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Displaying 23076 - 23100 of 73741

Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic Trapped-Ion Crystal Using Entanglement

May 25, 2012
Author(s)
Brian C. Sawyer, Joseph W. Britton, Adam Keith, C.-C Joseph Wang, James K. Freericks, Hermann Uys, Michael Biercuk, John J. Bollinger
We demonstrate a method of sensitive detection and thermometry of individual modes in cold ( sim1 mK), planar one-component ion plasmas. Exploiting precise control over the valence electron spins of several hundred crystallized 9Be + confined in a Penning

A Compact Cold-Atom Frequency Standard Based on Coherent Population Trapping

May 24, 2012
Author(s)
Francois-Xavier R. Esnault, John Kitching, Elizabeth Donley
We present the status of our cold-atom clock based on coherent population trapping, including the present clock stability and a preliminary evaluation of the three main systematic frequency shifts: the 1st-order Doppler shift, the Zeeman shift, and the

A high stability optical frequency reference based on thermal calcium atoms

May 24, 2012
Author(s)
Richard W. Fox, Jeffrey Sherman, W. Douglas, Judith B. Olson, Andrew Ludlow, Christopher W. Oates
Here we report an imprecision below 10 -14 with a simple, compact optical frequency standard based upon thermal calcium atoms. Using a Ramsey-Borde spectrometer we excite features with linewidths 5 kHz for the 1S 0- 3P 1 intercombination line at 657 nm

A hybrid 10 GHz photonic-microwave oscillator with sub-femtosecond absolute timing jitter

May 24, 2012
Author(s)
Tara M. Fortier, Craig W. Nelson, Archita Hati, Franklyn J. Quinlan, Jennifer A. Taylor, Haifeng (. Jiang, Chin-Wen Chou, Nathan D. Lemke, Andrew D. Ludlow, David A. Howe, Christopher W. Oates, Scott A. Diddams
We demonstrate a 10 GHz hybrid oscillator comprised of a phase stabilized optical frequency comb divider and a room temperature dielectric sapphire oscillator. Characterization of the 10 GHz microwave signal via comparison of two independent hybrid

A new algorithm for clock weights for the SIM time scale

May 24, 2012
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, E. de Carlos-Lopez
A time and frequency comparison system has been developed for the Sistema Interamericano de Metrologia (SIM) region in order to compare in real time the time references maintained at the SIM national metrology institutes (NMIs). Since January 2010 a

A Review of Test Artifacts for Additive Manufacturing

May 24, 2012
Author(s)
Shawn P. Moylan, April L. Cooke, Kevin K. Jurrens, John A. Slotwinski, M A. Donmez
A standardized test part can be used to quantitatively evaluate the performance of a machine or process. This document reviews existing test artifacts used to characterize additive processes that are reported in the literature. Several aspects of the test

A Sub-Sampling Digital PM/AM Noise Measurement System

May 24, 2012
Author(s)
Craig W. Nelson, David A. Howe
A digital phase/amplitude modulation (PM/AM) noise measurement system (DNMS) implementing field programmable gate array (FPGA) based digital down converters (DDCs), and 250 MHz analog to digital converters (ADCs) is reported. Performance in the first

Blackbody effects in the Yb optical lattice clock

May 24, 2012
Author(s)
Andrew D. Ludlow, Jeffrey A. Sherman, Nathan D. Lemke, Kyle P. Beloy, Nathan M. Hinkley, M. Pizzocaro, Richard W. Fox, Christopher W. Oates
We report a high accuracy measurement of the differential static polarizability for the clock transition in a Yb lattice clock, a key parameter for determining the blackbody BBR) shift of this transition. We further report efforts to determine the 6s5d3D1

Common-Arm Counter Propagating Phase Bridge for Vibration Sensitivity Measurement

May 24, 2012
Author(s)
Danielle G. Lirette, Corey A. Barnes, Archita Hati, Jason A. DeSalvo, Craig W. Nelson, David A. Howe
Current methods for measuring the vibration sensitivity of microwave devices are primarily limited by choice of cables connecting a stationary platform to a vibrating actuator. We experimentally compare the current ("conventional") method with a new (

Exotic behavior in quantum dot mode-locked lasers: dark pulses and bistability

May 24, 2012
Author(s)
Kevin L. Silverman, Mingming M. Feng, Richard P. Mirin, Steven T. Cundiff
Passively mode-locked semiconductor lasers with self-assembled quantum dot active regions can be operated in exotic output modes, stabilized by the complex gain and absorption dynamics inherent in these structures. One such device emits dark pulses - sharp

Formation of optical flux lattices for ultra cold atoms

May 24, 2012
Author(s)
Ian B. Spielman, Gediminas Juzeliunas
We explore the optical flux lattices produced for ultra-cold atoms in the radiation field when both the atom-light coupling and the detuning exhibit an oscillatory behavior. We analyze not only the magnetic flux but also the geometric vector potential

Investigation Plan - National Institute of Standards and Technology (NIST) Technical Investigation of Building and Emergency Communications System Performance in the Joplin, Missouri, Tornado of May 22, 2011

May 24, 2012
Author(s)
Marc L. Levitan, Long T. Phan, Erica D. Kuligowski, Franklin T. Lombardo, David P. Jorgensen
Following the May 22, 2011 tornado that devastated the City of Joplin, NIST sent four engineers to Missouri on May 24 through May 28 to conduct a preliminary reconnaissance. Based on analysis of the data collected and other criteria required by law and

Mechanical stabilization of a microrod-resonator optical frequency

May 24, 2012
Author(s)
Scott B. Papp, Pascal P. Del'Haye, Scott A. Diddams
We present line-spacing frequency control of a microresonator-based optical frequency comb by way of mechanical actuation. Using this novel technique we have achieved a record level of residual stability in the line spacing of 5 × 10 -15 for 1s averaging

Phase-Noise Measurement of a 670 GHz Source

May 24, 2012
Author(s)
Jason A. DeSalvo, Archita Hati, Craig W. Nelson, David A. Howe
We present phase-noise measurements in support of terahertz electronics. Using digital phase-noise measurement techniques and an even-harmonic mixer, we achieve a phase-noise measurement system in waveguide (WR1.5). At 670 GHz an upper bound of this system

PM-AM Correlation Measurements and Analysis

May 24, 2012
Author(s)
David A. Howe, Archita Hati, Craig W. Nelson, Danielle G. Lirette
We measure and analyze effects of nonlinear mixing of phase-noise modulation (PM) and amplitude-noise modulation (AM) in an oscillating signal by real-time correlations measured in the cross power spectral density (CPSD). We outline sensitive measurements

Ultra-low-noise Regenerative Frequency Divider for High Spectral Purity RF Signal Generation

May 24, 2012
Author(s)
Archita Hati, Craig W. Nelson, Corey A. Barnes, Danielle G. Lirette, Jason A. DeSalvo, Tara M. Fortier, Franklyn J. Quinlan, Andrew D. Ludlow, Till P. Rosenband, Scott A. Diddams, David A. Howe
We implement an ultra-low-noise frequency divider chain from 8 GHz to 5 MHz that utilizes custom-built regenerative frequency divide-by-2 circuits. The single-sideband (SSB) residual phase noise of this regenerative divider at 5 MHz output is -163 dBc/Hz

Vibrational analysis of stabilized lasers

May 24, 2012
Author(s)
Kenneth J. Hughes, Archita Hati, Craig W. Nelson, David A. Howe
Frequency-stabilized lasers are routinely used in a variety of research and application areas relating to laser-cooled atoms. Important applications in the cold-atom regime include atomic time keeping, inertial navigation, gravitational sensing, and

A Case Study of 3D Imaging Productivity Needs to Support Infrastructure Construction

May 23, 2012
Author(s)
Gabriel Dadi, Paul Goodrum, Kamel Saidi, Christopher U. Brown, Joseph Betit
The national infrastructure system is at a crossroads with a need for renewal and expansion in the most efficient manner possible. Light railway construction requires the installation of embedments in reinforced concrete pavement along the length of

Image-based 3D Mapping of Rebar Location for Automated Assessment of Safe Drilling Areas Prior to Placing Embedments in Concrete Bridge Decks

May 23, 2012
Author(s)
Mani Golparvar-Fard, Behshad Ghadimi, Kamel Saidi, Geraldine Cheok, Marek Franaszek, Robert R. Lipman
This paper presents a new image-based approach for 3D mapping the locations of the rebar and embedded components in a railway bridge deck prior to placement of concrete. Our approach enables practitioners to quickly and automatically identify where the
Displaying 23076 - 23100 of 73741
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