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The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK [1] and promoted worldwide by Gernot M. R. Winkler of the United States Naval Observatory. Caesium atomic clocks are one of the most accurate time and frequency standards, and serve as the primary standard for the definition of the second in ...
The first clock had an accuracy of 10 −11, and the last clock had an accuracy of 10 −15. The clocks were the first to use a caesium fountain , which was introduced by Jerrod Zacharias , and laser cooling of atoms, which was demonstrated by Dave Wineland and his colleagues in 1978.
The evaluated accuracy u B reports of various primary frequency and time standards are published online by the International Bureau of Weights and Measures (BIPM). In May 2013 the NIST-F1 cesium fountain clock reported a u B of 3.1 × 10 −16. However, that BIPM report and the other recent reports are based on an evaluation that dates to 2005. [4]
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The first in-house accuracy evaluation of NIST-F2 reported a u B of 1.1 × 10 −16. [5] In March 2014 and March 2015 the NIST-F2 cesium fountain clock reported a u B of 1.5 × 10 −16 in the BIPM reports of evaluation of primary frequency standards. The last submission of NIST-F1 to BIPM TAI was February 2016. [6]
Accuracy Location Image CS1 [1 ... 18 cesium atomic clocks and 4 hydrogen maser clocks Cs, H ... SOC: Space Optical Clock breadboard (Sr lattice clock) [29] Sr lattice
Caesium (IUPAC spelling; [9] also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature .
They carried a commercial cesium clock back and forth from the National Astronomical Observatory of Japan in Mitaka, at 58 m (190 ft) above sea level, to Norikura corona station, at 2,876 m (9,436 ft) above sea level, corresponding to an altitude difference of 2,818 m (9,245 ft). During the times when the clock stayed at Mitaka, it was compared ...