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NIST Authors in Bold

Displaying 1876 - 1900 of 2516

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.

Coordinating GPS Calibrations Among NIST, NRL, USNO, PTB, and OP

July 31, 2011
Author(s)
Marc A. Weiss, Victor S. Zhang, J White, K Senior, Demetrios Matsakis, S. Mitchell, P Uhrich, D Valat, W Lewandowski, G. Petit, Andreas Bauch, T. Feldman, A. Proia
Reviewing calibration results over the history since early 1980’s among several labs shows very mixed results. The best stabilities of receivers, as given by calibrations, are of the order of a few ns or better over a year, though many results are quite a

Improving the stability and accuracy of the Yb optical lattice clock

July 31, 2011
Author(s)
Andrew D. Ludlow, Yanyi Jiang, Nathan D. Lemke, Jeffrey A. Sherman, J. von Stecher, Richard W. Fox, Long-Sheng Ma, A.M. Rey, Christopher W. Oates
We report results for improving the stability and uncertainty of the NIST $^{171}$Yb lattice clock. The stability improvements derive from a significant reduction of the optical Dick effect, while the uncertainty improvements focus on improved

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

MOT Loading Enhancement with Stimulated Light Forces

July 31, 2011
Author(s)
Elizabeth A. Donley, Tara C. Liebisch, Eric M. Blanshan, John E. Kitching
We demonstrate atom number enhancement in a magneto-optical trap (MOT) by use of bichromatic cooling to slow an atomic beam that is loaded into a MOT. Bichromatic cooling employs stimulated emission to apply strong cooling forces that are not limited by

Residual PM Noise Evaluation of Radio Frequency Mixers

July 31, 2011
Author(s)
Corey A. Barnes, Archita Hati, Craig W. Nelson, David A. Howe
Direct observation of phase modulated (PM) noise is often difficult due to the high dynamic range that exists between the carrier and the modulated sidebands. A common tool used to reduce the dynamic range is the phase detector, which removes the carrier

Status of a compact cold-atom CPT frequency standard

July 31, 2011
Author(s)
Elizabeth A. Donley, Francois-Xavier R. Esnault, John E. Kitching, Eugene N. Ivanov
We describe the main progress towards the realization of a cold atom frequency standard based on coherent population trapping (CPT). We explain our particular CPT configuration and give details on the experimental setup.

Synchronizing Computer Clocks Using Kalman Filters

July 31, 2011
Author(s)
Judah Levine
I have used the Kalman Filter algorithm to improve the link between the Internet Time Servers operated by the National Institute of Standards and Technology (NIST) and the primary atomic clock ensemble in Boulder, which realizes UTC(NIST) and which is used

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

Vibration Sensitivity of Optical Components: A Survey

July 31, 2011
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe
We propose and demonstrate a novel technique to measure the vibration sensitivity of two-port fiber-based optical components. It uses a common-arm counter-propagating frequency-shifted interferometer that cancels the vibration induced phase noise of the

A circular dielectric grating for vertical extraction of single quantum dot emission

July 25, 2011
Author(s)
Marcelo I. Davanco, Matthew T. Rakher, Dieter Schuh, Antonio Badolato, Kartik A. Srinivasan
We demonstrate a suspended circular grating composed of partially etched annular trenches in a thin GaAs membrane, designed for e±cient and moderately broadband ( approx. 5 nm) extraction of emission from single InAs quantum dots. Simulations indicate that

Diamagnetic correction to the 9 Be + ground-state hyperfine constant

July 21, 2011
Author(s)
Nobuyasu Shiga, Wayne M. Itano, John J. Bollinger
We report an experimental determination of the diamagnetic correction to the 9Be + ground state hyperfine constant A. We measured A = −625 008 837.371(11) Hz at a magnetic field B of 4.4609 T. Comparison with previous results, obtained at lower values of B

Timing in Telecommunications Networks

July 20, 2011
Author(s)
Judah Levine
I describe the statistical considerations used to design systems whose clocks are compared using dial-up telephone lines or the Internet to exchange timing informaiton. The comparison is usually used to synchronize the time of a client system to the time

Normal modes of trapped ions in the presence of anharmonic trap potentials

July 19, 2011
Author(s)
Jonathan Home, David Hanneke, John D. Jost, Dietrich Leibfried, David J. Wineland
We theoretically and experimentally examine the effects of anharmonic terms in the trapping potential for linear chains of trapped ions. We concentrate on two different effects, which become significant at different levels of anharmonicity. The first is a

Dimensional Analysis of Through Silicon Vias Using the TSOM Method

July 12, 2011
Author(s)
Ravikiran Attota, Andrew Rudack
There is a great need for accurate, truly-3D metrology solutions that can be used for analysis of high aspect ratio features such as through-silicon-vias (TSVs). Through-focus scanning optical microscopy (TSOM) is an optical metrology method that provides

State Resolved THz Spectroscopy and Dynamics of Crystalline Peptide/Water Systems

July 11, 2011
Author(s)
Zeeshan Ahmed, Shin G. Chou, Karen M. Siegrist, David F. Plusquellic
State resolved THz studies of crystalline peptides and their hydrates have provided precise measures of the infrared active phonon modes that reflect motions on the longest possible length scales in these systems. The impact of co-crystallized water on the

Absolute transition frequencies and quantum interference in a frequency comb based measurement of the 6,7Li D lines

July 6, 2011
Author(s)
Craig J. Sansonetti, Clayton Simien, John D. Gillaspy, Joseph N. Tan, Samuel M. Brewer, Roger C. Brown, Saijun Wu, James V. Porto
Optical frequencies of the D lines of 6,7Li were measured with a relative accuracy of 5x10-11 using an optical comb synthesizer. Quantum interference in the laser induced fluorescence for the partially-resolved D2 lines was found to produce polarization

Generation of Ultrastable microwaves via optical frequency division

June 26, 2011
Author(s)
Tara Fortier, Matthew S. Kirchner, Jennifer A. Taylor, James C. Bergquist, Yanyi Jiang, Andrew Ludlow, Christopher W. Oates, Till P. Rosenband, Scott Diddams, Franklyn Quinlan, Nathan D. Lemke
A frequency-stabilized femtosecond laser optical frequency comb serves as a source of microwave signals having very low close-to-carrier phase noise. Comparison of two independent systems shows combined absolute phase noise of -100 dBc/Hz at an offset of 1
Displaying 1876 - 1900 of 2516
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