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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2010
- Accession Number
- ADA639437
Entities
People
- J. H. Shirley
- P. Kunz
- Steven R. Jefferts
- T. E. Parker
- T. P. Heavner
Organizations
- National Institute of Standards and Technology