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~800Hz wide clock-transition in 88Sr+

Here's the latest preliminary result from the VTT MIKES 88Sr+ ion clock (in case you missed the live-stream!):

-C2 component of the clock transition at 445 THz in 88Sr+

This shows a ~2 kHz slice (left axis, double the 1 kHz shown, because we plot the input frequency of a double-pass AOM) of the optical spectrum around 445 THz, where we expect to find the -C2 Zeeman component of the clock-transition in 88Sr+ (a secondary representation of the SI second). The right axis shows the probe-pulse length in seconds, where we see only a few percent excitation (z-axis) at short pulse lengths, but a clearer signal up to >10% at longer probe pulse lengths of 40 and 50 ms.

It ain't pretty, but considering the carrier is at 445 THz, this noisy and broad looking 800 Hz wide peak is still a measurement to a relative level of 2e-12. When fully operational a line-width of <10 Hz (2e-14) is expected.

Our experiment now has one metglas magnetic shield. This particular Zeeman component (-C2) has a sensitivity of 11 kHz/uT, so the observed linewidth of 800 Hz could be caused by a low-frequency AC magnetic field with an amplitude of 30-40 nT or so. We think the remaining DC-field is around 1.6 uT (down from 66 uT without the metglas shield).

Among other improvements, next is building a second metglas shield, to reduce AC fluctuations in the magnetic shield even further. Stay tuned...

Trapping again

Since about July 15th our single-ion experiment has been in maintenance-mode, but today again some trapping!

The central 'pale blue dot' is a single 88Sr+ ion trapped between the inner electrodes (cylindrical) which are driven with a ~400 Vpp ~16 MHz sine-wave to create a Paul trap. The outer conical electrodes are grounded. The window-reflections of the 422nm cooling laser create the larger circular spots in the top half of the picture. A single laser-cooled 88Sr+ ion emits around 10 million photons per second, making it easily visible on 1s or longer exposures with a DSLR. Sigma 105mm/F2.8 macro objective with a short (13mm?) extension-tube.

Live stream:

Mowing season end

In 2018 the automower worked for 516 hours. By October 2019 the count is at 960 hours, so it has worked 444 hours during the 2019 season.

The outer shell is removable - so all the grass clippings can be cleaned off...

Time for a winter break, back to work in May 2020.

Iltarastit Paloheinä

The last Iltarastit event for this year. A bit wet in the forest after all the rain lately. I did have my garmin-watch but it somehow managed to forget this run completely - so a hand-drawn route instead.

uBlox F9T qErr correction

Here's a test of how to correct the 1PPS signal out of an F9T with the qErr-value from the UBX-TIM-TP message.

When the time-interval-counter is configured with start=reference-clock, stop=uBlox, the qErr is applied with a + sign to the measured time-interval - resulting in much smoother data for averaging times up to tau=1000s.

Iltarastit Solvalla

Around +12C with a bit of rain before the run. Large 1:7500 map. Almost ran past both the 1st and 2nd controls...

uBlox F9T test

Test of the 1PPS stability of an uBlox F9T dev-kit RCB-F9T

Länsirastit Kasavuori

A bit of night orienteering on a small area with lots of controls.

Itärastit Ämmässuo

Long time no run..

Firmaliiga Salmi

warm, over +20C. My Garmin watch didn't get a GPS-fix at the start and it took until #3 for it to start recording.

No major mistakes but not so great running/fitness.

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