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Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Paul D. Kunz, Steven R. Jefferts
Abstract
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.
Heavner, T.
, Parker, T.
, Shirley, J.
, Kunz, P.
and Jefferts, S.
(2010),
NIST F1 and F2, PTTI Conference proceedings 2010, Rastin, VA
(Accessed April 27, 2024)