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Search Publications by: Tom Parker (Assoc)

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Displaying 126 - 150 of 268

A single-atom optical clock with high accuracy

July 14, 2006
Author(s)
Windell Oskay, Scott A. Diddams, Elizabeth A. Donley, Tara M. Fortier, Thomas P. Heavner, Leo W. Hollberg, Wayne M. Itano, Steven R. Jefferts, M J. Jensen, Kyoungsik Kim, F Levi, Thomas E. Parker, James C. Bergquist
For the past fifty years, atomic frequency standards based on the cesium ground-state hyperfine splitting have been the most accurate timepieces in the world. One of the most accurate, current-generation, cesium standards is the NIST-F1 fountain, which has

Absolute Optical Frequency Measurements with a Fractional Uncertainty at 1 x 10 -15

June 5, 2006
Author(s)
Jason Stalnaker, Scott A. Diddams, Leo W. Hollberg, Kyoungsik Kim, Elizabeth A. Donley, Thomas P. Heavner, Steven R. Jefferts, Filippo Levi, Thomas E. Parker, James C. Bergquist, Wayne M. Itano, Marie J. Jensen, Luca Lorini, Windell Oskay, Tara M. Fortier, J Torgerson
We report the technical details specific to our recent measurements of the optical frequency of the mercury single-ion clock in terms of the SI second as realized by the NIST-F1 cesium fountain clock. In these measurements the total fractional uncertainty

Comparison between frequency standards in Europe and the USA at the 10 -15 uncertainty level

February 1, 2006
Author(s)
Joseph Achkar, Andreas Bauch, R Dach, R Hlavac, Luca Lorini, Thomas E. Parker, G. Petit, Dirk Piester, P Uhrich, K Szymaniec
Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), National Institute of Standards and Technology (NIST), National Physical Laboratory (NPL), Laboratoire National de Metrologie et de Essais?Observatoire de Paris/Systemes de Reference Temps Espace

NIST F1: Recent improvements and a resulting accuracy of df/f=0.53x10 -15

September 13, 2005
Author(s)
Thomas P. Heavner, Steven R. Jefferts, Elizabeth Donley, Jon H. Shirley, Tom Parker
In the last several years we have made many improvements to NIST-F1 (a laser-cooled Cs fountain primary frequency standard) resulting in over a factor of 2 reduction in the uncertainty in the realization of the SI second. The two most recent accuracy

Operation of the NIST-F1 Cesium Fountain Primary Frequency Standard with a Maser Ensemble

September 13, 2005
Author(s)
Thomas E. Parker, Steven R. Jefferts, Thomas P. Heavner, Elizabeth A. Donley
The operation of a caesium fountain primary frequency standard is greatly influenced by the characteristics of two other important capabilities. The first is a stable frequency reference and the second is the frequency-transfer system. A stable frequency

A New Microwave Synthesis Chain for the Primary Frequency Standard NIST-F1

August 29, 2005
Author(s)
Thomas P. Heavner, Steven R. Jefferts, Elizabeth A. Donley, F Levi, Thomas E. Parker
We present the design and measurements of the microwave synthesis chain presently used in NIST-F1, the laser-cooled cesium fountain primary frequency standard in operation at NIST, Boulder, CO. This system has been used in two accuracy evaluations of NIST

Sources of Instabilities in Two-Way Time Transfer

August 29, 2005
Author(s)
Thomas E. Parker, Victor S. Zhang
Two-Way Satellite Time and Frequency Transfer (TWSTFT) has become an important component in the international system for comparing time and frequency over long distances. In order to make further improvements in the stability of TWSTFT a more complete

Time and frequency dissemination using GPS: Recent improvements

November 1, 2004
Author(s)
Tom Parker, Demetrios Matsakis
This is an article for a general audience that reviews recent imporvements in time and frequency delivery by the Global Positioning System (GPS). A significant improvement in direct time delivery was achieved when Selective Availability (SA) was turned off