[time-nuts] Cesium vs H Maser clocks

[iovane at inwind.it]

Tom,

The conceptual deadlock that I would overcome is whether adjusting the C-field the Cs resonance varies, as this would impact the defition of the "second".

Thanks,
Antonio I8IOV

> > What is the reference used to measure stability and accuracy
> > of H Masers?
> 
> Antonio,
> 
> Good question.
> 
> You compare against other H-maser(s), or an ensemble of Cs
> clocks, or high-precision coax, fiber, or two-way satellite links to
> other timing laboratories that happen to have much better clocks.
> 
> In general, when you have a really good clock in your lab, the
> obvious way to measure its performance is to find a clock that
> is 10x more accurate and compare your clock against it.
> 
> But if you can't find a better reference, or can't afford a better
> reference, or if a better reference doesn't even exist, then you
> use a different trick -- you make two or three clocks of the same
> design and compare them amongst themselves.
> 
> > Do Caesium clocks have something like a C-field adjustment 
> > (as Rb clocks have), and in the case, what it acts upon?
> 
> Yes, all commercial Cs clocks do have a C-field adjustment or
> an internal phase micro-stepper (frequency offset generator).
> This is useful since they are generally more stable (parts in 1e-13
> to 1e-15) than they are accurate (parts in 1e-12 to 1e-13). So
> the C-field is the traditional way to fine-tune the frequency of the
> clock. Modern Cs clocks find it easier (and perhaps more reliable)
> to adjust by synthesizer than by magnetic field.
> 
> On the other hand, laboratory Cs standards correct for all these
> systematic effects and are thus about as accurate as they are
> stable. If you'd like more details, let me know.
> 
> > Thanks in advance,
> > 
> > Antonio I8IOV
> 
> /tvb
> 
> 
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