Plasma and Beam Physics Commons^™

Redirection Of Current In A Dense Plasma Focus, Rocky Gonzalez

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Mission Support & Test Services (MSTS) reports that significant amounts of energy needed for generating high energy neutrons is lost within a Dense Plasma Focus between its pinch-end of the anode stalk and at its base near the insulating sleeve. It is their mission and the goal of this research effort to both experimentally and theoretically study current redirection in a DPF during and after pinch dynamics. It is hypothesized that current redirection, due to restrike, behind the dynamic sheath of a dense plasma focus will result in a measurable change in the magnetic field along the longitudinal axis …

Better Light Than Never: A New Radiative Mechanism For Observing Binary Black Holes, Paul Rioles

Graduate Masters Theses

Black holes are notoriously elusive, they are impossible to observe directly, and cur- rent methods of extracting information from behind their cosmic camouflage are both limited in number and experimentally difficult. The scope of this investigation is to ex- plore a proposed novel radiative mechanism for active similar mass binary black holes, affording new observational methods to investigate frequency inspirals of BH mergers. The explored mechanism is a result of each BH’s accretion of the surrounding plasma, creating voids that orbit throughout the plasma. The significant results described in this thesis include expressions for the frequency, power radiated per unit …

Plasma Diagnostics For Anode Cathode Plasmas And High Energy Density Physics On A Linear Transformer Driver, Robert Beattie-Rossberg

Electrical and Computer Engineering ETDs

A twelve-brick air insulated linear transformer driver (LTD) was characterized by charging to voltages ranging from 30 to 70 kV and delivering energy to two separate resistive loads. Various plasma diagnostics were built and fielded with an emphasis on the design, implementation and analysis of a Mach Zehnder interferometer, a moiré deflectometer and a spectroscopy system providing information on the temporal evolution of plasma electron density and atomic composition. Rogowski coils, XRD radiation detectors, framing camera images and time integrated DSLR images are used to further understand load conditions where current data, x ray radiation data, velocity data and instability …

Float Like A Butterfly, Sting Like A Bee!, Kobe D. Rome

SACAD: Scholarly Activities

By injecting an electron into the empty pie* molecular orbital (LUMO) of Amino Acids in gas phase, we measure the Vertical Attachment Energies (VAEs) for the formation of short-lived anion states of these species using electron transmission spectroscopy (ETS). Our ETS study, a first of its kind to measure the VAE for the simplest of proteins, Glycine-Glycine (Gly-Gly), is currently in progress. Based on our previous measurements for several Amino Acids including Glycine, we expect a common range of attachment energy (1.50 – 2.00 eV) for Gly-Gly.

Pulsed-Power Neutron Production With Deuterated Polymer Accelerator Targets, Anthony O. Hagey, Juan J. Manfredi, Whitman T. Dailey, S. L. Jackson, E. R. Kaiser, J, W. Schumer

Faculty Publications

This document presents an investigation of the effect of deuterated accelerator targets on the neutron fluence from a local mass injection dense plasma focus (LMIDPF) driven by the United States Naval Research Laboratory's (NRL) Hawk pulsed-power generator. Deuterated targets were made using two methods: a well-established thin-film casting technique for flat targets and a more novel additive manufacturing technique that allowed targets to be three-dimensional (3D) printed in both flat and conical geometries. These targets were then tested during neutron-producing experiments conducted using Hawk, and theneutron fluences measured for the various target types were compared. Additive manufacturing was used as …

Spectroscopic End Point Detection With An Electron Beam Evaporator, Ryan Mcgraw

University Honors Theses

Spectroscopic end point detection is a common tool used for measuring slope changes in wavelength intensity. Using algorithms able to apply this concept, coatings will be able to be dynamically measured in real time and stopped at the appropriate level to ensure process uniformity. It is currently applied to reductive processes such as etching, where the surface will start to be eaten away, creating a plasma. When the entire amount of a material on a substrate has been eaten away, the plasma will change color as it is beginning to etch a different material. Using a spectrometer, this point where …

Spectroscopic Characterization Of Trivalent Holmium In Liyf4 And Bay2F8 Crystals, Vivian R. Hedberg

Theses and Dissertations

Yttrium-fluoride crystals doped with trivalent holmium are promising laser gain media for mid-infrared laser systems. To accurately model laser systems, a complete optical characterization of the laser gain medium is required. The key modeling parameters were obtained by a spectroscopic investigation of Ho³⁺ in LiYF₄ and BaY₂F₈ crystal hosts. Several important mid-infrared laser transitions were characterized at nominal Ho³⁺ ion concentrations of 10-30 at.%. Polarized emission cross-sections were determined from the fluorescence spectra using the Füchtbauer-Ladenburg method. Polarized absorption cross-sections were obtained using the Integral Reciprocity method. The upper-state lifetimes were measured at room …

Developing A Remote Gamma-Ray Spectra Collection System (Rgscs) By Coupling A High Purity Germanium (Hpge) Detector With A Cosmicguard Background Reduction Device, Zaijing Sun, Krishnakumar Divakar Nangeelil, Haven Searcy

Health Physics and Diagnostic Sciences Faculty Research

Despite being widely used for high-resolution spectral analysis and quantifying low activity in natural samples, the operations and data analysis of High Purity Germanium (HPGe) gamma-ray detectors are seldom fully automated due to the excessive costs associated with commercially available automatic sample changing systems. This paper introduces the design and implementation of a cost-effective, customized remote gamma-ray spectra collection system centered around the HPGe detector coupled to a cosmic-ray veto background reduction device. The HPGe detector system, equipped with a Lynx DSA, is seamlessly integrated with an economically viable automatic sample changer. This sample vial changer is controlled by a …

Next-Generation Alpha Irradiation Platform: Design, Development, And Applications In Radiobiological Research, Harsh Arya

Physics Dissertations - Archive

This dissertation unveils the innovative design, development, and application of a next-generation alpha irradiation platform, specifically crafted for pre-clinical and university-level radiobiological research. Driven by the quest to overcome the inherent limitations of existing alpha particle irradiators, this study explores the profound therapeutic potential of alpha particles in cancer treatment. Known for their exceptional high linear energy transfer (LET), alpha particles exhibit a unique prowess in inducing clustered DNA damage, sparking intriguing possibilities for highly targeted cancer therapies. Yet, their application has been historically constrained by their limited range of biological tissues and the absence of precise delivery systems.

Our …

Experimental Verification And Time-Resolved Bispectral Analysis Of Nonlinear Coupling In The Toroidicity-Induced Alfv´En Eigenmode Spectrum, Gregory Allen Riggs

Graduate Theses, Dissertations, and Problem Reports (ETD)

In magnetically-confined fusion devices, the toroidicity-induced Alfv´en eigenmode (TAE) is a well-studied, weakly stable solution of the linearized ideal magnetohydrodynamic (MHD) equations. Due to intrinsic coupling of poloidal harmonics of the shear Alfv´en wave (SAW) in toroidal geometry, the rotational transform of magnetic field lines modulates the effective index of refraction, ensuring gaps in the so-called “Alfv´en continuum.” Experimental verification of theoretical predictions for various parameters of interest (i.e., frequency, mode structure, instability threshold, etc.) is established in the literature.

We present the first systematic study of TAE-TAE phase coherence in an experimental device, using the DIII-D tokamak. Crucially, nonlinear …

Parametrization Of Fluid Models For Electrical Breakdown Of Nitrogen At Atmospheric Pressure, Shirshak K. Dhali

Electrical & Computer Engineering Faculty Publications

In the transient phase of an atmospheric pressure discharge, the avalanche turns into a streamer discharge with time. Hydrodynamic fluid models are frequently used to describe the formation and propagation of streamers, where charge particle transport is dominated by the creation of space charge. The required electron transport data and rate coefficients for the fluid model are parameterized using the local mean energy approximation (LMEA) and the local field approximation (LFA). In atmospheric pressure applications, the excited species produced in the electrical discharge determine the subsequent conversion chemistry. We performed the fluid model simulation of streamers in nitrogen gas at …

Shock-Discharge Interaction Model Extended Into The Third Dimension, Anna Markhotok

Physics Faculty Publications

This work is an addition to the previously developed two-dimensional model of the shock-plasma interaction, extending it into the third dimension. The model can trace the evolution of the state of the hypersonic flow and the shock front refracted at a thermal discontinuity. The advantages of using the spherical coordinate system for this type of problem include increased transparency in interpreting the solution and a shortened calculation procedure, because all the changes to the front are reduced to one distortion component. Although the vorticity generation triggered at the interface is a consequence of the refraction and tied to the steep …

The Discharge-Induced Polarity-Dependent Propagation Characteristics Of A Strong Shock Wave, Anna Markhotok

Physics Faculty Publications

The specifics of a shock wave propagation down a positive column of a DC discharge in molecular chemically inert gases has been investigated. It was shown that axial gradients caused by the imbalance in the charged particle momentum transfer to the gas molecules can be a reason for the shock velocity dependence on the electric field direction. In pure nitrogen gas, the calculated shock velocity difference of up to 13.5% is in good agreement with the 12% value obtained in the experiment. A returning gas flow organizing in the discharge as a possible mechanism for an extended shock structure and …

Non-Symmetry In The Shock Refraction At A Closed Interface As A Recovery Mechanism, Anna Markhotok

Physics Faculty Publications

The possibility of a shock wave recovery at a discrete closed interface with a heated gas has been investigated. A two-dimensional model applied to conditions of optical discharges featuring spherical, elliptical, and drop-like configurations demonstrated that non-symmetry in the shock refraction contributes to the specific mechanism of recovery other than simply its compensation. Even though the full restoration of the hypersonic flow state does not occur in a strict sense of it, clear reverse changes toward the initial shape of the shock front eventually take place, thus creating an appearance of a full recovery seen in experiments. From analysis of …

Modeling The Dynamics Of Radiation Belt Electrons And Ring Current Protons, Xingzhi Lyu

Graduate Theses, Dissertations, and Problem Reports (ETD)

Earth’s inner magnetosphere is a highly dynamic region with various charged particle populations and current systems. The radiation belts, composed of relativistic electrons and protons, is an environment that can pose significant risks to both spacecraft and humans in space; while the fluctuations of ring current, an electric current flowing around the earth consisting of energetic electrons and ions, can lead to severe disruptions in ground-based electrical systems. In this dissertation, we first modeled the long-term evolution of ring current protons based on the measurements of Van Allen Probes. By implementing a 1D radial diffusion model with charge exchange loss, …

Thermocatalytic Plasma-Assisted Dry Reforming Of Methane Over Ni/Al2o3 Catalyst, Tyler Wong

Seton Hall University Dissertations and Theses (ETDs)

Plasma catalysis is an advantageous approach that combines the effects of plasma with the enhancements of a catalyst. By utilizing a nickel catalyst in the plasma discharge zone of a dielectric barrier discharge (DBD), it can give an enhancement to the electrical field, boost microdischarges, and increase conversion and selectivity rates of CH₄ and CO₂ in the dry reforming of methane (DRM) reaction.

Industrial application of nickel catalysts in DBD Plasma DRM process are limited by poor stability, which is caused by the sintering of active metal particles and coke deposition on the catalyst surface. In this work, …

Nuclear Charge Radius Determination Of Iridium Using Euv Spectroscopy Of Highly Charged Ions, Adam Hosier

All Dissertations

Highly charged ions have emerged on the scene of atomic physics because of their compressed electron cloud enhancing various physical phenomena. While transitions in ions and highly charged ions provide valuable information to different communities, their application in nuclear charge radius measurements becomes increasingly prominent. In this work, we report the extreme ultra-violet spectroscopy of Na-like ions and x-ray spectroscopy of Cu-like, Co-like, and Ni-like ions that explore nuclear charge distributions and the identification of new transitions, respectively.

In the first part of this work, extreme ultra-violet spectroscopy of highly charged ions of Na-like osmium and iridium was performed using …

Detailed Characterization Of A Khz-Rate Laser-Driven Fusion At A Thin Liquid Sheet With A Neutron Detection Suite, Benjamin M. Knight, Connor M. Gautam, Colton R. Stoner, Bryan V. Egner, Joseph R. Smith, Christopher M. Orban, Juan J. Manfredi, Kyle Frische, Michael L. Dexter, Enam A. Chowdury, Anil K. Patnaik

Faculty Publications

We present detailed characterization of laser driven fusion and neutron production (∼10⁵/second) employing 8 mJ, 40fs laser pulses on a thin (< 1 µm) D₂O liquid sheet employing a measurement suite. At relativistic intensity (∼5×10¹⁸W/cm²) and high repetition-rate (1 kHz), the system produces consistent D-D fusion, allowing for consistent neutron generation. Evidence of D-D fusion neutron production is verified b y a measurement suite with three independent detection systems: an EJ-309 organic scintillator with pulse-shape discrimination, a ³He proportional counter, and a set of 36 bubble detectors. Time-of-flight analysis of the scintillator data shows …

Thermal Blooming With Laser-Induced Convection: Radial Basis Function Simulation, Benjamin F. Akers, Steven T. Fiorino, Jonah A. Reeger

Faculty Publications

The propagation of a high energy laser through a nearly stagnant absorbing medium is studied. The absorption values and time scale of the problem are such that the laser induces convective heat currents transverse to the beam. These currents couple to the laser via the refractive index, causing time dependent thermal blooming. A numerical method is developed and applied to the model in [ J. Electromagn. Waves Appl. 33, 96 (2019) ], using radial basis functions for spatial differencing, which allows for irregular point spacings and a wide class of geometries. Both the beam and laser-induced fluid dynamics are …

Strong Ultrafast Demagnetization Due To The Intraband Transitions, G. P. Zhang, Mitsuko Murakami

Symposium Projects

Demagnetization in ferromagnetic transition metals driven by a femtosecond laser pulse is a fundamental problem in solid state physics, and its understanding is essential to the development of spintronic devices. Ab initio calculation of time-dependent magnetic moment in the velocity gauge so far has not been successful in reproducing the large amount of demagnetization observed in experiments. In this work, we propose a method to incorporate intraband transitions within the velocity gauge through a convective derivative in the crystal momentum space. Our results for transition-element bulk crystals (bcc Fe, hcp Co and fcc Ni) based on the time-dependent quantum Liouville …