[time-nuts] 8th Symposium on Frequency Standards and Metrology
Magnus Danielson
magnus at rubidium.se
Sun Oct 18 21:50:44 UTC 2015
Hi,
I thought a small report might be appreciated.
It's been a very intensive week. Fellow time-nuts Attila Kinali and
Marek Peca attended. Attila and I hanged out with Florian Teply on
Friday after the sessions.
Anyway, in a sense of impeccable humor, the host of the conferance,
Fritz Riehle of PTB, had mounted a Black Forrest Coo-Coo clock on the
wall of the seminar room. This interrupted the nice overlook that David
Wineland (who got his Nobel price 2012) with amusement as result. I
ended up using the Coo-Coo clock as alternative time reference during
the seminar.
Among the interesting things said was that a group have now been formed
to look at the redefinition of the SI second in terms of the optical
clocks. The motivation is that since the last symposium, the optical
clocks have now with margin surpassed the microwave clocks. By the look
at the trend-curves, by the next symposium the distance should be
significant. Regardless, if a redefinition is to be done, there is a lot
of homework to be done before it can be settled and then we should
expect performance to have improved significantly.
Looking at the presentations, several contenders was presented, and it
is a wide range of approaches being done. Interesting is also how
comparison between both different implementation of a particular
transition but also between different transitions is done. Optical combs
has become a valuable tool in wide use and optical resonators of various
forms is used in combination to the various form of traps.
We see Sr, Yb, Al, Mg and Ca clocks being attempted and compared.
Numerous approaches to compare on distance was also presented, where PTB
is mighty proud of their new link which has a trend-line for 1E-19
downto 1E-19 in the modified Allan deviation plot. I naturally spotted
some systematics there, but they have good margin for the current
clocks, so it is impressive as it is. They have changed the laser
amplification method from EDFA to fiber-based, and their pump-lasers is
being locked too. The amplifier is a bit narrow-band, but does not look
to dominate the properties, so they are fine for now.
PTB and SYRTE have now a link between them to allow for comparison of
their clocks, and the NPL - SYRTE link will soon be completed. More
links in France is on-going as well as the link to INRIM. The SP - MIKES
link was listed also.
Several improvements in satellite two-way methods was also shown, and
people have already done test to compare optical clocks over existing
methods (which is limited by todays standard) but the new links coming
looks really promising for international comparison.
It was also interesting to see the presentation on cryogenic sapphire
whispering gallery oscillators.
One interesting project is what they call "NIST on a chip" which
attempts to provide not only frequency but several other units in form
of a chip-scale device. So, they are looking wider on how frequency can
be used in small form-factor, which will be of interest for length,
current, voltage etc.
Several groups have been looking at modified Ramsey interrogation by
applying a modified pulse-mechanism that helps to reduce the first
degree light shift. This new scheme is called hyper Ramsey interrogation
scheme. Another interesting technique being discussed was the
spin-squeezing, which promised an improvement in 20 dB.
Several presentations where on the topic of optical line measuring which
may not be of interest for clock transitions, but oh did the methods
being used share similarities!
One presentation was on the use of GPS satellites on detecting Dark
Matter. That guy ended up sharing lunch with us, and I think Marek and
me answered some of the questions he had about satellites and their
signals that he needed for his research. That we just "happen" to know
this, is another thing. :)
The breakfast, coffee breaks, lunches, poster sessions and dinners as
well as late night sessions all had lovely discussions. Phase noise,
cross-correlation issues and delta-counters effect on ADEV was among the
issues that came up regularly. Great fun with old and new friends.
I concluded that I have at least 3 papers to write as a consequence of
this trip.
NIST presented the work on chip scale clocks they are working on, and
one of their uses is in magnetic sensors. This had led them to test it
in PTBs lab for biosignals. PTB has built a room which is very very
quiet in terms of magnetic fields, so quiet in fact that it is the
magnetically quietest place in the solar system. Attila and me naturally
took the opportunity to visit this lab, as it was located relatively
central in Berlin. The building starts of with an EMC shield, and then
have large coils that not only cancels the earths magnetic field, but
also the fluctuations. Then they had built a room which has 7 layers of
mu-metal, really built as a box-in-a-box-in-a... and the door is an
interesting object in itself, as it slide sideways and connect all 7
layers at the same time. It took them 4 years to master the
demagnetization of the mu-metal, and it has been operational for 10
years now. Proud by friendly techs showed us what it can do and how it
reacts. Very cool indeed. They should be proud, it's an achievement. I
made the comparison to the things we do in atomic clocks.
They now have funding for an 8th layer of mu-metal to make the field
even more homogenic. Oh, the lights in there where optical bent pipes. :)
In all, quite an experience.
So, the field is moving, things are happening, it is quite interesting
future.
When I woke up at the hotel Saturday, all but one was gone. Strange
feeling, but I then got to meet a friend who now lives in Berlin, and
that warmed me up again. :)
Cheers,
Magnus
On 10/09/2015 08:54 PM, Magnus Danielson wrote:
> Fellow time-nuts,
>
> Next week is filled with interesting stuff as we gather in Potsdam for
> this:
>
> https://www.ptb.de/8fsm2015/about-the-symposium/
>
> I and Attila will be there, so who will join us?
>
> PS. For the moment I actually don't know how many Cs-clocks I have...
> it's complicated.
>
> Cheers,
> Magnus
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