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Search Publications by: Neil Ashby (Assoc)

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Displaying 26 - 50 of 102

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

Why there is no noon-midnight red shift in the GPS

July 24, 2013
Author(s)
Neil Ashby, Marc A. Weiss
Although the effects of solar and lunar gravitational potentials on the frequencies of orbiting GPS clocks are actually negligible, a naive calculation appears to show that such effects are significant, depending on whether the SV clock is between 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

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

Calibration uncertainty for the NIST PM/AM noise standards

July 31, 2012
Author(s)
Archita Hati, Craig W. Nelson, Neil Ashby, David A. Howe
NIST provides an on-site calibration service of the accuracy of phase modulation (PM) noise, amplitude modulation (AM) noise and noise floor of the measurement systems at a customer's site using one or more portable PM/AM secondary noise standards. In this

Characterizing Dynamic Effects of Oscillator Power Cycling

November 14, 2011
Author(s)
David A. Howe, Danielle G. Lirette, Neil Ashby, Archita Hati, Craig W. Nelson
We create a measurement technique and metrics consistent with easy interpretation to be used in development of new oscillators specifically for applications in which the oscillator’s power is turned on and off. This is useful in predicting the performance

A Laser-Cooled Frequency Standard for GPS

September 20, 2011
Author(s)
Thomas P. Heavner, Stephan E. Barlow, Marc A. Weiss, Neil Ashby, Steven R. Jefferts
NIST is in an initial phase of developing a prototype laser-cooled atomic frequency standard (AFS) for potential use in a future GPS system. The expected fractional frequency stability or Allan deviation, ς y(τ), will be 2x10 -13 at one second, improving

Limited Live-time Measurements of Frequency Spectra

July 31, 2011
Author(s)
David A. Howe, Neil Ashby, Danielle G. Lirette, Archita Hati, Craig W. Nelson
Frequency-difference-of-arrival (FDOA) can be used to monitor and track an emitter’s location by observing Doppler frequency shifts of the carrier during short pulsed transmissions. This specific application needs to consider two frequency-stability levels

Accurate light-time correction due to a gravitating mass

June 7, 2010
Author(s)
Neil Ashby, Bruno Bertotti
This technical paper of mathematical physics arose as an aftermath of the 2002 Cassini experiment, in which the PPN parameter γ was measured with an accuracy ς γ = 2.3 × 10 -5 and found consistent with the rediction γ=1 of general relativity. The Orbit