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Physics

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Displaying 1551 - 1575 of 2493

A Half Century of Cryogenics and CSA

May 5, 2014
Author(s)
Ray Radebaugh
1964 seems just like yesterday to me, yet it was 50 years ago. The Cryogenic Society of America (CSA) was born that year, and I was just beginning my professional career in cryogenics. Because I have been active in cryogenics for all these past 50 years, I

ATOMIC DATA AND COLLISIONAL-RADIATIVE MODEL FOR BERYLLIUM AND ITS IONS

May 2, 2014
Author(s)
D. Kondratyev, O. Marchuk, Leonid Vainshtein, Igor Bray, Dmitry Fursa, Yuri Ralchenko, D. Fursa
In this work we present a collisional-radiative model constructed for all ionization stages of beryllium. Convergent close-coupling, K-matrix and Coulomb-Born-exchange methods were applied to calculate the necessary atomic data. For neutral beryllium atom

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

WWVB Time Signal Broadcast: A New Enhanced Broadcast Format and Multi-Mode Receiver

May 1, 2014
Author(s)
John P. Lowe, Yingsi Liang, Oren Eliezer, Dinesh Rajan
WWVB is a broadcast station, operated by the National Institute of Standards and Technology, that has been broadcasting time information to radio-controlled clocks (RCC) throughout the continental US since 1965. The transmitted information includes the

Coordinate-space approach to vacuum polarization

April 28, 2014
Author(s)
Peter J. Mohr, P Indelicatio, J. Sapirstein
The vacuum-polarization correction for bound electrons or muons is examined. The objective is to formulate a framework for calculating the correction from bound-state quantum electrodynamics entirely in coordinate space, including the Uehling potential

Time-resolved double-slit interference pattern measurement with entangled photons

April 28, 2014
Author(s)
Lynden K. Shalm, Thomas Jennewein, Kevin Resch, Piotr Kolenderski, Carmelo Scarcella, Kelsey D. Johnsen Johnsen, Deny Hamel, Cahterine Holloway, Simone Tisa, Alberto Tosi
The double-slit experiment strikingly demonstrates the wave-particle duality of quantum objects. In this famous experiment, particles pass one-by-one through a pair of slits and are detected on a distant screen. A distinct wave-like pattern emerges after

Energy Levels And Spectral Lines Of Quadruply Ionized Iron (Fe V)

April 24, 2014
Author(s)
Alexander Kramida
This compilation revises and extends the previously recommended list of energy levels of quadruply ionized iron (Fe V) and provides a comprehensive list of observed spectral lines and transition probabilities in this spectrum. The new level optimization

Sensor Calibration and Characterization to Meet Climate Monitoring Requirements

April 24, 2014
Author(s)
Catherine C. Cooksey, Gerald T. Fraser, Howard W. Yoon
The challenge of detecting small changes in the Earth's climate system over decadal and longer time scales places stringent requirements on environmental monitoring systems. Sensors must be well calibrated and maintain their calibration in challenging

Preparation of nanocomposite plasmonic films made from cellulose nanocrystals or mesoporous silica decorated with unidirectionally aligned gold nanorods

April 11, 2014
Author(s)
Michael Campbell, Qingkun Liu, Aric Sanders, Julian Evans, Ivan I. Smalyukh
Using liquid crystalline self-assembly of cellulose nanocrystals, we achieve long-range alignment of anisotropic metal nanoparticles in colloidal nanocrystal dispersions that are then used to deposit thin structured films with ordering features highly

The hyperfine Paschen-Back Faraday effect

March 26, 2014
Author(s)
Svenja A. Knappe, M.A. Zentile, Rebecca Andrews, L. Weller, C.S. Adams, I.G. Hughes
We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour

Dual-polarization-sensitive kinetic inductance detectors for balloon-borne, sub-millimeter polarimetry

March 20, 2014
Author(s)
James A. Beall, Dan Becker, Justus Brevik, Hsiao-Mei Cho, Gene C. Hilton, Kent D. Irwin, Dale Li, David P. Pappas, Jeffrey L. Van Lanen, Johannes Hubmayr
We are developing arrays of kinetic inductance detectors for sub-millimeter polarimetry that will be deployed on the BLAST balloon-borne instrument. The array is feedhorn-coupled, and each pixel contains two lumped-element kinetic inductance detectors

Optical amplification and pulse interleaving for low noise photonics microwave generation

March 12, 2014
Author(s)
Franklyn J. Quinlan, Frederick N. Baynes, Tara M. Fortier, Qiugui Zhou, Allen Cross, Joe Campbelll, Scott A. Diddams
We investigate the impact of pulse interleaving and optical amplification on the spectral purity of microwave signals generated by photodetecting the pulsed output of an Er:fiber-based optical frequency comb. It is shown that the microwave phase noise

WWVB: A Half Century of Delivering Accurate Frequency and Time by Radio

March 12, 2014
Author(s)
Michael A. Lombardi, Glenn K. Nelson
In commemoration of its 50th anniversary of broadcasting from Fort Collins, Colorado, this paper provides a history of National Institute of Standards and Technology (NIST) radio station WWVB. The narrative describes the evolution of the station, from its

A collapse of the cross-spectral function in phase noise metrology

February 25, 2014
Author(s)
Craig W. Nelson, Archita Hati, David A. Howe
Cross-spectral analysis is a mathematical tool for extracting the power spectral density of a correlated signal from two time series in the presence of uncorrelated interfering signals. We demonstrate and explain a set of conditions where the detection of

Supercontinuum generation in an on-chip silica waveguide

February 13, 2014
Author(s)
Scott A. Diddams, Dong Yoon Oh, David Sell, Hansuek Lee, Ki Youl Yang, Kerry J. Vahala
Supercontinuum generation is demonstrated in an on-chip silica spiral waveguide by launching 180-fs pulses from an optical parametric oscillator at the center wavelength 1330 nm. With a coupled pulse energy of 2.17 nJ, the broadest spectrum in the

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

Frequency Measurement

February 3, 2014
Author(s)
Michael A. Lombardi
An overview of frequency metrology, with emphasis on estimating accuracy and stability, oscillator types, and measurement instrumentation. It describes how to measure frequency and the statistics and terminology that are used to report the results. The

Head and Media Challenges for 3 Tb/in 2 Microwave Assisted Magnetic Recording

February 3, 2014
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Mike Mallary, Kumar Srinivasan, Gerado Bertero, Dan Wolf, Christian Kaiser, Michael Chaplin, Mahendra Pakala, Leng Qunwen, Yiming Wang, Carl Elliot, Lui Francis
A specific design for Microwave Assisted Magnetic Recording (MAMR) at about 3Tb/in 2 (0.47 Tb/cm 2 or 4.7 Pb/m 2) is discussed in detail to highlight the challenges of MAMR and to contrast its requirements with conventional Perpendicular Magnetic Recording
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