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Post Info TOPIC: Mercury Atomic Clock
Blobrana


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After conducting tests and assessments, the China National Institute of Metrology Science has declared that the latest NIM4 laser cooling - Caesium fountain clock is running reliably and stably. The uncertainty is as low as 55*10^-15, which means it will neither gain nor lose a second in more than six million years. This advanced device places China among the few countries in the world that have their own, independent, time-frequency system. The developers of the NIM4 laser cooling-Caesium fountain clock were recently given a National Science and Technology Advancement Award at a State Science and Technology Award Conference.
The unit(s) of the second is one of the seven most important basic physical quantities defined by the international system of units (SI). In 1967 the General Conference on Weights and Measures (Conference Generale des Poids et Mesures, CGPM) decided to change the definition of a second from the astronomy second to the caesium atomic second. Since then, the laboratory-caesium atomic clock has provided the basis for the definition of the second and become the benchmark device for measuring time and frequency. As a basic physical quantity, time frequency plays an important role in the national economy, defence and basic scientific research. Almost all scientific research requires precise time measurement. In last 10 years, 3 Nobel Prizes for Physics have been awarded for achievements related to time and frequency standards.

Source People's Daily

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Blobrana


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An experimental atomic clock based on a single mercury atom is now at least five times more precise than the national standard clock based on a “fountain” of caesium atoms, according to a paper by physicists at the Commerce Department’s National Institute of Standards and Technology (NIST) in the July 14 issue of Physical Review Letters.

The experimental clock, which measures the oscillations of a mercury ion (an electrically charged atom) held in an ultra-cold electromagnetic trap, produces “ticks” at optical frequencies. Optical frequencies are much higher than the microwave frequencies measured in caesium atoms in NIST-F1, the national standard and one of the world’s most accurate clocks. Higher frequencies allow time to be divided into smaller units, which increases precision.

A prototype mercury optical clock was originally demonstrated at NIST in 2000. Over the last five years its absolute frequency has been measured repeatedly with respect to NIST-F1. The improved version of the mercury clock is the most accurate to date of any atomic clock, including a variety of experimental optical clocks using different atoms and designs.

The current version of NIST-F1—if it were operated continuously—would neither gain nor lose a second in about 70 million years. The latest version of the mercury clock would neither gain nor lose a second in about 400 million years.

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