NIST F1 and F2
NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
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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 integralintegralsub 0 approximately 3x10exp -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.
- Operations Research
- Test Facilities, Equipment and Methods