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Search Publications by: Tom Parker (Assoc)

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Displaying 1 - 25 of 134

A Resilient Architecture for the Realization and Distribution of Coordinated Universal Time to Critical Infrastructure Systems in the United States: Methodologies and Recommendations from the National Institute of Standards and Technology (NIST)

November 3, 2021
Author(s)
Jeffrey Sherman, Ladan Arissian, Roger Brown, Matthew J. Deutch, Elizabeth Donley, Vladislav Gerginov, Judah Levine, Glenn Nelson, Andrew Novick, Bijunath Patla, Tom Parker, Benjamin Stuhl, Jian Yao, William Yates, Michael A. Lombardi, Victor Zhang, Douglas Sutton
The Time and Frequency Division of the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce (DOC), was tasked with fulfilling Section 4, Part (i) of the Position, Navigation and Timing (PNT) Executive

Frequency Ratio Measurements with 18-Digit Accuracy Using a Network of Optical Clocks

March 24, 2021
Author(s)
Kyle Beloy, Martha I. Bodine, Tobias B. Bothwell, Samuel M. Brewer, Sarah L. Bromley, Jwo-Sy Chen, Jean-Daniel Deschenes, Scott Diddams, Robert J. Fasano, Tara Fortier, Youssef Hassan, David Hume, Dhruv Kedar, Colin J. Kennedy, Isaac Kader, Amanda Koepke, David Leibrandt, Holly Leopardi, Andrew Ludlow, Will McGrew, William Milner, Daniele Nicolodi, Eric Oelker, Tom Parker, John M. Robinson, Stefania Romisch, Stefan A. Schaeffer, Jeffrey Sherman, Laura Sinclair, Lindsay I. Sonderhouse, William C. Swann, Jian Yao, Jun Ye, Xiaogang Zhang
Atomic clocks occupy a unique position in measurement science, exhibiting higher accuracy than any other measurement standard and underpinning six out of seven base units in the SI system. By exploiting higher resonance frequencies, optical atomic clocks

Measurement of the 27Al+ and 87Sr absolute optical frequencies

January 21, 2021
Author(s)
Holly Leopardi, Kyle Beloy, Tobias B. Bothwell, Samuel M. Brewer, Sarah L. Bromley, Jwo-Sy Chen, Scott Diddams, Robert J. Fasano, Youssef S. Hassan, David B. Hume, Dhruv Kedar, Colin J. Kennedy, Isaac H. Khader, David R. Leibrandt, Andrew D. Ludlow, William F. McGrew, William R. Milner, Daniele Nicolodi, Eric Oelker, Thomas E. Parker, John M. Robinson, Stefania Romisch, Jeffrey A. Sherman, Lindsay I. Sonderhouse, William C. Swann, Jian Yao, Jun Ye, Xiaogang Zhang, Tara M. Fortier
We perform absolute measurement of the 27Al+ single-ion and 87Sr neutral lattice clock frequencies at the National Institute of Standards and Technology and JILA at the University of Colorado against a global ensemble of primary frequency standards. Over

Optical-Clock-Based Time Scale

October 30, 2019
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Andrew D. Ludlow, Holly Leopardi, Thomas E. Parker, William F. McGrew, Scott A. Diddams, Judah Levine
A time scale is a procedure for accurately and continuously marking the passage of time. It is exemplified by coordinated universal time (UTC), and provides the backbone for critical navigation tools such as the global positioning system (GPS). Present

Towards the optical second: verifying optical clocks at the SI limit

April 11, 2019
Author(s)
William F. McGrew, Xiaogang Zhang, Robert J. Fasano, Holly Leopardi, Daniele Nicolodi, Kyle P. Beloy, Jian Yao, Jeffrey A. Sherman, Stefan A. Schaeffer, Joshua J. Savory, Stefania Romisch, Christopher W. Oates, Thomas E. Parker, Tara M. Fortier, Andrew D. Ludlow
The pursuit of ever more precise measures of time and frequency motivates redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on the microwave hyperfine transition in 133Cs, it is

Progress on Optical-clock-based Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

April 20, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

Incorporating an Optical Clock into a Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

March 29, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

Incorporating an Optical Clock into a Time Scale

January 1, 2018
Author(s)
Jian Yao, Thomas E. Parker, Neil Ashby, Judah Levine
This paper discusses how to build a time scale with an intermittently-operated optical clock. In particular, it gives suggestions on how long and how often to run an optical clock. It also explores the benefits of having an optical clock in a time scale

JY1 Time Scale: a New Kalman-Filter Time Scale Designed at NIST

October 17, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a new Kalman-filter Hydrogen-maser time scale (i.e., JY1 time scale) designed at NIST. The JY1 time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, to ease operations with existing data

A Clock Ensemble Using Only Active Hydrogen Masers

January 31, 2017
Author(s)
Thomas E. Parker, Stefania Romisch
The current real-time timescale at NIST, AT1, as well as the post-processed scale TP162, both contain hydrogen masers and commercial cesium frequency standards. The cesium standards are much nosier in the short term than the hydrogen masers and

A Study on Using the SDR Receiver for the Europe-Europe and Transatlantic TWSTFT Links

January 31, 2017
Author(s)
Victor S. Zhang, Thomas E. Parker, Joseph Achkar, Dirk Piester, Yi-Jiun Huang, Shinn-Yan Lin, Zhiheng Jiang
The BIPM and the CCTF Working Group on TWSTFT have stimulated a pilot study on using software defined radio (SDR) receivers for TWSTFT in the framework of the realization of International Atomic Time (TAI). The SDR receivers based on a software developed

Accurate TWSTFT time transfer with indirect links

January 31, 2017
Author(s)
Victor S. Zhang, Zhiheng Jiang, Thomas E. Parker, Jian Yao, Yi-Jiun Huang, Shinn-Yan Lin
The conventional wisdom suggests a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) time link should result in a smaller uncertainty than that of an indirect TW link over the same baseline [12]. This is why all Coordinated Universal Time

The development of a new Kalman-filter time scale at NIST

January 31, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a preliminary design of a new Kalman-filter Hydrogen-maser time scale at NIST. The time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, just for easy operations with the existing data. All

Doppler Sensitivity and Its Effect on Transatlantic TWSTFT Links

December 6, 2016
Author(s)
Shengkang Zhang, Tom Parker, Victor S. Zhang
Two Way Satellite Time and Frequency Transfer (TWSTFT or TW) is a commonly used technique to compare time and frequency precisely among the time and frequency laboratories. The precision of TWSTFT on time comparison is about 0.5 ns or even better, which

A Study on Reducing the Diurnal in the Europe-to-Europe TWSTFT Links.

April 4, 2016
Author(s)
Victor S. Zhang, Thomas E. Parker, Shengkang Zhang
Most of the Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) links exhibit a daily variation (diurnal) on the order of 1 ns in the differences. The stability of TW is degraded by the diurnal. Many studies on the sources of diurnal have been

Precision measurement of the speed of propagation of neutrinos using the MINOS detectors

September 17, 2015
Author(s)
Stefania Romisch, P Adamson, I Anghel, Neil Ashby, A Aurisano, G. Barr, M. Bishai, A. Blake, C. M. Castromonte, S. Childress, M. Christensen, J. A. Coelho, L. Corwin, D. Cronin-Hennessy, J. K. de Jong, A. V. Devan, N. E. Devenish, M. V. Diwan, C. O. Escobar, J. J. Evans, E. Falk, G. J. Feldman, Blair Fonville, M. V. Frohne, H. R. Gallagher, R. A. Gomes, M. C. Goodman, P. Gouffon, N. Graf, R. Gran, K. Grzelak, A. Habig, S. R. Hahn, J. Hartnell, R. Hatcher, Jonathan Hirschauer, A. Holin, J. Huang, J. Hylen, G M. Irwin, Z. isvan, C. James, Steven R. Jefferts, D. Jensen, T. Kafka, S. M. Kasahara, G. Koizumi, M. Kordosky, A. Kreymer, K. Lang, J. Ling, P. J. Litchfield, P. Lucas, W. A. Mann, M. L. Marshak, Demetrios Matsakis, N. Mayer, Angela Mckinley, C. McGivern, M. M. Medeiros, R. Mehdiyev, J Meier, M. D. Messier, W. H. Miller, S. R. Mishra, Stephen Mitchell, S. Moed Sher, C. D. Moore, L. Mualem, J. A. Musser, D. Naples, J. K. Nelson, H. Newman, R. J. Nichol, J. A. Nowak, J. C. O'Conner, M. Orchanian, R. B. Pahlka, J. Paley, Thomas E. Parker, R. B. Patterson, G. Pawloski, A. Perch, S. Phan-Budd, R. K. Plunkett, N. Poonthattatil, Ed Powers, X. Qiu, A. Radovick, B. Rebel, K. Ridl, C. Rosenfeld, H. A. Rubin, M. C. Sanchez, J. Schneps, A. Schreckenberger, P. Schreiner, R. Sharma, A, Sousa, N. Tagg, R, L. Talaga, J. Thomas, M. A. Thomson, X. Tian, A. Timmons, S. C. Tognini, R. Toner, D. Torretta, J. Urheim, P. Vahle, B. Viren, A. Weber, R. C. Webb, C. White, L. Whitehead, L. H. Whitehead, S. G. Wojcicki, J. Wright, Victor S. Zhang, R. Zwaska
We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and

Bias Corrections in Primary Frequency Standards

April 13, 2015
Author(s)
Thomas E. Parker, Thomas P. Heavner, Steven R. Jefferts
Primary frequency standards serve the function of calibrating the rate of International Atomic Time, TAI, and therefore play a critical role in the accuracy of the world's time. The Working Group on Primary and Secondary Frequency Standards, WGPSFS, is an

Long-Term Uncertainty in Time Transfer Using GPS and TWTFT Techniques

April 13, 2015
Author(s)
Victor S. Zhang, Thomas E. Parker, Jian Yao
The techniques of GPS time and frequency transfer (code based and carrier phase) and two-way satellite time and frequency transfer (TWSTFT) are widely used in remote clock comparison and in the computation of International Atomic Time (TAI). Many timing

First Accuracy Evaluation of NIST-F2

May 1, 2014
Author(s)
Thomas P. Heavner, Steven R. Jefferts, Jon H. Shirley, Thomas E. Parker, Elizabeth A. Donley, Neil Ashby, Stephan E. Barlow, Filippo Levi, Giovanni Costanzo
We report the first accuracy evaluation of NIST-F2, a second generation laser-cooled Cesium fountain primary standard developed at NIST with a cryogenic (Liquid Nitrogen) microwave cavity and flight region. The 80 K atom interrogation environment reduces

High-accuracy measurement of the black-body radiation frequency shift of the ground-state hyperfine transition in 133 Cs

February 7, 2014
Author(s)
Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Elizabeth A. Donley, Neil Ashby
We report a high-accuracy direct measurement of the blackbody radiation shift (BBR) of 133Cs ground state hyperfine transition. This frequency shift is one of the largest systematic frequency biases encountered in realizing the current definition of the SI

Three-Corner Hat Analysis of the Stability of UTC and Various UTC(k)s

December 5, 2013
Author(s)
Thomas E. Parker
The stabilities of some local UTC time scales have recently improved dramatically with the increasing use of cesium or rubidium fountains as nearly always present frequency references. Along with time scales using maser ensembles, there are now a number of

A Study of the Diurnal in the Transatlantic TWSTFT Difference

September 7, 2013
Author(s)
Victor S. Zhang, Thomas E. Parker
The daily variation (diurnal) in the two-way satellite time and frequency transfer (TWSTFT) difference is one of the most significant instabilities of the TWSTFT technique. The diurnal comes from the daily delay change of the TWSTFT signal paths. In recent