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NIST F1: Recent improvements and a resulting accuracy of δf/f=0.53x10-15



Thomas P. Heavner, Steven R. Jefferts, Elizabeth Donley, Jon H. Shirley, Tom Parker


In the last several years we have made many improvements to NIST-F1 (a laser-cooled Cs fountain primary frequency standard) resulting in over a factor of 2 reduction in the uncertainty in the realization of the SI second. The two most recent accuracy evaluations of NIST-F1 had combined standard fractional uncertainties of 0.61 x 10-15 (June 2004) and 0.53 x 10-15 (January 2005) which were submitted to the BIPM with total fractional uncertainties (including time transfer contributions) of 0.88 x 10-15 and 0.97 x 10-15 respectively. Here we discuss the improvements, evaluation methods and present an updated uncertainty budget.


Cesium Standards (CES), General Time and Frequency (GEN), Time Scale (Scale), Time/The Second (SEC)


Heavner, T. , Jefferts, S. , Donley, E. , Shirley, J. and Parker, T. (2005), NIST F1: Recent improvements and a resulting accuracy of &#948;f/f=0.53x10<sup>-15</sup>, Metrologia, [online], (Accessed June 13, 2024)


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Created September 12, 2005, Updated October 12, 2021