atomic clock
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...
that, along with
NIST-F1
NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took less than four ye ...
, serves as the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
' primary
time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...
and frequency standard.NIST Launches a New U.S. Time Standard: NIST-F2 Atomic Clock /ref> NIST-F2 was brought online on 3 April 2014.First Accuracy Evaluation of NIST-F2, T. P. Heavner, S. R. Jefferts, J. H. Shirley, T. E. Parker, E. A. Donley, N. Ashby, S. Barlow, F. Levi, and G. Costanzo, May 2014 /ref>
Accuracy
NIST-F1, a cesium fountain atomic clock used since 1999, has a fractional inaccuracy (δ''f / f'') of less than .
The planned performance of NIST-F2 is δ''f / f'' < . Als available from NIST directly At this planned performance level the NIST-F2 clock will not lose a second in at least 300 million years.
Evaluated accuracy
The evaluated accuracy (''u''''B'') reports of various primary frequency and time standards ar by the
International Bureau of Weights and Measures
The International Bureau of Weights and Measures (french: Bureau international des poids et mesures, BIPM) is an intergovernmental organisation, through which its 59 member-states act together on measurement standards in four areas: chemistry, ...
(BIPM).
The first in-house accuracy evaluation of NIST-F2 reported a ''u''''B'' of .Heavner T P, Donley E A , Levi F, Costanzo G, Parker TE, Shirley J H, Ashby N, Barlow S and Jefferts SR, “First accuracy evaluation of NIST-F2,” 2014 Metrologia 51, 174–182, May 2014 /ref> In March 2014 and March 2015 the NIST-F2 cesium fountain clock reported a ''u''''B'' of in the BIPM reports of evaluation of primary frequency standards.
The last submission of NIST-F1 to BIPM TAI was February 2016.
At the request of the Italian standards organization, NIST manufactured many duplicate components for a second version of NIST-F2, known as IT-CsF2 to be operated by the Istituto Nazionale di Ricerca Metrologica (INRiM), NIST's counterpart in
Turin
Turin ( , Piedmontese language, Piedmontese: ; it, Torino ) is a city and an important business and cultural centre in Northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital ...
,
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
NIST Time and Frequency Div. — 2004: Strategic Focus 1 (National Institute of Standards and Technology)
*
* {{cite web, title=Time gets an upgrade, url=https://www.newscientist.com/article/mg22229642-700-60-seconds/, website=newscientist.com, publisher=
New Scientist
''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publishe ...