We report the first accuracy evaluation of NIST-F2, a second-generation laser-cooled Cesium fountain primary standard developed at the National Institute of Standards and Technology (NIST) with a cryogenic (Liquid Nitrogen) microwave cavity and flight region. The 80 K atom interrogation environment reduces the uncertainty due to the Blackbody Radiation (BBR) shift by more than a factor of 50. Also, the Ramsey microwave cavity exhibits a high Q (>50,000) at this low temperature, resulting in a reduced distributed cavity phase shift. NIST-F2 has undergone many tests and improvements since we first began operation in 2008. In the last few years NIST-F2 has been compared against a NIST maser time scale and NIST-F1 (the US primary frequency standard) as part of in-house accuracy evaluations. We report the results of nine in-house comparisons since 2010 with a focus on the most recent accuracy evaluation. This paper discusses the design of the physics package, the laser and optics systems, and the accuracy evaluation methods. The Type B fractional uncertainty of NIST-F2 is shown to be 0.11 × 10-15 and is dominated by microwave amplitude dependent effects. The most recent evaluation (August 2013) had a statistical (Type A) fractional uncertainty of 0.44 × 10-15.
First Accuracy Evaluation of NIST-F2 / Thomas P. Heavner; Elizabeth A. Donley; Filippo Levi; Giovanni Costanzo; Thomas E. Parker; Jon H. Shirley; Neil Ashby; Stephan Barlow; S. R. Jefferts. - In: METROLOGIA. - ISSN 0026-1394. - STAMPA. - 51:3(2014), pp. 174-182.
|Titolo:||First Accuracy Evaluation of NIST-F2|
|Data di pubblicazione:||2014|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1088/0026-1394/51/3/174|
|Appare nelle tipologie:||1.1 Articolo in rivista|
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