the past 15 years: there is a lot of art in the 
manufacturing process.

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/41329/1/07-2003.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/41395/1/08-0610.pdf

However, if you were happy with "lab grade" construction, and you have 
the Kurt Lesker and Duniway catalogs as bedside reading, I think you'd 
have a chance.

The ion trap and such is a fairly straightforward thing, from what I 
understand: you need the usual vacuum pumps and such to build one.  If 
you don't want it to run for years without servicing, then issues of the 
mercury content are less important.
(BTW, the space clock uses thermal dissociation of HgO to get the mercury)

The PMT is an off the shelf thing. Check out the amateur built fusion 
reactor (fusor) websites on where to get PMTs and amplifiers (they're 
used behind a scintillator)

The 40 GHz stuff these days is not nearly as exotic as it used to be. 
The challenge might be test equipment when you're debugging your 40 GHz 
synthesis chain.



I don't think it would be *easy*, but I think doable, and nothing in the 
system is particularly expensive or that exotic.  It's sort of like 
telescope building.. The raw materials to make a 18" reflector telescope 
aren't all that expensive, nor is there some secret sauce: it's just 
time to grind the mirror (and recover from mistakes) and build the system.