Plasma and Beam Physics Commons^™

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 …

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, …

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 …

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 …

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 …

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 …

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 …

Spectroscopy Of Highly Charged Ions For Astrophysical And Laboratory Plasma Diagnostics, Yang Yang

All Dissertations

Electron beam ion traps (EBITs) are small-scale laboratory devices that create and trap highly charged ions (HCI) for spectroscopic studies. These devices create plasma conditions resembling astrophysical environments like stellar winds and supernova remnants, providing valuable insights into astrophysical plasma. Theoretical models for such systems require incorporating relativistic and quantum electrodynamics effects, making experimental studies of HCIs essential for benchmarking these theories.

Spectral analysis of astrophysical and laboratory plasma requires understanding the ionization balance. Accurate atomic data, including excitation, ionization, and recombination cross sections, along with precise knowledge of operating conditions such as electron beam density, electron beam energy, and …

Adaptive Plasmonic Metasurfaces For Radiative Cooling And Passive Thermoregulation, Azadeh Didari-Bader, Nooshin M. Estakhri, Nasim Mohammadi Estrakhri

Engineering Faculty Articles and Research

In this work, we investigate a class of planar photonic structures operating as passive thermoregulators. The radiative cooling process is adjusted through the incorporation of a phase change material (Vanadium Dioxide, VO₂) in conjunction with a layer of transparent conductive oxide (Aluminum-doped Zinc Oxide, AZO). VO₂ is known to undergo a phase transition from the “dielectric” phase to the “plasmonic” or “metallic” phase at a critical temperature close to 68°C. In addition, AZO shows plasmonic properties at the long-wave infrared spectrum, which, combined with VO₂, provides a rich platform to achieve low reflections across the …

Comment On “Search For Explanation Of The Neutron Lifetime Anomaly”, F. E. Wietfeldt, R. Biswas, J. Caylor, Bret E. Crawford, M. S. Dewey, N. Fomin, G. L. Greene, C. C. Haddock, S. F. Hoogerheide, H. P. Mumm, J. S. Nico, W. M. Snow, J. Zuchegno

Physics and Astronomy Faculty Publications

We respond to issues raised by Serebrov et al. in a recent paper regarding systematic effects in the beam neutron lifetime experiment performed at NIST. We show that these effects were considered in the original analyses and that our corrections and systematic uncertainties were appropriate. We point out some misunderstandings in the analysis of Serebrov et al. None of the issues raised lead us to alter the value of the neutron lifetime reported.

Apparatus And Instrumentation Design For Investigation Of Surface Impact Effects On Superconductivity, Austin Back

All Theses

The effects of ion irradiation on the physical properties of materials make EBITs an invaluable tool for many scientific and engineering fields. Many experiments rely on the use of these lab setups to test for device reliability, explore surface physics phenomena, and replicate the environment for many physical systems that are not readily accessible. We seek to extend the capabilities of these experiments using the CUEBIT and a new sample holder installed in section 3.

This thesis begins by presenting an overview of the CUEBIT and the basic operations of the equipment. This is followed by a brief explanation of …

Numerical Simulation Of Steady-State Thermal Blooming With Natural Convection, Jeremiah S. Lane, Justin Cook, Martin Richardson, Benjamin F. Akers

Faculty Publications

This work investigates steady-state thermal blooming of a high-energy laser in the presence of laser-driven convection. While thermal blooming has historically been simulated with prescribed fluid velocities, the model introduced here solves for the fluid dynamics along the propagation path using a Boussinesq approximation to the incompressible Navier–Stokes equations. The resultant temperature fluctuations were coupled to refractive index fluctuations, and the beam propagation was modeled using the paraxial wave equation. Fixed-point methods were used to solve the fluid equations as well as to couple the beam propagation to the steady-state flow. The simulated results are discussed relative to recent experimental …

Pulsed Power Neutron Production With Deuterated Polymer Accelerator Targets, Anthony O. Hagey

Theses and Dissertations

This document presents an investigation of the effect of deuterated polyethylene accelerator targets on the neutron fluence from a local mass injection dense plasma focus driven by the United States Naval Research Laboratory’s Hawk pulsed-power generator. After successful production of thin targets, the acquisition of thicker targets, and testing inside Hawk, it was found that the presence of a deuterated polyethylene target increased the neutron fluence. Results suggested that fluence can significantly increase with the presence of a deuterated target vs a nondeuterated target. Additive manufacturing printing was used as a production method in order to determine if deuterated accelerator …