U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Physics

Search Publications

Search Title, Abstract, Conference, Citation, Keyword or Author
  • Published Date
Displaying 1226 - 1250 of 2516

Accurate TWSTFT time transfer with indirect links

January 31, 2017
Author(s)
Victor S. Zhang, Zhiheng Jiang, Thomas E. Parker, Jian Yao, Yi-Jiun Huang, Shinn-Yan Lin
The conventional wisdom suggests a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) time link should result in a smaller uncertainty than that of an indirect TW link over the same baseline [12]. This is why all Coordinated Universal Time

Local Distribution and Calibration of Timing Signals at NIST

January 31, 2017
Author(s)
Joshua J. Savory, Liz C. Forero, Kristopher Maurer, Stefania Romisch
The National Institute of Standards and Technology (NIST) timescale produces a real-time realization of UTC(NIST) in the form of a pulse-per-second (PPS) time signal and a 5 MHz frequency reference. The timing signals are distributed to the international

Long-term instability in UTC time links

January 31, 2017
Author(s)
Victor S. Zhang, Demetrios Matsakis, Zhiheng Jiang
Calibration and link stability are the key issues for the UTC time transfer. This study is made in the framework of a joint task group of the CCTF Working Group on TWSTFT and Working Group on GNSS Time Transfer to investigate the long-term instability of

The development of a new Kalman-filter time scale at NIST

January 31, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a preliminary design of a new Kalman-filter Hydrogen-maser time scale at NIST. The time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, just for easy operations with the existing data. All

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Trapped-ion optical atomic clocks at the quantum limits

January 31, 2017
Author(s)
David R. Leibrandt, Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, David B. Hume, David J. Wineland, Chin-Wen Chou
Frequency and its inverse, time, are the most accurately measured quantities. Historically, improvements in the accuracy of clocks have enabled advances in navigation, communication, and science. Since 1967, the definition of the SI second has been based

A New Generation of Magnetoencephalography: Room Temperature Measurements using Optically-Pumped Magnetometers

January 25, 2017
Author(s)
Elena Boto, Sofie S. Meyer, Vishal Shah, Orang Alem, Svenja A. Knappe, Peter Kruger, Mark Fromhold, Peter G. Morris, Richard W. Bowtell, Gareth R. Barnes, Matthew J. Brookes, Mark Lim
Significant advances in the field of quantum sensing mean that magnetic field detectors, operating at room temperature, are now able to achieve sensitivity similar to that of cryogenically cooled devices (SQUIDs). This means that room temperature

A microfabricated optically-pumped magnetic gradiometer

January 18, 2017
Author(s)
Abigail R. Perry, Sean P. Krzyzewski, John E. Kitching, S. Geller, Sheng D., Svenja A. Knappe
We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, with a length of 60 mm and a cross section diameter of 12 mm, is made of two chip-scale atomic

Coherent UV-to-Visible Light Arrays

January 9, 2017
Author(s)
Dong Yoon Oh, Scott Diddams, Ki Youl Yang, Kerry J. Vahala, Connor Fredrick, Gabriel Ycas
Short duration, intense pulses of light can experience dramatic spectral broadening when propagating through lengths of optical fiber. This continuum generation process is caused by a combination of nonlinear optical effects including the formation of so

Preflight Radiometric Calibration of Orbiting Carbon Observatory 2

January 9, 2017
Author(s)
Stephen Maxwell, B. Carol Johnson, Robert Rosenberg, Lars Chapsky, Richard A. Lee, Randy Pollock
This paper describes the prelaunch radiometric calibration of the imaging spectrometers used on the second Orbiting Carbon Observatory (OCO-2). The gain and dark response were characterized for each focal plane array detector element. An integrating sphere

Ultra-stable optical clock with two cold-atom ensembles

January 1, 2017
Author(s)
Marco Schioppo, Roger Brown, Will McGrew, Nathan M. Hinkley, Robert J. Fasano, Kyle Beloy, Gianmaria Milani, Daniele Nicolodi, Jeffrey Sherman, Nate B. Phillips, Christopher W. Oates, Andrew Ludlow
Atomic clocks based on optical transitions are the most stable, and therefore precise, timekeepers available. These clocks operate by alternating intervals of atomic interrogation with ‘dead' time required for quantum state preparation and readout. This

Stoner vs. Heisenberg: Ultrafast exchange reduction and magnon generation during laser-induced demagnetization

December 28, 2016
Author(s)
Thomas J. Silva, Hans T. Nembach, Justin M. Shaw, Emrah Turgut, Dmitriy Zusin, Dominik Legut, Karel Carva, Ronny Knut, Cong Chen, Zhensheng Tao, Stefan Mathias, Martin Aeschlimann, Peter Oppeneer, Henry Kapteyn, Margaret Murnane, Patrik Grychtol
Understanding how the electronic band structure of a ferromagnetic material is modified during laser-induced demagnetization on femtosecond timescales has been a long-standing question in condensed matter physics. Here, we use ultrafast high harmonics to

Adaptive Terahertz Dual Frequency Comb Spectrometer

December 26, 2016
Author(s)
Flavio Caldas da Cruz, Francisco S. Vieira, David F. Plusquellic, Scott A. Diddams
Terahertz dual frequency comb spectroscopy (THz-DFCS) yields high spectral resolution without compromising bandwidth. Nonetheless, the resolution of THz-DFCS is usually limited by the laser repetition rate, which is typically between 80 MHz and 1 GHz. In

Generalized entropy theory of glass-formation in fully flexible polymer melts

December 21, 2016
Author(s)
Jack F. Douglas, Wensheng Xu, Karl Freed
The generalized entropy theory (GET) offers many insights into how molecular parameters influence polymer glass-formation. Given the fact that chain rigidity often plays a critical role in understanding the glass- formation of polymer materials, the GET

Spectral dependence of carrier lifetimes in silicon for photovoltaic applications

December 21, 2016
Author(s)
John F. Roller, Yu-Tai Li, Mario Dagenais, Behrang H. Hamadani
Charge carrier lifetimes in photovoltaic-grade silicon wafers were measured by a spectral-dependent, quasi-steady-state photoconductance technique. Narrow bandwidth LEDs were used to excite excess charge carriers within the material, and the effective

Entropy Theory of Polymer Glass-Formation in Variable Spatial Dimension

December 20, 2016
Author(s)
Jack F. Douglas, Wensheng Xu, Karl Freed
The importance of packing frustration is broadly appreciated to be an important aspect of glass formation. Recently, great interest has focused on probing the dependence on spatial dimension d as a theoretical tool for exploring essential aspects of glass

A Versatile Technique to Enable Sub-Milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-Zone Planet Finder

December 16, 2016
Author(s)
Ryan C. Terrien, Guomundur K. Stefansson, Fred Hearty, Paul Robertson, Suvrath Mahadevan, Tyler Anderson, Chad Bender, Matthew Nelson, Andrew Monson, Basil Blank, Samuel Halverson, Chuck Henderson, Lawrence Ramsey, Arpita Roy, Christian Schwab
Insufficient instrument thermo-mechanical stability is one of the fundamental roadblocks for achieving 10 cm s −1 Doppler radial velocity (RV) precision, the precision needed to detect Earth-twins orbiting Solar-type stars. Exquisite temperature and
Was this page helpful?