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Full-Text Articles in Physics

Evaluation Of X-Ray Spectroscopic Techniques For Determining Temperature And Density In Plasmas, Theodore Scott Lane Jan 2019

Evaluation Of X-Ray Spectroscopic Techniques For Determining Temperature And Density In Plasmas, Theodore Scott Lane

Graduate Theses, Dissertations, and Problem Reports

Temperature and density measurements of plasmas are important for understanding various phenomena. For example, equations of state, most scaling arguments for Inertial Confinement Fusion and laboratory astrophysics all rely upon accurate knowledge of temperature and density. Spectroscopy is a non-invasive technique to measure these quantities. In this work we establish a new spectroscopic technique by using it to determine temperature. We also compare and contrast the capability of two codes, PrismSPECT and ATOMIC, to infer electron density from experimentally acquired spectra via Stark broadening.

We compare and contrast the capability of isoelectronic line ratios and inter-stage line ratios in an ...


Hybrid Iterative Approach For Simulation Of Radio-Frequency Fields In Plasma, Vladimir A. Svidzinski, Jin-Soo Kim, Liangji Zhao, S. A. Galkin, Joseph Andrew Spencer Aug 2018

Hybrid Iterative Approach For Simulation Of Radio-Frequency Fields In Plasma, Vladimir A. Svidzinski, Jin-Soo Kim, Liangji Zhao, S. A. Galkin, Joseph Andrew Spencer

Physics Student Research

A novel iterative approach for solving discretized linear wave equations in a frequency domain, which combines time evolution with iterative relaxation schemes, is presented. In this hybrid approach, each iteration cycle consists of evolution of electromagnetic (EM) fields in time over a specified number of field periods followed by several iterative relaxations. Provided that there is sufficient dissipation, both the time evolution and the iterative relaxations contribute to the convergence of the EM fields to the solution of the formulated full wave boundary value problem. Time evolution rapidly distributes EM fields, propagating with group velocity, over the simulation domain, while ...


Statistical Physics Principles Tested Using Dusty Plasma And Aerosol Experiments, Chun-Shang Wong Aug 2018

Statistical Physics Principles Tested Using Dusty Plasma And Aerosol Experiments, Chun-Shang Wong

Theses and Dissertations

Statistical physics has been the foundation for much of our understanding about plasma physics. Often, plasma physics phenomena are explained using statistical physics principles and theories. Here, I reverse this paradigm to instead use plasma experiments to test statistical physics principles.

In this thesis, I test statistical physics principles with an experimental dusty plasma, which is a four-component mixture of micron-sized ``dust'' particles, electrons, ions, and neutral gas molecules. When immersed in the plasma, the dust particles acquire large negative charges, since they accumulate more electrons than ions. Due to their large electric charges, the dust particles have interparticle potential ...


Kinetic Picture Of Ion Acoustic Wave Reflection Using Laser-Induced Fluorescence, Jorge Alberto Berumen Cantu Aug 2018

Kinetic Picture Of Ion Acoustic Wave Reflection Using Laser-Induced Fluorescence, Jorge Alberto Berumen Cantu

Theses and Dissertations

An examination of the first laser-induced fluorescence measurements of ion-acoustic wave reflection is presented in this dissertation. The experiment is performed in a multipole cylinindrical chamber using singly-ionized argon (ArII) plasma produced by a means of a hot cathode. Ion-acoustic waves are launched from a mesh antenna and reflected/absorbed by a biased, solid boundary (electrode). A kinetic analysis of wave reflection is carried out through LIF's ability of resolving ion phase-space. A comparison between Langmuir probe and LIF diagnostics is presented, with complementary Electric-field probe measurements.


Actinometry Of Hydrogen Plasmas, A. M. Cotter, James Doyle Jun 2018

Actinometry Of Hydrogen Plasmas, A. M. Cotter, James Doyle

Macalester Journal of Physics and Astronomy

Optical emission spectroscopy (OES) can be used to map the electron energy distribution of hydrogen plasmas. Using actinometry, a type of OES where trace amounts of noble gases are introduced, the effect of discharge power on the electron temperature of hydrogen plasmas was explored. This was done using argon and krypton as actinometers for low pressure hydrogen plasmas. It was determined that the electron temperature decreased with respect to power supplied to the discharge.


Hill Functions For Stochastic Gene Regulatory Networks From Master Equations With Split Nodes And Time-Scale Separation, Ovidiu Lipan, Cameron Ferwerda Feb 2018

Hill Functions For Stochastic Gene Regulatory Networks From Master Equations With Split Nodes And Time-Scale Separation, Ovidiu Lipan, Cameron Ferwerda

Physics Faculty Publications

The deterministic Hill function depends only on the average values of molecule numbers. To account for the fluctuations in the molecule numbers, the argument of the Hill function needs to contain the means, the standard deviations, and the correlations. Here we present a method that allows for stochastic Hill functions to be constructed from the dynamical evolution of stochastic biocircuits with specific topologies. These stochastic Hill functions are presented in a closed analytical form so that they can be easily incorporated in models for large genetic regulatory networks. Using a repressive biocircuit as an example, we show by Monte Carlo ...


A Parallel Spectral Method Approach To Model Plasma Instabilities, Kevin S. Scheiman Jan 2018

A Parallel Spectral Method Approach To Model Plasma Instabilities, Kevin S. Scheiman

Browse all Theses and Dissertations

The study of solar-terrestrial plasma is concerned with processes in magnetospheric, ionospheric, and cosmic-ray physics involving different particle species and even particles of different energy within a single species. Instabilities in space plasmas and the earth's atmosphere are driven by a multitude of free energy sources such as velocity shear, gravity, temperature anisotropy, electron, and, ion beams and currents. Microinstabilities such as Rayleigh-Taylor and Kelvin-Helmholtz instabilities are important for the understanding of plasma dynamics in presence of magnetic field and velocity shear. Modeling these turbulences is a computationally demanding processes; requiring large memory and suffer from excessively long runtimes ...


Properties Of Nonlinear Solitary Structures In Astrophysical And Space Plasmas, Justin C. Holmes Jan 2018

Properties Of Nonlinear Solitary Structures In Astrophysical And Space Plasmas, Justin C. Holmes

Astrophysical & Planetary Sciences Graduate Theses & Dissertations

Solitary waves are a commonly observed form of strong electric fields parallel to the back- ground magnetic field in space plasmas. It has been repeatedly suggested that they have a significant influence on the surrounding environment, either individually or as a collective. At a minimum, nonlinear waves appear to be signposts for important plasma processes such as magnetic reconnec- tion and turbulence. Understanding the effects of solitary waves on the macro-scale first requires us to characterize their structure on the micro-scale. In this thesis, I examine solitary waves of several flavors using a combination of simulations and high time resolution ...


An Analysis Of Scientific Data Quality For The Fast Plasma Investigation Of The Mms Mission, Alexander C. Barrie Jan 2018

An Analysis Of Scientific Data Quality For The Fast Plasma Investigation Of The Mms Mission, Alexander C. Barrie

Aerospace Engineering Sciences Graduate Theses & Dissertations

This work describes technical innovations to improve the data quality and volume for the Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale mission (MMS). A parametric study of wavelet compression has shown that plasma count data can be compressed to high compression ratios with a minimal effect on the integrated plasma moments. Different regions of the magnetosphere are analyzed for both electron and ion count data. The FPI trigger data, intended as a data ranking metric, has been adapted and corrected to a point where scientifically accurate pseudo moments can be generated and released to the research community, drastically ...


A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, Tiejun Xiao, Xueyu Song Dec 2017

A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, Tiejun Xiao, Xueyu Song

Ames Laboratory Accepted Manuscripts

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in ...


Nonlinear Waves, Instabilities And Singularities In Plasma And Hydrodynamics, Denis Albertovich Silantyev Aug 2017

Nonlinear Waves, Instabilities And Singularities In Plasma And Hydrodynamics, Denis Albertovich Silantyev

Mathematics & Statistics ETDs

This work concentrates on Langmuir wave filamentation instability in the kinetic regime of plasma and computation of Stokes wave with high precision using conformal maps.

Nonlinear effects are present in almost every area of science as soon as one tries to go beyond the first order approximation. In particular, nonlinear waves emerge in such areas as hydrodynamics, nonlinear optics, plasma physics, quantum physics, etc. The results of this work are related to nonlinear waves in two areas, plasma physics and hydrodynamics, united by concepts of instability, singularity and advanced numerical methods used for their investigation.

The first part of this ...


On Laser-Induced Plasma Containing Hydrogen, Ghaneshwar Gautam Aug 2017

On Laser-Induced Plasma Containing Hydrogen, Ghaneshwar Gautam

Doctoral Dissertations

Laser-induced micro-plasma dynamics are investigated in laboratory air, ultra-high-pure hydrogen gas, and hydrogen-nitrogen gas mixtures. The dissertation focuses on atomic spectroscopy of hydrogen in the visible region.

Line-of-sight measurements are analyzed to obtain spatial distributions of electron densities and excitation temperatures. The studies include evaluation of self-absorption phenomena. The plasma dynamics occur initially well above re-entry speeds and diminish to hypersonic and then supersonic expansions. Expansion velocities are measured that are above three hundred times the speed of sound in standard atmosphere. Optical breakdown is induced by using pulsed laser radiation. Emission spectra are collected by employing a spectrometer equipped ...


Accelerator Based Fusion Reactor, Keh-Fei Liu, Alexander Wu Chao Aug 2017

Accelerator Based Fusion Reactor, Keh-Fei Liu, Alexander Wu Chao

Physics and Astronomy Faculty Publications

A feasibility study of fusion reactors based on accelerators is carried out. We consider a novel scheme where a beam from the accelerator hits the target plasma on the resonance of the fusion reaction and establish characteristic criteria for a workable reactor. We consider the reactions d+tn+α, d+3Hep+α and p+11B→3α in this study. The critical temperature of the plasma is determined from overcoming the stopping power of the beam with the fusion energy gain. The needed plasma lifetime is determined from the width of the resonance, the beam ...


The Impact Of Base Stacking On The Conformations And Electrostatics Of Single-Stranded Dna, Alex Plumridge, Steve P. Meisburger, Kurt Andresen, Lois Pollack Feb 2017

The Impact Of Base Stacking On The Conformations And Electrostatics Of Single-Stranded Dna, Alex Plumridge, Steve P. Meisburger, Kurt Andresen, Lois Pollack

Physics and Astronomy Faculty Publications

Single-stranded DNA (ssDNA) is notable for its interactions with ssDNA binding proteins (SSBs) during fundamentally important biological processes including DNA repair and replication. Previous work has begun to characterize the conformational and electrostatic properties of ssDNA in association with SSBs. However, the conformational distributions of free ssDNA have been difficult to determine. To capture the vast array of ssDNA conformations in solution, we pair small angle X-ray scattering with novel ensemble fitting methods, obtaining key parameters such as the size, shape and stacking character of strands with different sequences. Complementary ion counting measurements using inductively coupled plasma atomic emission spectroscopy ...


Laser Shock Wave Assisted Patterning On Niti Shape Memory Alloy Surfaces, Dovletgeldi Seyitliyev, Peizhen Li, Khomidkhodza Kholikov, Byron Grant, Haluk E. Karaca, Ali O. Er Feb 2017

Laser Shock Wave Assisted Patterning On Niti Shape Memory Alloy Surfaces, Dovletgeldi Seyitliyev, Peizhen Li, Khomidkhodza Kholikov, Byron Grant, Haluk E. Karaca, Ali O. Er

Mechanical Engineering Faculty Publications

An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface ...


Preface To Special Topic: A Tribute To John Lumley, Kiran Bhaganagar, Thomas B. Gatski, William K. George Feb 2017

Preface To Special Topic: A Tribute To John Lumley, Kiran Bhaganagar, Thomas B. Gatski, William K. George

CCPO Publications

This Special Topic Section is dedicated to the life and memory of John Leask Lumley(1930-2015), professor and scientist extraordinaire.


Kinetic Electric Field Signatures Associated With Magnetic Turbulence And Their Impact On Space Plasma Environments, Katherine Amanda Goodrich Jan 2017

Kinetic Electric Field Signatures Associated With Magnetic Turbulence And Their Impact On Space Plasma Environments, Katherine Amanda Goodrich

Astrophysical & Planetary Sciences Graduate Theses & Dissertations

Magnetic turbulence is a universal phenomenon that occurs in space plasma physics, the small-scale processes of which is not well understood. This thesis presents on observational analysis of kinetic electric field signatures associated with magnetic turbulence, in an attempt to examine its underlying microphysics. Such kinetic signatures include small-scale magnetic holes, double layers, and phase-space holes. The first and second parts of this thesis present observations of small-scale magnetic holes, observed depressions in total magnetic field strength with spatial widths on the order of or less than the ion Larmor radius, in the near-Earth plasmasheet. Here I demonstrate electric field ...


Regionally Implicit Discontinuous Galerkin Methods For Solving The Relativistic Vlasov-Maxwell System, Pierson Guthrey Jan 2017

Regionally Implicit Discontinuous Galerkin Methods For Solving The Relativistic Vlasov-Maxwell System, Pierson Guthrey

Graduate Theses and Dissertations

The relativistic Vlasov-Maxwell system (RVM) models the behavior of collisionless plasma, where electrons and ions interact via the electromagnetic fields they generate. In the RVM system, electrons could accelerate to significant fractions of the speed of light. An idea that is actively being pursued by several research groups around the globe is to accelerate electrons to relativistic speeds by hitting a plasma with an intense laser beam. As the laser beam passes through the plasma it creates plasma wakes, much like a ship passing through water, which can trap electrons and push them to relativistic speeds. Such setups are known ...


Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson Jan 2017

Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson

Graduate College Dissertations and Theses

The pyrolysis mechanics of Phenolic Impregnated Carbon Ablators (PICA) makes it a valued material for use in thermal protection systems for spacecraft atmospheric re-entry. The present study of the interaction of pyrolysis gases and char with plasma gases in the boundary layer over PICA and its substrate, FiberForm, extends previous work on this topic that has been done in the UVM 30 kW Inductively Coupled Plasma (ICP) Torch Facility. Exposure of these material samples separately to argon, nitrogen, oxygen, air, and carbon dioxide plasmas, and combinations of said test gases provides insight into the evolution of the pyrolysis gases as ...


Power And Langmuir Probe Measurements Of H2 Rf Plasma, Alexander A. Stowell May 2016

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, John Carlson May 2016

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.


An Investigation Into Nuclear Fusion Energy Through The 2d Numerical Simulation Of Mhd Instabilities, Dempsey Rodgers Apr 2016

An Investigation Into Nuclear Fusion Energy Through The 2d Numerical Simulation Of Mhd Instabilities, Dempsey Rodgers

Mathematics, Engineering and Computer Science Undergraduate Theses

We have studied a tokamak’s fusing medium, plasma, through a computational study of the magnetohydrodynamic equations. Throughout this study we have analyzed many plasma characteristics, like magnetic tension and compression, diffusion, advection, and viscosity. This study has shown that we can correct for naturally occurring magnetic compression and tension by implementing strong initial magnetic fields both inside and outside the reactor. We determined the magnitudes and shapes of these magnetic fields through research and mathematical modeling. The magnitudes of these fields were optimized using a numeric shooting method to increase magnetic confinement time. The best magnetic confinement regime found ...


Intensity Control Of Dielectric Barrier Discharge Filaments, Matthew Crawford Paliwoda Jan 2016

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 ...


Fully Kinetic Ion Models For Magnetized Plasma Simulations, Benjamin Sturdevant Jan 2016

Fully Kinetic Ion Models For Magnetized Plasma Simulations, Benjamin Sturdevant

Applied Mathematics Graduate Theses & Dissertations

This thesis focuses on the development of simulation models, based on fully resolving the gyro-motion of ions with the Lorentz force equations of motion, for studying low-frequency phenomena in well-magnetized plasma systems. Such models, known as fully kinetic ion models, offer formal simplicity over higher order gyrokinetic ion models and may provide an important validation tool or replacement for gyrokinetic ion models in applications where the gyrokinetic ordering assumptions are in question. Methods for dealing with the added difficulty of resolving the short time scales associated with the ion gyro-motion in fully kinetic ion models are explored with the use ...


The Development Of A Cryogenic Chamber To Study Hypervelocity Dust Bombardment Of Ice And Icy Regolith, Andrew Nelson Jan 2016

The Development Of A Cryogenic Chamber To Study Hypervelocity Dust Bombardment Of Ice And Icy Regolith, Andrew Nelson

Undergraduate Honors Theses

The evolution of many interplanetary icy surfaces, which are prevalent throughout the solar system, is highly dependent on impact phenomena associated with frequent micrometeoroid (dust) bombardment. A quantifiable experimental investigation of these phenomena is incomplete, however, especially at impact energies similar to those encountered in space. Further efforts are necessary to understand the critical complex chemistry and surface weathering effects that result from hypervelocity dust impacts and to calibrate instruments for future space missions. This work describes the development of a novel cryogenic system that will facilitate the future study of hypervelocity dust impacts into ice and icy regolith. The ...


Improving The Efficiency And Resolution Of Time Of Flight (Tof) Mass Spectrometer For Magnetospheric Applications., Zain Abbas Jan 2016

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 ...


Electrically Induced Plasma, Nate Ashby Nov 2015

Electrically Induced Plasma, Nate Ashby

Physics Capstone Project

No abstract provided.


Kinetic Modeling Of Roll To Roll Rfcvd Plasma, Kudzo S. Ahegbebu, Siva Sashank Tholeti, Alina A. Alexeenko Aug 2015

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 ...


Demagnetization Diagnostics In Collisionless Space Plasma Layers, Jershon Ysrael Lopez May 2015

Demagnetization Diagnostics In Collisionless Space Plasma Layers, Jershon Ysrael Lopez

Theses and Dissertations

A recently proposed set of demagnetization diagnostics [Scudder et al., submitted to Physics of Plasmas, 2015] is related to the preconditions of Guiding Center Theory (GCT) and benchmarked in kinetic particle-in-cell simulations. Specifically, GCT requires that the time and length scales of the field are long compared to the Larmor motion of the particles. When this condition is violated, the particles become demagnetized and the assumptions of magnetohydrodynamics are no longer valid. In this thesis, these diagnostics are applied to different space plasma layers of different length scales.

In the past, proxy diagnostics that are not based on fundamental GCT ...


Experiments In Flowing And Freely Expanding Dusty Plasmas, John Kenneth Meyer May 2015

Experiments In Flowing And Freely Expanding Dusty Plasmas, John Kenneth Meyer

Theses and Dissertations

I study a dusty plasma produced in a DC glow discharge device. The chamber is a stainless steel cylinder 0.6 m in diameter and 0.9 m long. A stainless steel disk 3.2 cm in diameter acts as the anode and the walls act as the cathode. The discharge current is set between 1 - 10 mA and the voltage at the anode between 250 - 300 V. Dust is initially on a tray beneath the anode, and becomes trapped in the anode glow naturally with high discharge current. A secondary cloud can be made at a different location using ...