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Physics

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Displaying 2101 - 2125 of 2574

Comparison of the NIST and PTB Standards for Air Kerma and Low-Energy X-rays

December 31, 2009
Author(s)
C M. O'Brien, L. Buermann
A comparison has been made of the air-kerma standards for low-energy x-rays at the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). The comparison involved a series of measurements at the PTB and

Radiochromic Film

December 31, 2009
Author(s)
Christopher G. Soares, Sameul Trichter, Slobodan Devic
Media that turns color upon being irradiated (coloration detectors) were some of the earliest available detectors for ionizing radiation. Besides conventional silver halide photographic media, which aided in the discovery of x-rays by Rontgen, barium

Progress Toward Corrugated Feed Horn Arrays in Silicon

December 16, 2009
Author(s)
Joseph W. Britton, Ki W. Yoon, James A. Beall, Daniel T. Becker, Hsiao-Mei Cho, Gene C. Hilton, Michael D. Niemack, Kent D. Irwin
We are developing monolithic arrays of corrugated feed horns fabricated in silicon for dual-polarization single mode operation at 90, 145 and 220 GHz. The arrays consist of hundreds of platelet feed horns assembled from gold coated stacks of micromachined

Compensation of Field-Induced Frequency Shifts in Ramsey Spectroscopy of Optical Clock Transitions

December 10, 2009
Author(s)
A. V. Taichenachev, V. I. Yudin, Christopher W. Oates, Barber W. Zeb, Nathan D. Lemke, Andrew Ludlow, U Sterr, Ch. Lisdat, F Reihle
We develop a modified version of Ramsey spectroscopy that uses an additional frequency shift to compensate frequency shifts induced by the excitation itself. In its simplest realization, this method uses a small step of the probe frequency during the two

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

Extension of the resonance line series of Mg III

December 1, 2009
Author(s)
C M. Brown, Alexander Kramida, Uri Feldman, Joseph Reader
Spectra of Mg emitted by a Penning discharge were recorded in the extreme ultraviolet (EUV) on a 10.7-m grazing-incidence spectrograph with phosphor image plates. The spectra provided nine new lines of Mg III between 156 and 166 Å and allowed us to improve

Ultra-Sensitive Optical Measurements of High-J Transitions in the O2 A-band

November 24, 2009
Author(s)
Daniel K. Havey, Joseph T. Hodges, David A. Long, Mitchio Okumura, Charles E. Miller
We report frequency-stabilized cavity ring-down spectroscopy measurements of high-J O2 A-band magnetic dipole line parameters. Our goals were to measure intensities and line shape parameters for the primary isotopologue of O2 in the A-band region and to

Limits on GPS Carrier Phase Time Transfer

November 16, 2009
Author(s)
Marc A. Weiss
The stability of differential delays between Global Navigation Satellite receivers is critical for time and frequency transfer. We study the limit of this transfer between two specific receivers from the study of data taken from these receivers while they

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

Phase-lock Loops in Vibration Environments

November 16, 2009
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe
A popular scheme for achieving low phase noise across a large range of offset frequencies is to employ an oscillator at an output frequency with low far-from-carrier noise that is phase-locked to a reference that has low close-to-carrier noise. We

Progress on a Portable Rubidium Fountain Frequency Standard

November 16, 2009
Author(s)
Paul D. Kunz, Thomas P. Heavner, Steven R. Jefferts
We are developing a transportable laser-cooled rubidium (Rb) atomic fountain frequency standard. We have a complete optical package, and have recently shown cooled, launched, and detected atoms. Additionally, a new physics package has been designed and is

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

Realization of a programmable two-qubit quantum processor

November 15, 2009
Author(s)
David Hanneke, Jonathan Home, John D. Jost, Jason Amini, Dietrich G. Leibfried, David J. Wineland
The universal quantum computer is a device that could simulate any physical system and represents a major goal for the field of quantum information science. Algorithms performed on such a device are predicted to offer significant gains for some important

Optical frequency stabilization of a 10 GHz Ti:sapphire frequency comb by saturated absorption spectroscopy in 87Rubidium

November 4, 2009
Author(s)
Dirk Heinecke, Albrecht Bartels, Tara M. Fortier, Danielle Braje, Leo Hollberg, Scott A. Diddams
The high power per mode of a recently-developed 10 GHz femtosecond Ti:sapphire frequency comb permits nonlinear Doppler-free saturation spectroscopy in 87Rubidium with a single mode of the comb. We use this access to the natural linewidth of the Rubidium

Preparation of Dicke States in an Ion Chain

November 2, 2009
Author(s)
David Hume, Chin-Wen Chou, Till P. Rosenband, David J. Wineland
We have investigated theoretically and experimentally a method for preparing Dicke states in trapped atomic ions. We consider a linear chain of N ion qubits that is prepared in a particular Fock state of motion, jmi. The m phonons are removed by applying a

A Novel Wafer-plane Dosimeter for EUV Lithography

November 1, 2009
Author(s)
Steven E. Grantham, Charles S. Tarrio
Extreme Ultraviolet Lithography (EUVL) incorporates 13.5 nm light for patterning wafers and requires in-situ wafer-plane dosimetry that can be tailored to the requirements of an EUVL stepper’s environment. There are several types of detectors that are

10-GHz Self-Referenced Optical Frequency Comb

October 30, 2009
Author(s)
Albrecht Bartels, Dirk Heinecke, Scott Diddams
For a decade the femtosecond laser based frequency comb has played a key role in high precision optical frequency metrology.While often referred to as a precise optical frequency ruler, its tick marks are in fact too densely spaced for direct observation

Quantum walk on a line for a trapped ion

October 30, 2009
Author(s)
Peng Xue, Barry Sanders, Dietrich Leibfried
We show how a quantum walk can be experimentally realized for a single trapped ion and how to interpolate between the quantum and random walk by randomizing the phase of a generalized Hadamard coin flip. The signature of the quantum walk is manifested not

Effect of Surface Modes on Photon Propagation through Dielectric Bandgaps

October 28, 2009
Author(s)
Natalia Malkova, Sergey V. Polyakov, Alan L. Migdall, Garnett W. Bryant
We investigate the Hartman saturation effect of photons traveling through barriers created by bandgaps of multilayer stacks. In particular, we investigate theoretically the recently observed jumps in photon transversal times due to adding a single layer
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