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Physics

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Displaying 1501 - 1525 of 2516

PM Noise Measurement at W-Band

December 12, 2014
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe
We present improved performance for a 92 - 96 GHz cross-spectrum phase modulated (PM) noise measurement system previously reported. The system is principally designed to measure amplifiers in pulsed mode with a duty cycle of 10% to 100% (CW) at a given

Experimental Bounds on Classical Random Field Theories

December 10, 2014
Author(s)
Joffrey K. Peters, Sergey V. Polyakov, Jingyun Fan, Alan L. Migdall
Alternative theories to quantum mechanics motivate important fundamental tests of our understanding and description of the smallest physical systems. Here we place experimental limits on those classical field theories which result in power-dependent

GPS Measurements Anomaly and Continuous GPS Carrier-Phase Time Transfer

December 4, 2014
Author(s)
Jian Yao, Judah Levine
The wide application of GPS carrier-phase (CP) time transfer is limited by the problem of boundary discontinuity (BD). The discontinuity has two categories. One is "day boundary discontinuity", which has been studied a lot and can be solved by a few

International Comparisons of Network Time Protocol Servers

December 4, 2014
Author(s)
Michael A. Lombardi, Judah Levine, Jose M. Lopez, Francisco Jimenez, John Bernard, Marina Gertsvolf, Harold Sanchez, Oscar G. Fallas, Liz C. Hernandez Ferero, Ricardo de Carvalho, Mario Fittipaldi, Raul Solis, Franklin Espejo
This paper describes a recently designed system that measures the time transmitted by network time protocol (NTP) servers located in North, Central, and South America. Direct measurements of the time transmitted by each server are obtained by comparing the

Measured Ionosphere Delay Correction for Code-Based GPS Time Transfer

December 4, 2014
Author(s)
Victor S. Zhang, Zhiqi Li
Nowadays, more and more dual-frequency, multichannel receivers are used in GPS time and frequency transfer applications. Instead of using the modeled ionosphere delay correction or using the IGS ionospheric map, we can obtain the ionosphere delay

Electron and Hole Photoemission Detection for Band Offset Determination of Tunnel Field-Effect Transistor Heterojunctions

November 24, 2014
Author(s)
Wei Li, Qin Zhang, R. Bijesh, Oleg A. Kirillov, Yiran Liang, Igor Levin, Lianmao Peng, Xuelei Liang, S. Datta, David J. Gundlach, Nhan V. Nguyen
The electrical performance of a tunnel field-effect transistor depends critically on the band offset at their semiconductor heterojunction interface. Historically, it has been difficult to experimentally determine how the electronic bands align at the

Quantum engineering of atomic phase shifts in optical clocks

November 24, 2014
Author(s)
Andrew D. Ludlow, T Zanon-willette, S. Almonacil, E. de Clercq, Ennio Arimondo
Quantum engineering of time-separated Raman laser pulses in three-level systems is presented to produce an ultra-narrow, optical-clock transition free from light shifts and with a significantly reduced sensitivity to laser parameter fluctuations. Based on

IR-enhanced Si reference detectors for 1-step scale transfers from 300 nm to 1000 nm

November 20, 2014
Author(s)
George P. Eppeldauer, Thomas C. Larason, Jeanne M. Houston, Robert E. Vest, Uwe Arp, Howard W. Yoon
IR-enhanced Si photodiodes have improved radiometric and electronic characteristics as compared to other widely used Si photodiodes and can be used as responsivity standards in the wavelength range from 300 nm to 1000 nm. Their low predicted uncertainty

Broadband Noise Limit in the Photodetection of Ultralow Jitter Optical Pulses

November 14, 2014
Author(s)
Franklyn J. Quinlan, W. Sun, Tara M. Fortier, Jean-Daniel Deschenes, Yang Fu, Scott A. Diddams, Joe Campbell
Applications with optical atomic clocks and precision timing often require the transfer of optical frequency references to the electrical domain with extremely high fidelity. Here we examine the impact of photocarrier scattering and distributed absorption

Measurement and Calculation of Absolute Single and Double Charge Exchange Cross Sections for O6+ Ions at 1.17 keV/u and 2.33 keV/u Impacting He and H2

November 10, 2014
Author(s)
J. R. Machacek, D. P. Mahapatra, D. R. Schultz, Yuri Ralchenko, A. Chutjian, J. Simcic, S. M. Madzunkov, R. J. Mawhorter
Absolute single and double charge-exchange (CE) cross sections for the astrophysically-prominent O6+ ion with the atomic and molecular targets He and H2 are reported. These collisions give rise to X-ray emissions in the interplanetary medium, planetary

A Low-Cost Time Transfer Receiver for Contributions to Coordinated Universal Time

November 6, 2014
Author(s)
Michael A. Lombardi, Andrew N. Novick, Victor S. Zhang
This paper describes a low-cost time transfer receiver that allows timing laboratories, including national metrology institutes and other designated institutions, to contribute data to the computation of Coordinated Universal Time (UTC). The time transfer

Fast transport of mixed-species ion chains within a Paul trap

November 6, 2014
Author(s)
Ryan S. Bowler, M. Palmer, John P. Gaebler, Dietrich G. Leibfried, J. G. Ceremuga
We investigate the dynamics of mixed-species ion crystals during transport between spatially distinct locations in a linear Paul trap in the diabatic regime. In a general mixed-species crystal, all degrees of freedom along the direction of transport are

Frequency Comb Generation in Superconducting Resonators

October 30, 2014
Author(s)
Robert P. Erickson, Michael Vissers, Martin O. Sandberg, Steven R. Jefferts, David P. Pappas
We have generated frequency combs spanning 0.5 to 20 GHz in superconducting λ=2 resonators at T ¼ 3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical

Extended and Revised Analysis of Singly Ionized Tin: Sn II

October 28, 2014
Author(s)
K. Haris, Alexander Kramida, A. Tauheed
The electronic structure of singly ionized tin (Sn II) is partly a one-electron and partly a three-electron system with ground configuration 5s25p. The excited configurations are of the type 5s2nℓ in the one-electron part, and 5s5p2, 5p3 and 5s5pnℓ (nℓ =

A Cross-Benchmarking and Validation Initiative for Tokamak 3D Equilibrium Calculations

October 27, 2014
Author(s)
Geoffrey B. McFadden, Allan Reiman, Antoine Cerfon, E. Lazarus, S. Lazerson
We are pursuing a cross-benchmarking and validation initiative for tokamak 3D equilibrium calculations, with 11 codes participating: the linearized tokamak equilibrium codes IPEC and MARS-F,the time-dependent extended MHD codes M3D-C1, M3D, and NIMROD, the

Magnetoencephalography of Epilepsy with a Microfabricated Atomic Magnetrode

October 22, 2014
Author(s)
Svenja A. Knappe, Orang Alem, Alex M. Benison, Daniel S. Barth, John E. Kitching
We measured the magnetic signature of epileptiform discharges with high signal-to-noise ratio, using microfabricated atomic magnetometers based on laser spectroscopy of rubidium vapor and similar in size to scalp EEG electrodes. Sensitivity to neuronal

A geometric description of nonreciprocity in coupled two-mode systems

October 16, 2014
Author(s)
Leonardo M. Ranzani, Jose A. Aumentado
We explore the concept of nonreciprocity in coupled two-mode systems using a geometric mapping to the Poincaré sphere. From this perspective, we recast the requirements for nonreciprocity in terms of rotation and inversion symmetry arguments for the vector

Challenges of Irradiance-mode Spectral Response Measurements

October 16, 2014
Author(s)
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Howard W. Yoon
Irradiance-mode spectral response measurements of solar cells are important because they provide a direct, reliable and accurate route for determination of the short circuit current (Isc) of solar cells under air mass 1.5 standard reference spectrum. In

High-Power and High-Linearity Photodetector Modules for Microwave Photonic Applications

October 15, 2014
Author(s)
Frederick N. Baynes, Efthymios Rouvalis, Xiaojun Xie, Qiugui Zhou, Franklyn J. Quinlan, Tara M. Fortier, Scott A. Diddams, Andreas G. Steffan, Andreas Beling, Joe C. Campbell
We demonstrate hermetically packaged InGaAs/InP photodetector modules for high performance microwave photonic applications. The devices employ an advanced photodiode epitaxial layer known as the modified uni-traveling carrier photodiode (MUTC-PD) with
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