[time-nuts] 88Sr+ ion-clock live stream

[Anders Wallin]

>
>  The servo-loop will
> > thus need to probe the left and right side of multiple peaks in sequence.
> > Our pulse-sequence now does 100 probe-pulses in about 7 seconds. If we
> > probe left/right side of three pars (twelve frequencies in total) the
> > line-center can be computed about once per minute. The ultra-stable clock
> > laser acting as local oscillator needs to maintain stability on its own
> > during those 1-2 minutes.
> >
>
> How do you then divide down the optical frequency and shim with the
> computed offset?
>

In our current setup we lock the frequency comb to a hydrogen maser (100MHz
output), and the comb measures the clock-laser light before the final
"zeeman-AOM" that does the hopping to find the peaks.
We don't produce a physical signal with the line-center frequency, but if
we want to compare the maser to the ion this isn't required. Instead we
take the frequency-comb measurement and add the computed line-center
measurement - this gives us a comparison between the maser and the ion. The
maser in turn is linked to UTC(k), which is linked through GNSS/PPP to UTC.
There are methods to lock a frequency-comb to the ultra-stable clock laser
and get as output microwaves (0.1 to 1 GHz) that are divided down (by 2e6
or so) from the optical carrier - we are not doing this at the moment. For
the ion vs maser comparison this second method would not significantly
improve things (I think).

Anders



>