Titelmasterformat durch Klicken bearbeiten Transportable Optical Lattice Clocks

Measuring Frequency #1 #2 Only the relation between reoccurring events can be measured Definition of the SI Second: The second is the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. => No frequency value given in Hertz can be more accurate than the cesium clocks The comparison of two frequencies can be characterized by two different quantities: Stability: does repetition of masurement lead to thesame result Accuracy: relation of value to the right value, in relation to a theoretical model

Clock Accuracy

Clock Stability

Comparing Sr to SI Frequency Comparisons in SI Units Comparisons of the Clock transition of 87 Sr with Cesium fountain clocks. On the level of 1E-15 everything seems to be fine But: Estimated uncertainty: 4E-17 => We need optical-optical Comparisons to be sure on that level. The values measured in these comparisons are frequency ratios without unit. => A redefinition of the second would be possible if we had more comparisons

Optical comparisons The number of these comparisons performed so far is small because the possible ways for remote comparisons on the 10E-17 level are still under development. Transportable clocks could be used for frequency comparisons If remote comparisons are possible transportable clocks could be used as a sensor for the gravitational potential of the earth Other interesting aspects of direct optical comparisons are: searching for possible variations of fundamental constants tests of general relativity

Relativistic Geodesy Gravitational redshift Simple picture: Total energy of a photon is conserved If it leaves a gravitational potential it is shifted to the red.  Clocks provide direct measurement of potential difference Hight difference of 1m at sea level leads to a shift of

Relativistic Geodesy The geoid is an equipotential surface of the gravitational potential of the earth. It is the best approximation to an unperturbed main sea level. © Deutsches GeoForschungsZentrum GFZ Data from CHAMP und GRACE The geoid depends on the exact mass distribution which changes in time and also on the tidal potential from sun and moon. To measure and to model the geoid is a challenging geophysical task. In classical geodesy it is not possible to measure directly the gravitational potential U but only the gradient of U – which is the acceleration.

Tidal Potential

LSM Modane – INRIM Turin 1200 m 240 m 100 km

How can you build a transportable lattice clock?

Building the clock Build Compact Laser Systems,…

Building the clock …, a compact vacuum chamber,…

Building the clock …, a lot more,…

Building the clock …and put in into a trailer.

What is the current status?

Results so far…