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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 ...
In a time period from 1959 to 1998, NIST developed a series of seven caesium-133 microwave clocks named NBS-1 to NBS-6 and NIST-7 after the agency changed its name from the National Bureau of Standards to the National Institute of Standards and Technology. [10] The first clock had an accuracy of 10 −11, and the last clock had an accuracy of ...
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]
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]
Accuracy Location Image CS1 [1] 1969 Cs 7 ... Caesium clocks, Hydrogen Maser [28] Cs Indonesian Institute of Sciences; Jakarta, ...
Like other caesium atomic clocks, the clock keeps time by a precise 9.192631770 GHz microwave signal emitted by electron spin transitions between two hyperfine energy levels in atoms of caesium-133. A feedback mechanism keeps a quartz crystal oscillator on the chip locked to this frequency, which is divided down by digital counters to give 10 ...
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The caesium atomic clock maintained by NIST is accurate to 30 billionths of a second per year. [206] Atomic clocks have employed other elements, such as hydrogen and rubidium vapor, offering greater stability (in the case of hydrogen clocks) and smaller size, lower power consumption, and thus lower cost (in the case of rubidium clocks). [ 206 ]