Multistart Spiral Electron Vortices In Ionization By Circularly Polarized Uv Pulses,
2016
University of Nebraska-Lincoln
Multistart Spiral Electron Vortices In Ionization By Circularly Polarized Uv Pulses, Jean Marcel Ngoko Djiokap, Alexei V. Meremianin, N. L. Manakov, S. X. Hu, L. B. Madsen, Anthony F. Starace
Anthony F. Starace Publications
Multistart spiral vortex patterns are predicted for the electron momentum distributions in the polarization plane following ionization of the helium atom by two time-delayed circularly polarized ultrashort laser pulses. For two ultraviolet (UV) pulses having the same frequency (such that two photons are required for ionization), single-color two-photon interferometry with corotating or counter-rotating time-delayed pulses is found to lead respectively to zero-start or four-start spiral vortex patterns in the ionized electron momentum distributions in the polarization plane. In contrast, two-color one-photon plus two-photon interferometry with time-delayed corotating or counter-rotating UV pulses is found to lead respectively to one …
Power And Langmuir Probe Measurements Of H2 Rf Plasma,
2016
Macalester College
Power And Langmuir Probe Measurements Of H2 Rf Plasma, Alexander A. Stowell
Macalester Journal of Physics and Astronomy
Methane based gases are often used to produce thin films of biomaterials, such as diamond-like carbon, through Plasma Enhanced Chemical Vapor Deposition. The characterization of the H2 plasma will give a deeper understanding of the physical processes occurring. Understanding these processes could lead to the optimization of the production of these thin films in the future. In this paper, we examine the H2 plasma using a Langmuir probe to gain information on the electron temperature and density of the plasma discharge. We measured electron temperatures of 6eV. Our Langmuir probe data indicates the electron temperature remains constant as …
Dissociative Excitation Of H2 In An Rf Plasma,
2016
Macalester College
Dissociative Excitation Of H2 In An Rf Plasma, John Carlson
Macalester Journal of Physics and Astronomy
Plasma-enhanced chemical vapor deposition is a widely used method for depositing thin films. In order to optimize the properties of the films, it is important to understand the plasma processes that occur during film growth. In this research we use optical emission spectroscopy in order to measure the spectral emission lines of a plasma produced with hydrogen gas. In conjunction with other measurements and modeling, these measurements can provide insight to the electron energy distribution of the plasma.
Spontaneous Parametric Down Conversion Of Photons Through Β-Barium Borate,
2016
California Polytechnic State University, San Luis Obispo
Spontaneous Parametric Down Conversion Of Photons Through Β-Barium Borate, Luke Horowitz
Physics
An apparatus for detecting pairs of entangled 405nm photons that have undergone Spontaneous Parametric Down Conversion through β-Barium Borate is described. By using avalanche photo-diodes to detect the low-intensity converted beam and a coincidence module to register coincident photons, it is possible to create an apparatus than can be used to perform quantum information experiments under a budget appropriate for an undergraduate physics lab.
Modeling The Sps Feedback And Feedforward Systems For Improved Performance,
2016
California Polytechnic State University, San Luis Obispo
Modeling The Sps Feedback And Feedforward Systems For Improved Performance, Jake Hargrove
Physics
The Super Proton Synchrotron (SPS) is the last link in the chain of accelerators providing protons to the Large Hadron Collider (LHC). The SPS is currently the limiting factor on the maximum number of protons and thus collisions in the LHC. The SPS upgrade is under way to expand the discovery potential of the LHC. The accelerating system — Radio Frequency (RF) — is being improved. Models of the SPS RF feedback systems were developed. These models could assist with design choices, evaluating the upgraded system performance, and anticipate limitations and issues.
Diffractive Imaging Of A Rotational Wavepacket
In Nitrogen Molecules With Femtosecond Megaelectronvolt Electron Pulses,
2016
University of Nebraska-Lincoln
Diffractive Imaging Of A Rotational Wavepacket In Nitrogen Molecules With Femtosecond Megaelectronvolt Electron Pulses, Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Ryan Coffee, Jeff Corbett, Alan Fry, Kelly Gaffney, Tais Gorkhover, Carsten Hast, Keith Jobe, Igor Makasyuk, Alexander Reid, Joseph Robinson, Sharon Vetter, Fenglin Wang, Stephen Weathersby, Charles Yoneda, Martin Centurion, Xijie Wang
Martin Centurion Publications
This work is licensed under a Creative Commons Attribution 4.0 International License.
Manipulation Of Beams Of Ultra-Relativistic Electrons To Create Femtosecond X-Ray Pulses,
2016
University of Nebraska-Lincoln
Manipulation Of Beams Of Ultra-Relativistic Electrons To Create Femtosecond X-Ray Pulses, Jordan T. O'Neal, Austin Schulte, Rafal Rakowski, Matthias Fuchs
UCARE: Research Products
The research proposed here is expected to result in a crucial component used in a next-generation X-ray source. Typical conventional high-brightness X-ray sources (so-called synchrotron lightsources) are up to 30 football fields in size. Our group uses a novel technique based on ultrahigh-power lasers to develop a similar source that can readily fit into a single, university-scale laboratory. More specifically, the research conducted within this proposal will be concerned with the manipulation of beams of ultra-relativistic electrons, (electrons that move with almost the speed of light) with the goal to focus the particles into an area that is smaller than …
Plasma Processing Of Superconducting Radio Frequency Cavities,
2016
Old Dominion University
Plasma Processing Of Superconducting Radio Frequency Cavities, Janardan Upadhyay
Physics Theses & Dissertations
The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb …
Population Density Measurements Of The Excited States Of An Optically Excited Argon Discharge Using Emission And Absorption Spectroscopy,
2016
Air Force Institute of Technology
Population Density Measurements Of The Excited States Of An Optically Excited Argon Discharge Using Emission And Absorption Spectroscopy, Steven A. Owens
Theses and Dissertations
The populations of the excited argon 3s23p54s (s5 only) and 3s23p54p configurations in a 10 W radio frequency discharge has been studied using optical emission and diode laser absorption spectroscopy. By optically bleaching the s5→p9 transition with a narrow band laser pump of about 10 W/cm2 at 811 nm, the p9 population was increased by about a factor of 2 at a pressure of 5 Torr. At higher pressure, collisional mixing to adjacent p-states limited the laser-increased p9 population to less than 10 percent. All other laser-induced p-state populations were minimally …
Kinetics Of Higher Lying Rb States After, Pulsed Excitation Of The D2 Transition In The Presence Of Helium,
2016
Air Force Institute of Technology
Kinetics Of Higher Lying Rb States After, Pulsed Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein
Theses and Dissertations
The Diode Pumped Alkali Laser (DPAL) is a high power, three-level laser system that employs diode bars to optically excite an alkali metal vapor. It lases along the D1 transition, between the two lowest energy levels, 2P1/2 and 2S1/2. Higher lying energy states are produced at higher population density via energy pooling and multiphoton processes. Pulsed laser excitation of rubidium at approximately 1 MW=cm2 has been studied at helium pressure up to 900 Torr. Emissions from energy states as high as 82D suggests modest ionization, though these intensities decrease drastically at buffer gas …
Localized Plasma Measurement During Instability Modes In A Hall Thruster,
2016
Air Force Institute of Technology
Localized Plasma Measurement During Instability Modes In A Hall Thruster, David A. Cunningham
Theses and Dissertations
Hall thrusters are a key technology for current and future unmanned satellites, striking a balance between thrust and fuel economy suitable for many mission profiles of interest. Despite their extensive flight heritage and a large body of research, many phenomena occurring in the plasma discharge of Hall thrusters are not well understood. A combination of intrusive and non-intrusive measurement techniques were used to investigate the properties of the exhaust plume of two Hall thrusters and correlate optical characteristics of oscillating modes with the plasma potential and azimuthal current distribution during those modes. A strong trend was found associating the optical …
Atomic Photoionization Experiment By Harmonic-Generation Spectroscopy,
2016
Voronezh State University, Russia
Atomic Photoionization Experiment By Harmonic-Generation Spectroscopy, M. V. Frolov, T. S. Sarantseva, N. L. Manakov, K. D. Fulfer, B. P. Wilson, J. Troß, X. Ren, Erwin D. Poliakoff, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace, C. A. Trallero-Herrero
Anthony F. Starace Publications
Measurements of the high-order-harmonic generation yield of the argon (Ar) atom driven by a strong elliptically polarized laser field are shown to completely determine the field-free differential photoionization cross section of Ar, i.e., the energy dependence of both the angle-integrated photoionization cross section and the angular distribution asymmetry parameter.
The Subject Librarian Newsletter, Creol, Spring 2016,
2016
University of Central Florida
The Subject Librarian Newsletter, Creol, Spring 2016, Patti Mccall
Libraries' Newsletters
No abstract provided.
Control Of Threshold Enhancements In Harmonic Generation By Atoms In A Two-Color Laser Field With Orthogonal Polarizations,
2016
Voronezh State University, Russia
Control Of Threshold Enhancements In Harmonic Generation By Atoms In A Two-Color Laser Field With Orthogonal Polarizations, M. V. Frolov, N. L. Manakov, T. S. Sarantseva, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace
Anthony F. Starace Publications
Threshold phenomena (or channel-closing effects) are analyzed in high-order harmonic generation (HHG) by atoms in a two-color laser field with orthogonal linearly polarized components of a fundamental field and its second harmonic. We show that the threshold behavior of HHG rates for the case of a weak second harmonic component is sensitive to the parity of a closing multiphoton ionization channel and the spatial symmetry of the initial bound state of the target atom, while for the case of comparable intensities of both components, suppression of threshold phenomena is observed as the relative phase between the components of a two-color …
Ultrafast Imaging Of Isolated Molecules With Electron Diffraction,
2016
University of Nebraska-Lincoln
Ultrafast Imaging Of Isolated Molecules With Electron Diffraction, Martin Centurion
Martin Centurion Publications
Recent advances in ultrafast electron diffraction offer the possibility to image isolated molecules with sub-Angstrom spatial resolution in ultrafast time scales. In particular, diffraction from aligned molecules has opened the door to retrieving three-dimensional structures directly from experimental data. In this manuscript we review the progress in ultrafast gas electron diffraction and discuss remaining challenges to achieve a temporal resolution of sub-100 fs, which is needed to observe the nuclear motion in chemical reactions in the gas phase.
Eikonal Perturbation Theory In Photoionization,
2016
University of Warsaw
Eikonal Perturbation Theory In Photoionization, F. Cajiao Vélez, Katarzyna Krajewska, J. Z. Kamiński
Department of Physics and Astronomy: Faculty Publications
The eikonal perturbation theory is formulated and applied to photoionization by strong laser pulses. A special emphasis is put on the first order approximation with respect to the binding potential, which is known as the generalized eikonal approximation [2015 Phys. Rev. A 91 053417]. The ordinary eikonal approximation and its domain of applicability is derived from the generalized eikonal approximation. While the former approach is singular for the electron trajectories which return to the potential center, the generalized eikonal avoids this problem. This property makes it a promising tool for further investigations of rescattering and high-order harmonic generation processes.
Control And Optimization Of A Staged Laser-Wakefield Accelerator,
2016
University of Nebraska-Lincoln
Control And Optimization Of A Staged Laser-Wakefield Accelerator, Grigory V. Golovin, Sudeep Banerjee, Shouyuan Chen, Nathan D. Powers, Cheng Liu, Wenchao Yan, Jia Zhang, Ping Zhang, Baozhen Zhao, Donald Umstadter
Donald Umstadter Publications
We report results of an experimental study of laser-wakefield acceleration of electrons, using a staged device based on a double-jet gas target that enables independent injection and acceleration stages. This novel scheme is shown to produce stable, quasi-monoenergetic, and tunable electron beams. We show that optimal accelerator performance is achieved by systematic variation of five critical parameters. For the injection stage, we show that the amount of trapped charge is controlled by the gas density, composition, and laser power. For the acceleration stage, the gas density and the length of the jet are found to determine the final electron energy. …
Improving The Efficiency And Resolution Of Time Of Flight (Tof) Mass Spectrometer For Magnetospheric Applications.,
2016
University of New Hampshire, Durham
Improving The Efficiency And Resolution Of Time Of Flight (Tof) Mass Spectrometer For Magnetospheric Applications., Zain Abbas
Honors Theses and Capstones
The Earth magnetosphere is the volume of space formed by the Earth magnetic field in response to the flow of plasma from the solar wind. Although the magnetopause shields us from the solar wind there are far more particles that penetrate with energy, and momentum to the Earths magnetosphere and interacts with the Earth’s magnetic field to create various plasmas and currents which shape and couple different regions of magnetosphere. The study of the dynamics of ions in and outside of the magnetosphere is done through mass spectrometer. Over the years, CODIF Ion TOF spectrometer have been used to understand …
Coherent Beam Combining Of Ultrashort Laser Pulses,
2016
University of Central Florida
Coherent Beam Combining Of Ultrashort Laser Pulses, Ahmad Azim
Honors Undergraduate Theses
Ultrashort pulsed lasers have become critical to understanding light-matter interactions in new regimes such as generation of attosecond pulses, laser filamentation, and intense relativistic processes. Development of more powerful and energetic ultrafast lasers is required for advancing these fields of study. Several petawatt class systems now exist with more in development to further scale peak power and extend the frontier of ultrafast laser technology. Another relevant solution to the scaling of energy and power of ultrashort pulses is coherent beam combining (CBC). CBC is useful for not only scaling of laser parameters but also to mitigate parasitic nonlinear processes associated …
20 Years Of Microplasma Research: A Status Report,
2016
Old Dominion University
20 Years Of Microplasma Research: A Status Report, Karl H. Schoenbach, Kurt Becker
Bioelectrics Publications
The field of microplasmas gained recognition as a well-defined area of research and application within the larger field of plasma science and technology about 20 years ago. Since then, the activity in microplasma research and applications has continuously increased. A survey of peer reviewed papers on microplasmas published annually shows a steady increase from fewer than 20 papers in 1995 to about 75 in 2005 and more than 150 in 2014. This count excludes papers that deal exclusively with technological applications where the microplasma is used solely as a tool. This topical review aims to provide a snap shot of …
