Posts Tagged ‘atomic clock

Experimental realization of an optical second …

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… with strontium lattice clocks

LNE-SYRTE optical to microwave measurement chain.

LNE-SYRTE optical to microwave measurement chain.

R. Le Targat et al
Progress in realizing the SI second had multiple technological impacts and enabled further constraint of theoretical models in fundamental physics.
Caesium microwave fountains, realizing best the second according to its current definition with a relative uncertainty of 2–4 × 10−16, have already been overtaken by atomic clocks referenced to an optical transition, which are both more stable and more accurate. Here we present an important step in the direction of a possible new definition of the second.
Our system of five clocks connects with an unprecedented consistency the optical and the microwave worlds. For the first time, two state-of-the-art strontium optical lattice clocks are proven to agree within their accuracy budget, with a total uncertainty of 1.5 × 10−16.
Their comparison with three independent caesium fountains shows a degree of accuracy now only limited by the best realizations of the microwave-defined second, at the level of 3.1 × 10−16….

Read also: Optical lattice atomic clock could ‘redefine the second’

Written by physicsgg

July 10, 2013 at 7:55 am


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Gyromagnetic Factors and Atomic Clock Constraints on the Variation of Fundamental Constants

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We consider the effect of the coupled variations of fundamental constants on the nucleon magnetic moment. The nucleon g-factor enters into the interpretation of the measurements of variations in the fine-structure constant, alpha, in both the laboratory (through atomic clock measurements) and in astrophysical systems (e.g. through measurements of the 21 cm transitions). A null result can be translated into a limit on the variation of a set of fundamental constants, that is usually reduced to alpha. However, in specific models, particularly unification models, changes in alpha are always accompanied by corresponding changes in other fundamental quantities such as the QCD scale, Lambda_QCD. This work tracks the changes in the nucleon g-factors induced from changes in Lambda_QCD and the light quark masses. In principle, these coupled variations can improve the bounds on the variation of alpha by an order of magnitude from existing atomic clock and astrophysical measurements. Unfortunately, the calculation of the dependence of g-factors on fundamental parameters is notoriously model-dependent….
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Written by physicsgg

July 30, 2011 at 8:30 am

Atomic clock is smallest on the market

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Symmetricom’s SA.45s Chip Size Atomic Clock

Researchers in the US have developed the world’s smallest commercial atomic clock. Known as the SA.45s Chip Size Atomic Clock (CSAC), it could be yours for just $1500. The clock, initially developed for military use, is about the size of a matchbox, weighs about 35 grams and has a power requirement of only 115 mW. Not your everyday timekeeper, the team behind the clock claim that it could have varied and wide-ranging applications, from disabling bombs to searching for oil.
Atomic clocks use a specific electronic transition frequency of an atom as a frequency standard, with the “ticks” being the oscillations between two energy states in an atom. Generally, a feedback loop is used to lock the frequency of a light source to that of the transition, thus creating a stable frequency standard….. Read the rest of this entry »

Written by physicsgg

May 12, 2011 at 12:02 pm


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