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

[Anders Wallin]

In Cs my understanding is that a transition mF=0 to mF=0 transition is used
- so it is insensitive to the magnetic field[1].
There is no magnetic field insensitive component of the 88Sr+ clock
transition (other optical clocks will vary!)
See e.g. around page 10 here for an energy-level diagram:
http://resource.npl.co.uk/docs/networks/time/meeting3/klein.pdf

To measure 88Sr+ line-center (where there is no peak at nonzero B-field!)
the mid-point between a Zeeman pair is a good approximation, but one gets
rid of the electric quadrupole shift by measuring the center of three pairs
of components and calculating line-center from that. 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.

The BIPM SRS document has more references
https://www.bipm.org/utils/common/pdf/mep/88Sr+_445THz_2017.pdf

Anders

[1] Fig3 here
https://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/2003_Bauch_MST_CAC_VF_author_version.pdf


On Sat, Dec 7, 2019 at 10:04 PM paul swed <paulswedb at gmail.com> wrote:

> Hello to the group. This is great to watch and see the development of an
> exotic clock. I guess I need a bit of help in understanding what I am
> seeing. To a point I understand Zeeman images in respect to a cesium
> reference at least. But in that case there is a single higher peak thats
> the correct one to lock to. In the image thats shared is this a case of
> saying the multiple energy level can be seen but no attempt is being made
> to choose one peak to work with?
>
> Like the speed up version a bit to impatient.
> Thank you for sharing with time-nuts Anders
> Paul
> WB8TSL
>
> On Sat, Dec 7, 2019 at 7:39 AM Anders Wallin <anders.e.e.wallin at gmail.com>
> wrote:
>
> > Hi Jim, yes you are right  the background is a camera-image (about 30x
> > magnification, maybe 1um per pixel). We use a microscope-objective, a
> > narrow 422nm bandpass filter, then an image-intensifier, and a fairly
> > standard CCD camera that looks at the output of the intensifier. When
> > everything is working and optimized I think a good quality (high QE) CMOS
> > or CCD camera alone could work. I think it would be interesting to try
> e.g.
> > a budget camera made for astrophotography at some point.
> > If you have lots of money then an EMCCD camera (30-50k maybe) is a good
> > solution.
> >
> > The camera is only used for observation and coarse diagnosis of major
> > problems. For quantitative measurements we have a beam-splitter that
> > directs most of the fluorescence towards a pinhole followed by a PMT
> > photon-counter. The ARTIQ controller can time-stamp each incoming photon
> > with 1ns resolution (but this creates a lot of data) - mostly we just bin
> > the counts into some gate time and look at the time-series of counts per
> > 20ms or so.
> >
> > The live stream is created with OBS. It captures the camera image as
> > background and can overlay any images/websites etc. that we can imagine.
> > I create the Zeeman-spectrum barchart in matplotlib as a PNG image with
> > transparent background - once per minute, from data we store in InfluxDB.
> > The X-axis labeling was not so good - need to improve that next time.
> > Somehow indicate that line-center is 445THz and the peaks really are
> <1e-12
> > wide (narrow!).
> >
> > For the impatient, I made a speedup (128x) version of the live-stream:
> > https://www.youtube.com/watch?v=f3edhdwqXgc
> >
> >
> > Anders
> >
> > On Sat, Dec 7, 2019 at 1:48 AM jimlux <jimlux at earthlink.net> wrote:
> >
> > >
> > > > The central bright dot is fluorescence at 422nm from laser cooling a
> > > single
> > > > trapped 88Sr+ ion. The ion emits about 1e7 photons/s at most and we
> > > > currently detect about 500 of those in a 20ms detection window
> (using a
> > > > Hamamatsu PMT module).
> > >
> > > Very cool. A question about the display - it's a video image of the
> > > fluorescence, and the graph is superimposed on top of it?
> > >
> > >
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