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Search Publications by: Tom Parker (Assoc)

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Displaying 26 - 50 of 134

Enabling accurate differential calibration of modern GPS receivers

November 26, 2012
Author(s)
Stefania Romisch, Victor S. Zhang, Thomas E. Parker, Steven R. Jefferts
The difference between the local time reference and a GNSS receiver's internal time base is an essential contributor to the calibration of that receiver when used as a timing device. In the past, in the absence of a PPS output signal provided by the

Measurement of the velocity of the neutrino with MINOS

November 26, 2012
Author(s)
Stefania Romisch, P Adamson, Neil Ashby, G. Barr, M. Bishal, A. Blake, G. J. Bock, D. Bogert, Russell Bumgarner, S. V. Cao, S. Childress, M. Christensen, J. Coelho, L. Corwin, D. Cronin-Hennessy, J. K. de Jong, N. E. Devenish, M. V. Diwan, C. O. Escobar, J. J. Evans, E. Falk, G. J. Feldman, C. Flores, Blair Fonville, M. V. Frohne, H. R. Gallager, A. Gavrilenko, R. A. Gomes, P. Gouffon, N. Graf, R. Gran, K. Grzelak, A. Habig, J. Hartnell, R. Hatcher, Jonathan Hirschauer, A. Holin, 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, M. Mathis, Demetrios Matsakis, N. Mayer, Angela Mckinley, M. M. Medeiros, R. Mehdiyev, J. R. Meier, B. Mercurio, M. D. Messier, W. H. Miller, S. R. Mishra, S. Moed Sher, C. D. Moore, L. Mualem, J. A. Musser, J. K. Nelson, H. Newman, R. J. Nichol, J. A. Nowak, J. C. O'Conner, W. P. Oliver, M. Orchanian, R. B. Pahlka, J. Paley, Thomas E. Parker, R. B. Patterson, G. Pawloski, S. PhanBudd, R. K. Plunkett, N. Poonthattatil, Ed Powers, X. Qiu, A. Radovic, B. Rebel, C. Rosenfeld, H. A. Rubin, M. C. Sanchez, J. Schneps, P Schireiner, A. Schreckenberger, R. Sharma, A, Sousa, N. Tagg, R, L. Talaga, J. Thomas, M. A. Thomson, X. Tian, S. C. Tognini, R. Toner, D. Torretta, G. Tzanakos, J. Urheim, P. Vahel, A. Webber, R. C. Webb, C. White, L. H. Whitehead, L. Whitehead, K. P. Wilson, S. G. Wojcicki, J. Wright, Victor S. Zhang, R. Zwaska
The MINOS experiment uses a beam of predominantly muon-type neutrinos generated using protons from the Main Injector at Fermilab in Batavia, IL and travelling 735 km through the Earth to a disused iron mine in Soudan, MN. The 10 us-long beam pulse contains

Recent Calibrations of UTC(NIST) and UTC(USNO)

November 26, 2012
Author(s)
Victor S. Zhang, Thomas E. Parker, Russell Bumgarner, Jonathan Hirschauer, Angela Mckinley, Stephen Mitchell, Ed Powers, Jim Skinner, Demetrios Matsakis
The National Institute of Standards and Technology (NIST) and the United States Naval Observatory (USNO) use GPS common-view, carrier-phase time transfer and Two Way Satellite Time and Frequency Transfer (TWSTFT, also known as TWSTT) techniques in our time

Synchronization between remote sites for the MINOS experiment

November 26, 2012
Author(s)
Stefania Romisch, Steven R. Jefferts, Victor S. Zhang, Thomas E. Parker, Neil Ashby, P Adamson, G. Barr, A. Habig, J Meier, C. James, R. Nicol, R. Plunkett, C. Rosenfeld, Russell Bumgarner, M. Christensen, Jonathan Hirschauer, Blair Fonville, Demetrios Matsakis, Ed Powers, J. Wright, Angela Mckinley
In the context of time-of-flight measurements, the timing at the departure and arrival locations is obviously critical to the outcome of the experiment. In the case of neutrino time-of-flight experiments, the locations are many hundreds of kilometers apart

A digital time scale at the National Institute of Standards and Technology

August 13, 2011
Author(s)
Stefania Romisch, Steven R. Jefferts, Thomas E. Parker
An integrated time scale has as primary data unit of duration (time interval) defined by atomic standards according to the definition of the SI second. The availability of more than one atomic standard allows for averaging, thereby improving the

Comparing Room Temperature and Cryogenic Cesium Fountains

July 31, 2011
Author(s)
Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Elizabeth A. Donley, Filippo Levi, Davide Calonico, C Calosso, Giovanni Costanzo, B. Mongino
We have compared the frequency of a room temperature cesium fountain primary frequency standard with that of a cryogenic (~80K) cesium fountain. This comparison yields a measurement of the blackbody frequency shift of the room temperature fountain.

Towards an all-digital time scale

July 31, 2011
Author(s)
Stefania Romisch, Steven R. Jefferts, Thomas E. Parker
The implementation of an all-digital time scale is under way at NIST, using a novel 8-channel, all-digital phase measurement system based on subsampling techniques. The phase measurement system is used to compare output signals from several commercial

Update on a Comparison of Cesium Fountain Primary Frequency Standards

July 31, 2011
Author(s)
Thomas E. Parker
An update to a previous long term frequency comparison of cesium fountain primary frequency standards has been made. This update covers the approximate three year interval from March 2008 to March 2011 and also includes two new standards. Also, simulated

NIST F1 and F2

November 15, 2010
Author(s)
Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley, Paul D. Kunz, Steven R. Jefferts
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

Medium-Term Frequency Stability of Hydrogen Masers as Measured by a Cesium Fountain

June 2, 2010
Author(s)
Thomas E. Parker, Steven R. Jefferts, Thomas P. Heavner
Abstract Hydrogen masers are used extensively in time scale ensembles, but the frequency drift must be accurately known. NIST-F1, the cesium fountain primary frequency standard at the National Institute of Standards and Technology, now operates nearly

Long-term comparison of caesium fountain primary frequency standards

December 7, 2009
Author(s)
Thomas E. Parker
There are currently nine caesium fountain primary frequency standards regularly reporting calibrations of International Atomic Time to the Bureau International des Poids et Measures (BIPM). An investigation has been carried out using data from the BIPM

Novel, All-Digital Phase Measurement System for Time Scales

November 16, 2009
Author(s)
Stefania Romisch, Thomas E. Parker, Steven R. Jefferts
A novel, all-digital phase measurement system, to be utilized as part of the NIST Time Scale at NIST in Boulder, CO is presented. The system is used to compare output signals from several commercial atomic frequency standards: the phase differences between

Two-Way Satellite Time and Frequency Transfer Using 1 MChip/S codes

November 16, 2009
Author(s)
Victor S. Zhang, Thomas E. Parker, Demetrios Matsakis, Joseph Achkar, Daniele Rovera, Dirk Piester, Andreas Bauch, Luca Lorini
The Ku-band transatlantic and Europe to Europe two-way satellite time and frequency transfer (TWSTFT) operations used the 2.5 MChip/s pseudo-random codes with 3.5 MHz bandwidth until the end of July, 2009. The cost of TWSTFT operation is associated with

A Spin-1/2 Optical Lattice Clock

August 7, 2009
Author(s)
Nathan D. Lemke, Andrew D. Ludlow, Zeb Barber, Tara M. Fortier, Scott A. Diddams, Yanyi Jiang, Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Christopher W. Oates
We experimentally investigate an optical clock based on 171Yb (I = 1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including the density-dependent collision shift, with an uncertainty of 0.19

Frequency Measurements of Al+ and Hg+ Optical Standards

June 8, 2009
Author(s)
Wayne M. Itano, James C. Bergquist, Till P. Rosenband, David J. Wineland, David Hume, Chin-wen Chou, Steven R. Jefferts, Thomas P. Heavner, Tom Parker, Scott Diddams, Tara Fortier
Frequency standards based on narrow optical transitions in 27Al+ and 199Hg+ ions have been developed at NIST. Both standards have absolute reproducibilities of a few parts in 10 17. This is about an order of magnitude better than the fractional uncertainty

Yb Optical Lattice Clock

November 23, 2008
Author(s)
Nathan D. Lemke, Andrew Ludlow, Zeb Barber, N Poli, C.W. Hoyt, Long-Sheng Ma, Jason Stalnaker, Christopher W. Oates, Leo Hollberg, James C. Bergquist, A. Brusch, Tara Fortier, Scott Diddams, Thomas P. Heavner, Steven R. Jefferts, Tom Parker
We describe the development and latest results of an optical lattice clock based on neutral Yb atoms, including investigations based on both even and odd isotopes. We report a fractional frequency uncertainty below 10 -15 for 171Yb.

NIST F1 and F2

October 5, 2008
Author(s)
Thomas P. Heavner, Tom Parker, Jon H. Shirley, Steven R. Jefferts
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. At the time of the last Symposium on Frequency Standards and

Recent atomic clock comparisions at NIST

October 1, 2008
Author(s)
Luca Lorini, Neil Ashby, Anders Brusch, Scott Diddams, Robert E. Drullinger, Eric Eason, Tara Fortier, Pat Hastings, Thomas P. Heavner, David Hume, Wayne M. Itano, Steven R. Jefferts, Nathan R. Newbury, Tom Parker, Till P. Rosenband, Jason Stalnaker, William C. Swann, David J. Wineland, James C. Bergquist
The record of atomic clock frequency comparisons at NIST over the past half-decade provides one of the tightest constraints of any present-day, temporal variations of the fundamental constants. Notably, the 6-year record of increasingly precise

Frequency evaluation of the doubly forbidden 1 S 0 - 3 P 0 transition in bosonic 174 Yb

May 6, 2008
Author(s)
Nicola Poli, Zeb Barber, Nathan D. Lemke, Christopher W. Oates, Tara Fortier, Scott Diddams, Leo W. Hollberg, James C. Bergquist, Anders Brusch, Steven R. Jefferts, Thomas P. Heavner, Tom Parker
We report an uncertainty evaluation of an optical lattice clock based on the 1S 0 – 3P 0 transition in the bosonic isotope 174Yb using magnetically induced spectroscopy. The uncertainty due to systematic effects has been reduced to less than 0.8Hz, which

A Comparison of Cs Fountain Primary Frequency Standards

April 23, 2008
Author(s)
Thomas E. Parker
There are currently 9 cesium fountain primary frequency standards reporting calibrations of TAI to the Bureau International des Poids et Measures (BIPM). An investigation has been carried out using data from the BIPM publication Circular T to evaluate the

Long-term Stability of Remote Clock Comparisons with IGS Clock Products

November 27, 2007
Author(s)
Victor S. Zhang, Thomas E. Parker, Marc A. Weiss
The International GNSS Service (IGS) clock products contain clock information of the local reference for the IGS tracking receivers with respect to the IGS time. The clock information is obtained from GPS carrier-phase measurements. Many timing

Optical-to-microwave frequency comparison with fractional uncertainty of 10 -15

October 1, 2007
Author(s)
Jason Stalnaker, Scott A. Diddams, Tara M. Fortier, K Kim, Leo W. Hollberg, James C. Bergquist, Wayne M. Itano, Marie Delaney, Luca Lorini, Windell Oskay, Thomas P. Heavner, Steven R. Jefferts, Filippo Levi, Thomas E. Parker, Jon H. Shirley
We report the technical aspects of the optical-to-microwave comparison for our recent measurements of the optical frequency of the mercury single-ion frequency standard in terms of the SI second as realized by the NIST-F1 cesium fountain clock. Over the