NIST F1 and F2

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 delta integral/integral(sub 0) approximately 3x10(exp -16), dominated by uncertainty in the blackbody-radiation-induced frequency 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 (80 K), reducing the blackbody shift to negligible levels. We briefly describe here the series of improvements to NIST-F1 that have allowed its uncertainty to reach the low 10-16 level and present early results from NIST-F2.

[1]  Steven R. Jefferts,et al.  First-Order Sideband Pulling in Atomic Frequency Standards , 2008, IEEE Transactions on Instrumentation and Measurement.

[2]  D. Calonico,et al.  Measurement of the blackbody radiation shift of the {sup 133}Cs hyperfine transition in an atomic fountain , 2004 .

[3]  Dai-Hyuk Yu,et al.  Power dependence of the frequency bias caused by spurious components in the microwave spectrum in atomic fountains , 2006, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[4]  Dai-Hyuk Yu,et al.  Microwave leakage-induced frequency shifts in the primary frequency Standards NIST-F1 and IEN-CSF1 , 2006, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[5]  André Clairon,et al.  Measurement of the Stark shift of the Cs hyperfine splitting in an atomic fountain , 1998 .

[6]  Wayne M. Itano,et al.  Shift of 2 S 12 hyperfine splittings due to blackbody radiation , 1982 .

[7]  S Bize,et al.  Controlling the cold collision shift in high precision atomic interferometry. , 2002, Physical review letters.

[8]  V. Dzuba,et al.  Frequency shift of the cesium clock transition due to blackbody radiation. , 2006, Physical review letters.

[9]  R Wynands,et al.  Cancellation of the collisional frequency shift in caesium fountain clocks. , 2007, Physical review letters.

[10]  G. Dick,et al.  Power dependence of distributed cavity phase-induced frequency biases in atomic fountain frequency standards , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[11]  R. Wynands,et al.  Effects of microwave leakage in caesium clocks: Theoretical and experimental results , 2006, Proceedings of the 20th European Frequency and Time Forum.

[12]  K. Beloy,et al.  High-accuracy calculation of the blackbody radiation shift in the 133Cs primary frequency standard. , 2006, Physical review letters.

[13]  Spatial phase variations in a TE/sub 011/ microwave cavity for use in a cesium fountain primary frequency standard , 1993 .

[14]  K. Gibble,et al.  Distributed cavity phase and the associated power dependence , 2005, Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005..

[15]  Claude Audoin,et al.  Frequency Offset Due to Spectral Impurities in Cesium-Beam Frequency Standards , 1978, IEEE Transactions on Instrumentation and Measurement.

[16]  Spatial variations of field polarization and phase in microwave cavities: application to the cesium fountain cavity , 1996, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.