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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 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]
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 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
The majority of the clocks involved are caesium clocks; the International System of Units (SI) definition of the second is based on caesium. [6] The clocks are compared using GPS signals and two-way satellite time and frequency transfer. [7] Due to the signal averaging TAI is an order of magnitude more stable than its best constituent clock.
Optical cesium atomic clocks - Oscilloquartz has developed optical cesium atomic clocks that are more stable and accurate than magnetic cesium-based solutions and exceed the current ITU-T G.811.1 enhanced primary reference clock (ePRC) specification. The current highest-end clocks in this range combine with core grandmaster devices to provide ...
The exact modern SI definition is "[The second] is defined by taking the fixed numerical value of the cesium frequency, Δν Cs, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s −1." [1]