Comparison Between Electropositive And Electronegative Cold Atmospheric-Pressure Plasmas: A Modelling Study,
2016
Old Dominion University
Comparison Between Electropositive And Electronegative Cold Atmospheric-Pressure Plasmas: A Modelling Study, Ding X. Liu, Jia F. Li, Ai J. Yang, Xiao H. Wang, Ming Z. Rong, Michael G. Kong
Bioelectrics Publications
Cold atmospheric-pressure He + N2 and He + O2 plasmas are chosen as the representatives for electropositive and electronegative plasmas, of which the discharge characteristics are studied and then compared to each other by fluid models. As the increase of the impurity (N2 or O2) fraction from 0 to 10%, for He + N2 plasmas the electron density and ion density increase, the spatiotemporal distributions of electron density, ion density, electron temperature and electron generation rate change a little. On contrast, for He + O2 plasmas the electron density decreases, the ion density …
Plasma Temperature Measurements In The Context Of Spectral Interference,
2016
University of Central Florida
Plasma Temperature Measurements In The Context Of Spectral Interference, Brandon Seesahai
Honors Undergraduate Theses
The path explored in this thesis is testing a plasma temperature measurement approach that accounts for interference in a spectrum. The Atomic Emission Spectroscopy (AES) technique used is called Laser Induced Breakdown Spectroscopy (LIBS) and involves focusing a laser pulse to a high irradiance onto a sample to induced a plasma. Spectrally analyzing the plasma light provides a "finger print" or spectrum of the sample. Unfortunately, spectral line broadening is a type of interference encountered in a LIBS spectrum because it blends possible ionic or atomic transitions that occur in plasma. To make use of the information or transitions not …
Shielded Radiography With A Laser-Driven Mev-Energy X-Ray Source,
2016
University of Nebraska–Lincoln
Shielded Radiography With A Laser-Driven Mev-Energy X-Ray Source, Shouyuan Chen, Grigory V. Golovin, Cameron Miller, Daniel Haden, Sudeep Banerjee, Ping Zhang, Cheng Liu, Jun Zhang, Baozhen Zhao, Shaun Clarke, Sara Pozzi, Donald Umstadter
Donald Umstadter Publications
We report the results of experimental and numerical-simulation studies of shielded radiography using narrowband MeVenergy X-rays from a compact all-laser-driven inverse-Compton-scattering X-ray light source. This recently developed Xray light source is based on a laser-wakefield accelerator with ultra-high-field gradient (GeV/cm). We demonstrate experimentally high-quality radiographic imaging (image contrast of 0.4 and signal-to-noise ratio of 2:1) of a target composed of 8-mm thick depleted uranium shielded by 80-mm thick steel, using a 6-MeV X-ray beam with a spread of 45% (FWHM) and 107 photons in a single shot. The corresponding dose of the X-ray pulse measured in front of the target …
Plasma Density Analysis Of Cubesat Wakes In The Earth’S Ionosphere,
2016
Embry-Riddle Aeronautical University
Plasma Density Analysis Of Cubesat Wakes In The Earth’S Ionosphere, Robert M. Albarran Ii, Aroh Barjatya
Publications
Spinning or tumbling CubeSats with Langmuir probes deployed on booms will render spin-modulated plasma densities as the probes move in and out of the spacecraft wake. It is traditionally assumed that the lower-density measurements from the spin cycle are made in the spacecraft wake, and the higher-density measurements are outside the wake. Although this assumption is valid for larger spacecraft in the Earth’s ionosphere, this paper scrutinizes its validity for CubeSats in similar conditions. Spacecraft–plasma interactions (surface charging, plasma sheaths, and wakes) are less understood for CubeSats, and the small CubeSat dimensions must be considered with respect to characteristic length …
Simulation Of Nuclear Fusion Using A One Dimensional Particle In Cell Method,
2016
Humboldt State University
Simulation Of Nuclear Fusion Using A One Dimensional Particle In Cell Method, Steven T. Margell
Cal Poly Humboldt theses and projects
In this thesis several novel techniques are developed to simulate fusion events in an isotropic, electrostatic three-dimensional Deuterium-Tritium plasma. These techniques allow us to accurately predict three-dimensional collision events with a one-dimensional model while simultaneously reducing compute time via a nearest neighbor algorithm. Furthermore, a fusion model based on first principles is developed that yields an average fusion reactivity which correlates well with empirical results.
Theoretical Estimates Of Spherical And Chromatic Aberration In Photoemission Electron Microscopy,
2016
Portland State University
Theoretical Estimates Of Spherical And Chromatic Aberration In Photoemission Electron Microscopy, Joseph P. S. Fitzgerald, Robert Campbell Word, Rolf Kӧnenkamp
Physics Faculty Publications and Presentations
We present theoretical estimates of the mean coefficients of spherical and chromatic aberration for low energy photoemission electron microscopy (PEEM). Using simple analytic models, we find that the aberration coefficients depend primarily on the difference between the photon energy and the photoemission threshold, as expected. However, the shape of the photoelectron spectral distribution impacts the coefficients by up to 30%. These estimates should allow more precise correction of aberration in PEEM in experimental situations where the aberration coefficients and precise electron energy distribution cannot be readily measured.
Multicharged Carbon Ion Generation From Laser Plasma,
2016
Old Dominion University
Multicharged Carbon Ion Generation From Laser Plasma, Oguzhan Balki, Hani E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Carbon ions generated by ablation of a carbon target using an Nd:YAG laser pulse (wavelength λ = 1064 nm, pulse width τ = 7 ns, and laser fluence of 10-110 J cm-2) are characterized. Time-of-flight analyzer, a three-mesh retarding field analyzer, and an electrostatic ion energy analyzer are used to study the charge and energy of carbon ions generated by laser ablation. The dependencies of the ion signal on the laser fluence, laser focal point position relative to target surface, and the acceleration voltage are described. Up to C4+ ions are observed. When no acceleration voltage is applied between the …
A Feasibility Study Of A Nuclear Power Plant With No Moving Parts,
2016
Missouri University of Science and Technology
A Feasibility Study Of A Nuclear Power Plant With No Moving Parts, Jonathan Mark Schattke
Masters Theses
"In a nuclear reactor design, every moving part in a system is considered a failure point. In this study, a proposal is made for designing a nuclear reactor that has no moving parts by coupling an accelerator driven core (removing control system moving parts) to a magnetohydrodynamic generator (removing power generation moving parts) using mercury coolant (removing pumping system moving parts). Further safety is realized by using a subcritical core, where the core is never able to sustain a chain reaction on its own, obviating many safety systems. The design is verified with a Monte Carlo simulation "--Abstract, page iii.
Intensity Control Of Dielectric Barrier Discharge Filaments,
2016
Missouri University of Science and Technology
Intensity Control Of Dielectric Barrier Discharge Filaments, Matthew Crawford Paliwoda
Masters Theses
"When operated in a filamentary mode, a volume dielectric barrier discharge (DBD) is known to produce patterned plasma structures. These structures are currently being explored for reconfigurable metamaterial applications. In this work the presence and intensity of a single filament, within an array of filaments, was controlled by adjusting the voltage to that filament's individual needle electrode. The current, voltage, and time-averaged normalized light intensity were measured while varying the voltage of the needle through a self-biasing resistance. For a 7.5 kV, 3.2 kHz DBD in air, the needle-controlled filament intensity varies from that of the surrounding filaments to zero …
Analyses Of 476 Mhz And 952 Mhz Crab Cavities For Jlab Electron Ion Collider,
2016
Old Dominion University
Analyses Of 476 Mhz And 952 Mhz Crab Cavities For Jlab Electron Ion Collider, Hyekyoung Park, A. Castilla, J. R. Delayen, S. U. De Silva, V. Morozov
Physics Faculty Publications
Center for Accelerator Science at ODU has designed, fabricated and successfully tested a crab cavity for MEIC at Jefferson Lab*. This proof of principle cavity was based on the earlier MEIC design which used 748.5 MHz RF system. The updated MEIC design** utilizes the components from PEP-II. It results in the change on the bunch repetition rate of stored beam to 476.3 MHz. The ion ring collider will eventually require 952.6 MHz crab cavity. This paper will present the analyses of crab cavities of both 476 MHz and 952 MHz options. It compares advantages and disadvantages of the options which …
Harmonically Resonant Cavity As A Bunch-Length Monitor,
2016
Old Dominion University
Harmonically Resonant Cavity As A Bunch-Length Monitor, B. Roberts, F. Hannon, M. M. Ali, E. Forman, J. Grames, R. Kazimi
Physics Faculty Publications
A compact, harmonically resonant cavity with fundamental resonant frequency 1497 MHz was used to evaluate the temporal characteristics of electron bunches produced by a 130 kV dc high voltage spin-polarized photoelectron source at the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector, delivered at 249.5 and 499 MHz repetition rates and ranging in width from 45 to 150 picoseconds (FWHM). A cavity antenna attached directly to a sampling oscilloscope detected the electron bunches as they passed through the cavity bore with a sensitivity of ∼1 mV/μA . The oscilloscope waveforms are a superposition of the harmonic modes excited by the beam, …
Combining Diffusive Shock Acceleration And Stochastic Particle Energization By Multiple Plasmoids,
2015
University of Alabama in Huntsville
Combining Diffusive Shock Acceleration And Stochastic Particle Energization By Multiple Plasmoids, Parisa Mostafavi
Von Braun Symposium Student Posters
No abstract provided.
Electron Vortices In Photoionization By Circularly Polarized Attosecond Pulses,
2015
University of Nebraska-Lincoln
Electron Vortices In Photoionization By Circularly Polarized Attosecond Pulses, Jean Marcel Ngoko Djiokap, S. X. Hu, L. B. Madsen, N. L. Manakov, A. V. Meremianin, Anthony F. Starace
Anthony F. Starace Publications
Single ionization of He by two oppositely circularly polarized, time-delayed attosecond pulses is shown to produce photoelectron momentum distributions in the polarization plane having helical vortex structures sensitive to the time delay between the pulses, their relative phase, and their handedness. Results are obtained by both ab initio numerical solution of the two-electron time-dependent Schrödinger equation and by a lowest-order perturbation theory analysis. The energy, bandwidth, and temporal duration of attosecond pulses are ideal for observing these vortex patterns.
Simulations Of Hl-Lhc Crab Cavity Noise Using Headtail,
2015
California Polytechnic State University - San Luis Obispo
Simulations Of Hl-Lhc Crab Cavity Noise Using Headtail, Stanley Steeper
Physics
The High Luminosity Large Hadron Collider (Hi-Lumi LHC) upgrade -- scheduled to be completed by 2025 -- will improve the existing LHC in many ways. One such upgrade is the addition of Crab Cavities (CCs). The CCs are resonant structures that provide strong transverse kicks to the circulating clouds of particles around each interaction region. As such, the CCs result in a head-on collision of the clouds and a large increase in event rate, leading to reduced statistical uncertainty and potentially faster discoveries. However, the CC field will be modulated by phase and amplitude noise which can have detrimental effects …
Kinetic Modeling Of Roll To Roll Rfcvd Plasma,
2015
Purdue University
Kinetic Modeling Of Roll To Roll Rfcvd Plasma, Kudzo S. Ahegbebu, Siva Sashank Tholeti, Alina A. Alexeenko
The Summer Undergraduate Research Fellowship (SURF) Symposium
Roll-to-roll radio frequency plasma enhanced chemical vapor deposition (R2R RFCVD) is a technique for large-scale synthesis of high quality graphitic nanopetals. Graphitic nanopetals are petal-like graphene structures with remarkable electrical and mechanical properties with major industrial applications such as microsupercapacitors. RFCVD uses a non-equilibrium plasma with high energy electrons to catalyze chemical reactions, induce the creation of free radicals, and promote otherwise high temperature chemistry in a low temperature environment. Understanding how bulk plasma characteristics (particularly, power and number densities) vary with changing reactor parameters is an important step towards optimizing synthesis techniques. In our present work we use the …
Optical Emission Spectroscopy Diagnostics Of Cold Plasmas For Food Sterilization,
2015
Purdue University
Optical Emission Spectroscopy Diagnostics Of Cold Plasmas For Food Sterilization, Abhijit Jassem, Michael Lauria, Russell Brayfield Ii, Kevin M. Keener, Allen L. Garner
The Summer Undergraduate Research Fellowship (SURF) Symposium
There is a growing need for economical, effective, and safe methods of sterilizing fresh produce. The most common method is a chlorine wash, which is expensive and may introduce carcinogens. High voltage cold atmospheric pressure plasmas are a promising solution that has demonstrated a germicidal effect; however, the responsible chemical mechanisms and reaction pathways are not fully understood. To elucidate this chemistry, we used optical emission spectroscopy to measure the species produced in the plasma generated by a 60 Hz pulsed dielectric barrier discharge in a plastic box containing various fill gases (He, N2, CO2, dry …
Favorable Target Positions For Intense Laser Acceleration Of Electrons In Hydrogen-Like, Highly-Charged Ions,
2015
University of Nebraska-Lincoln
Favorable Target Positions For Intense Laser Acceleration Of Electrons In Hydrogen-Like, Highly-Charged Ions, Liang-Wen Pi, S. X. Hu, Anthony F. Starace
Anthony F. Starace Publications
Classical relativistic Monte Carlo simulations of petawatt laser acceleration of electrons bound initially in hydrogen-like, highly-charged ions show that both the angles and energies of the laser-accelerated electrons depend on the initial ion positions with respect to the laser focus. Electrons bound in ions located after the laser focus generally acquire higher (≈GeV) energies and are ejected at smaller angles with respect to the laser beam. Our simulations assume a tightly-focused linearly-polarized laser pulse with intensity approaching 1022W/cm2. Up to fifth order corrections to the paraxial approximation of the laser field in the focal region are …
Scaling Laws For High-Order-Harmonic Generation With Midinfrared Laser Pulses,
2015
Voronezh State University, Russia
Scaling Laws For High-Order-Harmonic Generation With Midinfrared Laser Pulses, M. V. Frolov, N. L. Manakov, Wei-Hao Xiong, Liang-You Peng, J. Burgdörfer, Anthony F. Starace
Anthony F. Starace Publications
We derive an analytic expression for thewavelength scaling of the high-order-harmonic generation (HHG) yield induced by midinfrared driving laser fields. It is based on a quasiclassical description of the returning electron wave packet, which is shown to be largely independent of atomic properties. The accuracy of this analytic expression is confirmed by comparison with results of numerical solutions of the time-dependent Schr¨odinger equation for wavelengths in the range of 1.4 μm ≤ λ ≤ 4 μm. We verify the wavelength scaling of the HHG yield found numerically for midinfrared laser fields in a recent paper by Le et al. [
Photodetachment Of A Model Molecular System By An Elliptically Polarized Field,
2015
Voronezh State University, Russia
Photodetachment Of A Model Molecular System By An Elliptically Polarized Field, M. V. Frolov, N. L. Manakov, S. S. Marmo, Anthony F. Starace
Anthony F. Starace Publications
The differential cross section for one-photon molecular detachment by an elliptically polarized field is analyzed for a one-electron molecular model comprised of an electron in the field of two (generally nonequivalent) attractive zero-range potentials (ZRPs) separated by the distance R. A phenomenological parametrization of the photodetachment cross section for a fixed-in-space molecular system in terms of two scalar dynamical parameters is presented and circular dichroism effects are discussed. Analytic results for the dynamical molecular parameters within the ZRP molecular model are used to analyze interference phenomena (including two-center interference) and dichroic effects in the detached electron angular distributions and …
Auto-Concealment Of Supersymmetry In Extra Dimensions,
2015
Stanford University
Auto-Concealment Of Supersymmetry In Extra Dimensions, Savas Dimopoulos, Kiel Howe, John March-Russell, James A. Scoville
Faculty Publications
In supersymmetric (SUSY) theories with extra dimensions the visible energy in sparticle decays can be significantly reduced and its energy distribution broadened, thus significantly weakening the present collider limits on SUSY. The mechanism applies when the lightest supersymmetric particle (LSP) is a bulk state — e.g. a bulk modulino, axino, or gravitino — the size of the extra dimensions ≳ 10−14 cm, and for a broad variety of visible sparticle spectra. In such cases the lightest ordinary supersymmetric particle (LOSP), necessarily a brane-localised state, decays to the Kaluza-Klein (KK) discretuum of the LSP. This dynamically realises the compression mechanism …
