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NIST F1 and F2



Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Paul D. Kunz, Steven R. Jefferts


The National Institute of Standards and Technology operates a cesium fountain primary frequency standard, NIST-F1, which has been contributing to International Atomic Time (TAI) since 1999. During the intervening 11 years we have improved NIST-F1 so that the uncertainty is currently δf/fo ≅ 3 × 10-16, dominated by uncertainty in the Blackbody radiation inducedfrequency shift. In order to circumvent the uncertainty associated with the blackbody shift we have built a new fountain, NIST-F2, in which the microwave interrogation region is cryogenic (80K) reducing the blackbody shift to negligible levels. We briefly describe here the series of improvements to NIST-F1 which have allowed its uncertainty to reach the low 10-16 level and present early results from NIST-F2.
Proceedings Title
PTTI Conference proceedings 2010
Conference Dates
November 15-18, 2010
Conference Location
Rastin, VA


atomic clock, frequency standards
Created November 15, 2010, Updated February 19, 2017