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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 ] It used a model developed by NIST [ 5 ] to evaluate Doppler frequency shifts, known as distributed cavity phase, some believe to be incorrect. [ 6 ]
The main variety of atomic clock uses caesium atoms cooled to temperatures that approach absolute zero. The primary standard for the United States, the National Institute of Standards and Technology (NIST)'s caesium fountain clock named NIST-F2, measures time with an uncertainty of 1 second in 300 million years (relative uncertainty 10 −16 ...
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 ...
Cs fountain 2 × 10 −16 ... 18 cesium atomic clocks and 4 hydrogen maser clocks Cs, H National Institute of Information and Communications Technology; Koganei, ...
The idea of the atomic fountain was first proposed in the 1950s by Jerrold Zacharias. [6] [7] Zacharias attempted to implement an atomic fountain using a thermal beam of atoms, under the assumption that the atoms at the low-velocity end of the Maxwell–Boltzmann distribution would be of sufficiently low energy to execute a reasonably sized parabolic trajectory. [8]
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NIST-F1, a cesium fountain atomic clock used since 1999, has a fractional inaccuracy (δf / f) of less than 5 × 10 −16. The planned performance of NIST-F2 is δ f / f < 1 × 10 −16 . [ 3 ] At this planned performance level the NIST-F2 clock will not gain or lose a second in at least 300 million years.