Digital Commons Network^™

Measuring The Ne/O Ratio For Imap-Lo, Ryan J. Murphy

Honors Theses and Capstones

This paper aims to study if the thinner carbon foils of IMAP-Lo will lead to a better resolution of the C/O ratio and by extension, the Ne/O ratio. This is done by fitting an asymmetric kappa function to the time of flight spectra of both types of carbon foils. The ETU used in the most recent round of IMAP-Lo testing is outfitted with both 2ug/cm^2 and 1ug/cm^2 foils letting us create a model relating how the spectra change in response to different foil thickness. Using this model and validating it against test results, we simulate what we would expect to …

Development And Implementation Of A Pressure-Temperature Control System For The Physical Vapor Deposition Of Copper And Niobium From A Molybdenum Filament In The Development Of Superconducting 3d Printed Rf Cavity Particle Accelerators, Chandler J. Fleuette

Honors Theses and Capstones

This report covers the development of the pressure-temperature control system used in the production of small superconducting RF cavities for particle accelerators. To test the validity of the created program, a model for the process was created and tested. The model was used to fine tune the control system before integrating it into the lab. The end goal of the control system is to measure the pressure inside of a deposition vacuum chamber, convert that pressure to a temperature, and use that temperature in tandem with a PID controller to control the current passing though a molybdenum filament which is …

Quantifying Electron Precipitation In The Van Allen Radiation Belts, Timothy Raeder

Honors Theses and Capstones

The spatial and temporal distribution of high energy electron precipitation from the Van Allen radiation belts is not currently well-understood. The FIREBIRD-II mission (2015-present) and the Van Allen Probes (2012-2019) provide a unique opportunity to examine the behaviors and drivers of high energy electron precipitation. This study quantifies electron precipitation observed by FIREBIRD-II as a function of radial distance (L-shell), magnetic local time (MLT), hemisphere, and geomagnetic indices (Kp). Electron precipitation was observed to peak at L-shell 4.5-5. Regions of elevated electron precipitation were identified at L-shell 4-6 at dawn (MLT 6-9) and dusk (MLT 15-21). Hemisphere filtering indicated very …

The Effect Of Ionospheric Conductivity On Magnetospheric Dynamics, Benjamin Joseph Jensen

Doctoral Dissertations

The connection between ionospheric conductivity and the dynamics of the magnetosphere was investigated, using several methods to change the ionospheric conductivity and then study the resultant changes to the magnetosphere. Computer simulations of the Earth's geospace environment were utilized using OpenGGCM coupled with an ionosphere model CTIM and a ring current model RCM.

Three methods were used to modify ionospheric conductivity. The incoming particle precipitation was modified by several orders of magnitude $\alpha=.01,.1,1,10$, the ionospheric conductivity was increased or decreased by factors $\beta=.25, .5, 1, 2,$ and $4$, and for the last method differing values of $F_{10.7}$, $70,110, 150, 200,$ …

Design And Performance Of A 1 Meter Scale Horizontal Axis Wind Turbine Model, Samuel Babineau Cole

Master's Theses and Capstones

A research wind turbine of one-meter diameter was designed for the use in the UNH Flow Physics Facility (FPF), a large flow physics quality boundary layer wind tunnel. The turbine design was carried out as an aero-servo model of the NREL 5MW reference turbine, with some modifications. The turbine is used to obtain data for multiscale wake model verification and validation, including wake data over long distances downstream. Blockage in the FPF test section is 4.8% based on rotor swept area.

The rotor was designed using blade element momentum theory based on the S801 airfoil. The optimal blade chord was …

Structure And Mechanical And Tribological Properties Of Magnetron Sputter Deposition Of Stainles-Steel Nitride And Carbide Thin Films With Transition Metal Additives, Faisal Alresheedi

Doctoral Dissertations

Since the initial discovery of the S-phase in 1985, understanding the structural nature of this phase and the anomalous shift of the (200) diffraction peaks has been a challenging problem. Austenitic stainless steels, ternary Fe–Cr–Ni alloys, like AISI 304, demonstrate excellent corrosion resistance and relatively good levels of toughness and strength. For this reason, they are widely used engineering materials in areas such as aerospace, construction buildings, piping, telecommunications, chemical and petrochemical applications. However, stainless steels have a relatively low hardness, and this leads to a poor wear resistance, resulting in a short lifetime that limits its use in industrial …

Interplanetary Transport Of Solar Energetic Particles, Gen Li

Doctoral Dissertations

Solar energetic particles (SEPs) are high-energy ions and electrons originating at or near the Sun. The energies of these particles extend from solar wind energies up to ∼10 GeV for ions and ∼100 MeV for electrons. This dissertation employs primarily analytical tools to accomplish three research tasks related to the propagation of SEPs from the lower solar corona to 1 AU: (1) developing a transport model based on the focused transport equation to illustrate and predict the spatial and pitch-angle distribution of the nearly scatter-free beam-like protons observed during the onset phase of the so-called ground level events; (2) constructing …

Atomic Structure Studies Of 2d Materials And Advancement Of Dynamical Leem/Uleed-Iv Analysis, Zhongwei Dai

Doctoral Dissertations

Two-dimensional (2D) materials have attracted much attention as an emerging category of materials over the past decade due to their novel mechanical, optical and electronic properties with many potential applications in photovoltaics, photo-catalysts, and modern electronics. However, the detailed atomic structural information has been rarely experimentally investigated due to the following difficulties: (i) the limited sample size of 2D materials prepared through mechanical exfoliation of a few µm, and (ii) the easy oxidation and surface instability of various 2D materials under high energy probing techniques. Selected area low-energy electron diffraction analysis (µLEED-IV performed in a low-energy electron microscopy (LEEM) system, …

Response Of The Pui Distribution To Variable Solar Wind Conditions, Jonathan Slade Bower

Master's Theses and Capstones

We present the first systematic analysis to determine pickup ion (PUI) cutoff speed variations, during general compression regions identified by their structure, shock fronts, and times of highly variable solar wind (SW) speed or magnetic field strength. This study is motivated by the attempt to remove or correct for these effects on the determination of the longitude of the interstellar neutral gas flow from the flow pattern related variation of the PUI cutoff with ecliptic longitude. At the same time, this study sheds light on the physical mechanisms that lead to energy transfer between the SW and the embedded PUI …

Fine Structure In The Ionosphere, Bruce Fritz

Doctoral Dissertations

Fine-scale structure plays an important role in the ionosphere and can be used to learn new information about a whole host of phenomena. This dissertation presents three separate studies of fine-scale ionospheric phenomena. First, morphological behavior of black aurora with pulsating aurora provides new information on how pulsating aurora interacts with the ionosphere. Black curls in conjunction with pulsating aurora indicate diverging electric fields in and above the ionosphere, which is visual evidence that black aurora is part of an ionospheric feedback mechanism. Next, a year of magnetometer observations in the extremely-low frequency (ELF) range placed new physical constraints on …

The Proton Spin Structure Function G2p At Low Momentum Transfer, Tobias Badman

Doctoral Dissertations

Over the past several decades Jefferson Lab National Accelerator Facility has proven to be extremely successful in its endeavor to study the polarized structure of nucleons. Measurements of these nucleon structure functions have proven to be powerful tools in testing and understanding a number of effective theories of QCD. The neutron spin structure functions, g1n and g2n, and the proton spin structure function, g1p, have been measured to very high precision over a wide kinematic range. However, the second proton structure function, g2p, remained largely unmeasured. The primary goal of Jefferson Lab Hall A experiment E08-027 was to perform an …

The G2p Experiment: A Measurement Of The Proton's Spin Structure Functions, Ryan Zielinski

Doctoral Dissertations

The E08-027 (g2p) experiment measured the spin structure functions of the proton at Jefferson Laboratory in Newport News, Va. Longitudinally polarized electrons were scattered from a transversely and longitudinally polarized solid ammonia target in Jefferson Lab's Hall A, with the polarized NH₃ acting as an effective proton target. Focusing on small scattering angle events at the electron energies available at Jefferson Lab, the experiment covered a kinematic phase space of 0.02 GeV² < Q² < 0.20 GeV² in the proton's resonance region. The spin structure functions, g₁^p(x,Q²) and g₂^p(x,Q²) , are …

A Dynamical-Systems Approach To Understanding Turbulence In Plane Couette Flow, Mimi Szeto

Doctoral Dissertations

Dynamical systems theory is used to understand the dynamics of low-dimensional spatio-temporal chaos. Our research aimed to apply the theory to understanding turbulent fluid flows, which could be thought of as spatio-temporal chaos in a very-high dimensional space. The theory explains a system's dynamics in terms of the local dynamics of its periodic solutions; these are the periodic orbits in state space. We considered the development of a model for the dynamics of plane Couette flow based on the theory. The proposed model is essentially a set of low-dimensional models for the local dynamics of the periodic orbits of the …

Modeling And Observation Of He+ Pickup Ions In The Inner Heliosphere, Junhong Chen

Doctoral Dissertations

Interstellar pickup ions constitute a charged particle population that originates from interstellar neutrals inside the heliosphere. They are produced by photoionization, charge exchange with solar wind ions, and electron impact ionization (EI). Once ionized, they are picked up by the interplanetary magnetic field (IMF) and rapidly swept outward with the solar wind. Typically, pickup ion distributions have been described in terms of a velocity distribution function that evolves through fast pitch angle scattering followed by adiabatic cooling during radial transport in the reference frame of the solar wind [e.g., Vasyliunas & Siscoe, 1976, VS76 hereafter].

In the VS76 model, the …

The Study Of Magnetotail Dynamics And Their Ionospheric Signatures Using Magnetohydrodynamic Simulation Model: Openggcm, Banafsheh Ferdousi Shahandashti

Doctoral Dissertations

In-situ measurements in the magnetotail are sparse and limited to single points. In the ionosphere, on the other hand, there is a broad range of observations, including magnetometers, aurora imagers, and radars . Since the ionosphere is the mirror of the plasmasheet, it can be used as a monitor of the magnetotail dynamics. Thus, it is of great importance to understand the coupling process between the ionosphere and the magnetosphere in order to interpret the ionosphere and ground observations properly. In this dissertation, the global magnetohydrodynamic simulation model, OpenGGCM model, is used to investigate two of such coupling processes. The …

A Study Of Reconnection Poleward Of The Cusp: Cluster And Polar, Fathima M. Muzamil

Doctoral Dissertations

Asymmetries in plasma density and the presence of a guide field significantly alter the structure of the ion diffusion region (IDR) in symmetric, collisionless reconnection. These features have been shown by numerical simulations under moderate density asymmetries (~10), and theoretical analyses. However, very few studies have addressed these issues with in-situ observations, particularly at high magnetic latitudes. By the structure of the IDR we refer to features such as the non-colocation of the X-line and stagnation line, the distortion of the Hall magnetic and electric fields, outflow speed, outflow density etc. We have compiled a collection of Cluster crossings of …

Nonlinear Evolution Of Mirror Instability In The Earth's Magnetosheath In Pic Simulations, Narges Ahmadihojatabad

Doctoral Dissertations

Mirror modes are large amplitude non-propagating structures frequently observed in the magnetosheath and they are generated in space plasma environments with proton temperature anisotropy of larger than one. The proton temperature anisotropy also drives the proton cyclotron instability which has larger linear growth rate than that of the mirror instability. Linear dispersion theory predicts that electron temperature anisotropy can enhance the mirror instability growth rate while leaving the proton cyclotron instability largely unaffected. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than …

"Smoking-Gun" Observables Of Magnetic Reconnection: Spatiotemporal Evolution Of Electron Characteristics Throughout The Diffusion Region, Jason Shuster

Doctoral Dissertations

How does magnetic reconnection happen in a collisionless plasma? Knowledge of electron-scale dynamics is necessary to answer this outstanding question of plasma physics. Based on fully kinetic particle-in-cell (PIC) simulations of symmetric reconnection, the spatiotemporal evolution of velocity distribution functions in and around the electron diffusion region (EDR) elucidates how electrons are accelerated and heated by the cooperating reconnection electric and normal magnetic fields. The discrete, triangular structures characteristic of EDR distributions rotate and gyrotropize in velocity space as electrons remagnetize, forming multicomponent arc and ring structures. Further downstream, exhaust electrons are found to exhibit highly structured, time-dependent anisotropies that …

Quantifying The Role Of The Seed Population In Radiation Belt Dynamics, Alexander Boyd

Doctoral Dissertations

The dynamics of the radiation belts depend on a delicate balance of source and loss processes. One such source process that has been shown to be effective is local acceleration, where 10s-100s keV seed electrons are accelerated via wave-particle interactions up to energies >1 MeV. Historically, much of the focus of radiation belt research has been on the dynamics of these >1 MeV electrons, and the role and importance of the seed electrons has been largely overlooked. In this thesis, we use phase space density calculated using data from the Van Allen Probes, to directly investigate seed population for a …

Analyzing The Interstellar Neutral He Bulk Flow Parameters With Ibex-Lo, Trevor Leonard

Doctoral Dissertations

Our Sun is immersed in a local galactic environment which is composed of a warm, dilute, and partially ionized gas. Due to the Sun’s motion relative to this environment, the interstellar neutral (ISN) gas flows through the heliosphere providing the opportunity to perform in-situ observations of the ISN gas from Earth’s orbit. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. The first observations of ISN H, O, and Ne were recorded by IBEX, along with the most detailed observation of ISN He. Since He …

Small Solar Wind Transients 1995 - 2014: Properties, Modeling, And Effects On The Magnetosphere, Wenyuan Yu

Doctoral Dissertations

Using case studies and statistical analysis on a large data sample we investigate properties of small solar wind transients (STs) and discuss their modeling. The observations are from the Wind and STEREO spacecraft. By "small" we mean a duration of 0.5-12 hours. We do not restrict ourselves to magnetic flux ropes. Having arrived at a definition based on an extension of previous work, we apply an automated algorithm to search for STs. In one chapter we focus on the solar activity minimum years 2007-2009. We find an average ST duration of ~4.3 hours, with 75% lasting less than 6 hours. …

Molecular Dynamics Simulations Of A Pentacene Derivative On Gold Surfaces In The Quantum Mechanical And Classical Mechanics Frameworks, Ryan Allen Miller

Master's Theses and Capstones

With increasing potential to serve as a basis for constructing organic photovoltaic de- vices, the directed self-assembly of small organic molecules on metal substrates provides an interesting new method of bottom-up device building. By utilizing the qualities inherent in the substrate and molecules, one can manipulate surface topology to create functional layers of molecules in a desired configuration. However, tailoring these organic layers in a useful way requires detailed analysis of the substructure characteristics. With top-down visualization approaches like Scanning Tunneling Microscopy (STM) pro- viding a limited view of assembled layer structural characteristics, molecular dynamics sim- ulations must be employed …

Nonlinear Waves On A String With Inhomogeneous Properties, Robert Arredondo

Doctoral Dissertations

Nonlinear waves on an infinite string with a rapid change in properties at one location are treated. The string is an idealized version of more complex configurations in both fluids and solids. This idealized version treats the property change as an interface with a discontinuity in properties. Packets of waves are then considered with a reduced model, here a set of nonlinear Schr¨odinger (NLS) equations. The stress and the displacement must both be matched at the interface, resulting in dynamic and kinematic interfacial conditions. The dynamic condition produces an inhomogeneous effect that cannot be treated successfully with separation-of-variables. This inhomogeneity …

The Directed Molecular Self-Assembly Of A Novel Pentacene Derivative On Gold Surfaces: An Experimental And Computational Study, Amanda Margaret Larson

Doctoral Dissertations

Understanding electronic devices down to the atomic scale is essential for the development of novel organic molecule based nanotechnologies. Utilizing scanning tunneling microscopy (STM), new organic molecules can be imaged to understand their structural and electronic properties at the molecular level. 5,6,7-trithiapentacene-13-one (TTPO) is a promising organic semiconductor with potential applications in high temperature photovoltaic devices as an electron donor. My STM investigation of TTPO on the close-packed stepped Au(788) surface reveals interesting nanoscale surface structures ranging from molecular chains at low coverage to an ordered self-assembled monolayer. I have utilized density functional theory (DFT) to further probe this unique …

A Study Of Interplanetary Shock Geoeffectiveness Controlled By Impact Angles Using Simulations And Observations, Denny Oliveira

Doctoral Dissertations

In this dissertation, we study the influence of interplanetary (IP) shock impact angles in the IP shock geoeffectiveness focusing on simulations and observations. In our simulations, we use OpenGGCM global MHD code to study the nightside magnetospheric, magnetotail, and ionospheric responses to IP fast forward shocks. Three cases are presented in this study: two inclined oblique shocks, hereafter IOS-1 and IOS-2, where the latter has a Mach number twice stronger than the former. Both shocks have impact angles of 30$^o$ in relation to the Sun-Earth line. Lastly, we choose a frontal perpendicular shock, FPS, whose shock normal is along the …

The Study Of Ionospheric Response To Precipitation Using Sounding Rocket Observations, Ian James Cohen

Doctoral Dissertations

Understanding the role that the ionosphere plays in phenomena such as the development of auroral arcs and ion outflow is basic to the investigation of these processes and critical to the advancement of the broader study of magnetosphere-ionosphere coupling. Sounding rockets present an optimal platform for such studies, allowing low-cost access to altitudes that are difficult to reach by other means. Additionally, these measurements are key to validating current models and furthering understanding of the near-Earth space environment. This thesis highlights two particular rocket-borne instruments that measure electron populations in the ionosphere: the Electron Retarding Potential Analyzer (ERPA) and the …

A Supercell, Bloch Wave Method For Calculating Low-Energy Electron Reflectivity With Applications To Free-Standing Graphene And Molybdenum Disulfide, John Francis Mcclain

Doctoral Dissertations

This dissertation reports on a novel theoretical and computational framework for calculating low-energy electron reflectivities from crystalline surfaces and its application to two layered systems of two-dimensional materials, graphene and molybdenum disulfide. The framework provides a simple and efficient approach through the matching of a small set of Fourier components of Bloch wave solutions to the Schrodinger Equation in a slab-in-supercell geometry to incoming and outgoing plane waves on both sides of the supercell. The implementation of this method is described in detail for the calculation of reflectivities in the lowest energy range, for which only specular reflection is allowed. …

The Synthesis And Characterization Of Iron Nanoparticles, Tyler Paul Bennett

Master's Theses and Capstones

Nanoparticle synthesis has garnered attention for technological applications for catalysts, industrial processing, and medical applications. The size ranges for these is in the particles nanostructural domain. Pure iron nanoparticles have been of particular interest for their reactivity and relative biological inertness. Applications include cancer treatment and carrying medicine to a relevant site. Unfortunately, because of their reactivity, pure iron nanoparticles have been difficult to study. This is because of their accelerated tendency to form oxides in air, due to the increased surface area to volume ratio. Using synthesis processes with polyphenols or long chain amines, air stable iron nanoparticles have …

Estimating Proximity To The Asymmetric Reconnection X-Line, Matthew Argall

Doctoral Dissertations

Magnetic reconnection is a process that changes magnetic topology, allows plasma transport across boundaries, and converts field potential energy to particle kinetic energy. All of these processes are tied to the X-line, or site of reconnection, yet current methods of locating the reconnection site either do not uniquely identify the the X-line or have not been tested when asymmetries in field strength and plasma density and temperature are present. Furthermore, identification of spacial structures (such as the X-line) as they traverse satellites is limited by hardware constraints. This thesis proposes a new method of locating the reconnection site for asymmetric …

Streamline Geometry Analysis Of Turbulent Fluid Flows, Michael Dunstan

Master's Theses and Capstones

Energy in turbulent flows is transported down coherent vortical structures of different shapes and sizes. Experiments have shown that the vortical structures contain field lines that are curved in nature. Several procedures have been investigated to determine the size and location of the coherent vortical motions, as of yet there has not been a widely accepted method that exactly depicts these structures. Among the current methods of determining the coherent features of the flow, structures determined by the second largest eigenvalue of the symmetric part of the gradient of the Navier-Stokes equation has received recent attention. Another method proposed is …