Hi Very interesting
Thanks!! Bob > On Oct 18, 2015, at 5:50 PM, Magnus Danielson <[email protected]> wrote: > > 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. The y 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 > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
