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Physics

Radiation

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Full-Text Articles in Physical Sciences and Mathematics

Measurement Of Additional Radiation In The Initial-State-Radiation Processes E+E-Μ+Μ- Y And E+E-+- Y At Babar, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu. G. Kolomensky, M. Fritsch, H. Koch, R. Cheaib, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, E. A. Kozyrev, Milind Purohit, Et. Al. Nov 2023

Measurement Of Additional Radiation In The Initial-State-Radiation Processes E+E- →Μ+Μ- Y And E+E- → ℼ+ℼ- Y At Babar, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu. G. Kolomensky, M. Fritsch, H. Koch, R. Cheaib, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, E. A. Kozyrev, Milind Purohit, Et. Al.

Faculty Publications

A dedicated measurement of additional radiation in e+e → µ+µγ and e+eπ+πγ initial-state-radiation events is presented using the full BABAR data sample. For the first time results are presented at next-to- and next-to-next-to-leading order, with one and two additional photons, respectively, for radiation from the initial and final states. Comparison with predictions from PHOKHARA and AFKQED Monte Carlo generators is performed, revealing discrepancies in the one-photon rates and angular distributions for the former. This disagreement has a negligible effect on the BABAR measurement of …


Trumpet Directivity From A Rotating Semicircular Array, Samuel D. Bellows, Joseph E. Avila, Timothy W. Leishman Sep 2023

Trumpet Directivity From A Rotating Semicircular Array, Samuel D. Bellows, Joseph E. Avila, Timothy W. Leishman

Directivity

The directivity function of a played musical instrument describes the angular dependence of its acoustic radiation and diffraction about the instrument, musician, and musician’s chair. Directivity influences sound in rehearsal, performance, and recording environments and signals in audio systems. Because high-resolution, spherically comprehensive measurements of played musical instruments have been unavailable in the past, the authors have undertaken research to produce and share such data for studies of musical instruments, simulations of acoustical environments, optimizations of microphone placements, and other applications. The authors acquired the data from repeated chromatic scales produced by a trumpet played at mezzo-forte in an anechoic …


Precise Determination Of Charge Distributions In Electron Irradiated Polymers Via Pulsed Electroacoustic Measurements With Applications To Spacecraft Charging, Zachary Gibson Aug 2023

Precise Determination Of Charge Distributions In Electron Irradiated Polymers Via Pulsed Electroacoustic Measurements With Applications To Spacecraft Charging, Zachary Gibson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Understanding how charge builds up and moves around in materials that are highly insulating, such as dielectrics, is important for many applications from power transmission to spacecraft charging. The leading cause of issues in spacecraft due to interactions with the space environment is spacecraft charging. That is, the accumulation of charge on insulating materials leads to arcing and sparking aboard the spacecraft. The most critical charging occurs due to electrons in a particular energy range of 10-50 keV. Electrons with these energies can travel 1’s to 10’s of microns into relevant materials. To measure where the charge is embedded and …


Fabrication, Measurements, And Modeling Of Semiconductor Radiation Detectors For Imaging And Detector Response Functions, Corey David Ahl May 2023

Fabrication, Measurements, And Modeling Of Semiconductor Radiation Detectors For Imaging And Detector Response Functions, Corey David Ahl

Doctoral Dissertations

In the first part of this dissertation, we cover the development of a diamond semiconductor alpha-tagging sensor for associated particle imaging to solve challenges with currently employed scintillators. The alpha-tagging sensor is a double-sided strip detector made from polycrystalline CVD diamond. The performance goals of the alpha-tagging sensor are 700-picosecond timing resolution and 0.5 mm spatial resolution. A literature review summarizes the methodology, goals, and challenges in associated particle imaging. The history and current state of alpha-tagging sensors, followed by the properties of diamond semiconductors are discussed to close the literature review. The materials and methods used to calibrate the …


Effectiveness Of Multilayer Graded-Z Forms Of Radiation Shielding, Brinley Packer Apr 2023

Effectiveness Of Multilayer Graded-Z Forms Of Radiation Shielding, Brinley Packer

Physics Capstone Projects

This study explored how different forms of radiation shielding were more or less effective than standard single-layer shielding. Beta and gamma radiation sources were used and measured using a Geiger counter to determine how well the various forms of shielding protect against the radiation. The shielding effectiveness of standard homogeneous materials (e.g., graphite, carbon/epoxy composites, aluminum, and lead) of various thicknesses for different radiation sources was measured to provide standards for comparison. Once a basis of effective shielding was established, the study can go into greater depth into how to use shielding materials to be more effective, to better shield …


Gamelan Gong Directivity Dataset, Samuel D. Bellows, Dallin T. Harwood, Kent L. Gee, Micah R. Shepherd Jan 2023

Gamelan Gong Directivity Dataset, Samuel D. Bellows, Dallin T. Harwood, Kent L. Gee, Micah R. Shepherd

Directivity

No abstract provided.


Full Treatment Of The Thrust Distribution In Single Inclusive E⁺E⁻ → H X Processes, M. Boglione, Andrea Simonelli Jan 2023

Full Treatment Of The Thrust Distribution In Single Inclusive E⁺E⁻ → H X Processes, M. Boglione, Andrea Simonelli

Physics Faculty Publications

Extending the transverse momentum dependent factorization to thrust dependent observables entails a series of difficulties, ultimately associated to the behavior of soft radiation. As a consequence, the definition of the transverse momentum dependent functions has to be revised, while preserving (and possibly extending) their universality properties. Moreover, the regularization of the rapidity divergences generates non trivial correlations between rapidity and thrust. In this paper, we show how to deal with these correlations in a consistent treatment of the thrust dependence of e+eh X cross section, where the hadron transverse momentum is measured with respect to …


Liposome Formulation For Tumor-Targeted Drug Delivery Using Radiation Therapy, Daniel Fologea Oct 2022

Liposome Formulation For Tumor-Targeted Drug Delivery Using Radiation Therapy, Daniel Fologea

Physics Faculty Publications and Presentations

Targeted delivery of drugs or other therapeutic agents through internal or external triggers has been used to control and accelerate the release from liposomal carriers in a number of studies, but relatively few utilize energy of therapeutic X-rays as a trigger. We have synthesized liposomes that are triggered by ionizing radiation (RTLs) to release their therapeutic payload. These liposomes are composed of natural egg phosphatidylethanolamine (PE), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and 1,2-disteroyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] (DSPE-PEG-2000), and the mean size of the RTL was in the range of 114 to 133 nm, as measured by nanoparticle tracking analysis (NTA). The trigger mechanism …


Computational Models To Detect Radiation In Urban Environments: An Application Of Signal Processing Techniques And Neural Networks To Radiation Data Analysis, Jose Nicolas Gachancipa Jul 2022

Computational Models To Detect Radiation In Urban Environments: An Application Of Signal Processing Techniques And Neural Networks To Radiation Data Analysis, Jose Nicolas Gachancipa

Beyond: Undergraduate Research Journal

Radioactive sources, such as uranium-235, are nuclides that emit ionizing radiation, and which can be used to build nuclear weapons. In public areas, the presence of a radioactive nuclide can present a risk to the population, and therefore, it is imperative that threats are identified by radiological search and response teams in a timely and effective manner. In urban environments, such as densely populated cities, radioactive sources may be more difficult to detect, since background radiation produced by surrounding objects and structures (e.g., buildings, cars) can hinder the effective detection of unnatural radioactive material. This article presents a computational model …


Electron-Positron Annihilation Lifetime Spectroscopy Of Mgo And Aluminum-Doped Mgo, Elise Liebow Mar 2022

Electron-Positron Annihilation Lifetime Spectroscopy Of Mgo And Aluminum-Doped Mgo, Elise Liebow

Honors Theses

Radiation is a form of energy that can damage materials at an atomic level. This has implications for the mobility of radioactive waste through containment materials. We are characterizing atomic defects in materials by using Electron-Positron Annihilation Lifetime Spectroscopy (EPALS). When an electron and positron come into contact with each other, they annihilate and release two antiparallel 511-keV gamma rays. In a pristine crystalline sample, positrons can easily annihilate with electrons, but in a sample with vacancies/defects in the crystal structure, positrons take longer to annihilate. Therefore, the more vacancies in a sample, the longer the average lifetime of a …


Efficient Neuromorphic Algorithms For Gamma-Ray Spectrum Denoising And Radionuclide Identification, Merlin Phillip Carson Sep 2021

Efficient Neuromorphic Algorithms For Gamma-Ray Spectrum Denoising And Radionuclide Identification, Merlin Phillip Carson

Dissertations and Theses

Radionuclide detection and identification are important tasks for deterring a potentially catastrophic nuclear event. Due to high levels of background radiation from both terrestrial and extraterrestrial sources, some form of noise reduction pre-processing is required for a gamma-ray spectrum prior to being analyzed by an identification algorithm so as to determine the identity of anomalous sources. This research focuses on the use of neuromorphic algorithms for the purpose of developing low power, accurate radionuclide identification devices that can filter out non-anomalous background radiation and other artifacts created by gamma-ray detector measurement equipment, along with identifying clandestine, radioactive material.

A sparse …


Proximal Policy Optimization For Radiation Source Search, Philippe Erol Proctor Aug 2021

Proximal Policy Optimization For Radiation Source Search, Philippe Erol Proctor

Dissertations and Theses

Rapid localization and search for lost nuclear sources in a given area of interest is an important task for the safety of society and the reduction of human harm. Detection, localization and identification are based upon the measured gamma radiation spectrum from a radiation detector. The nonlinear relationship of electromagnetic wave propagation paired with the probabilistic nature of gamma ray emission and background radiation from the environment leads to ambiguity in the estimation of a source's location. In the case of a single mobile detector, there are numerous challenges to overcome such as weak source activity, multiple sources, or the …


X Radiation Dose Monitoring For Adolescent And Adult Patients In Selected Health Care Environment Related Places, Kevin Riandi Jul 2021

X Radiation Dose Monitoring For Adolescent And Adult Patients In Selected Health Care Environment Related Places, Kevin Riandi

Journal of Environmental Science and Sustainable Development

A study on patient absorption dose according to age group was carried out. The amount of absorbed A study on patient absorption dose according to age group was carried out. The amount of absorbed dose of X-ray radiation affect the body cells. Health care hospitals such as clinics, environments that use ionizing radiation. Based on the procedure for using ionizing radiation for medical purposes, the Indonesian Nuclear Energy Supervisory Agency recommends monitoring radiation doses for health workers on health service environment. Likewise with the patient, because the patient is directly exposed to the ionizing radiation. Some researh explained that the …


Comparing Radiation Shielding Potential Of Liquid Propellants To Water For Application In Space, John Czaplewski Mar 2021

Comparing Radiation Shielding Potential Of Liquid Propellants To Water For Application In Space, John Czaplewski

Master's Theses

The radiation environment in space is a threat that engineers and astronauts need to mitigate as exploration into the solar system expands. Passive shielding involves placing as much material between critical components and the radiation environment as possible. However, with mass and size budgets, it is important to select efficient materials to provide shielding. Currently, NASA and other space agencies plan on using water as a shield against radiation since it is already necessary for human missions. Water has been tested thoroughly and has been proven to be effective. Liquid propellants are needed for every mission and also share similar …


Using Ai For Management Of Field Emission In Srf Linacs, A. Carpenter, P. Degtiarenko, R. Suleiman, C. Tennant, D. Turner, L. S. Vidyaratne, Khan Iftekharuddin, Md. Monibor Rahman Jan 2021

Using Ai For Management Of Field Emission In Srf Linacs, A. Carpenter, P. Degtiarenko, R. Suleiman, C. Tennant, D. Turner, L. S. Vidyaratne, Khan Iftekharuddin, Md. Monibor Rahman

Electrical & Computer Engineering Faculty Publications

Field emission control, mitigation, and reduction is critical for reliable operation of high gradient superconducting radio-frequency (SRF) accelerators. With the SRF cavities at high gradients, the field emission of electrons from cavity walls can occur and will impact the operational gradient, radiological environment via activated components, and reliability of CEBAF’s two linacs. A new effort has started to minimize field emission in the CEBAF linacs by re-distributing cavity gradients. To measure radiation levels, newly designed neutron and gamma radiation dose rate monitors have been installed in both linacs. Artificial intelligence (AI) techniques will be used to identify cavities with high …


Estimates Of Damped Equilibrium Energy Spread And Emittance In A Dual Energy Storage Ring, B. Dhital, Y. S. Derbenev, D. Douglas, A. Hutton, G. A. Krafft, F. Lin, V.S. Morozov, Y. Zhang Jan 2021

Estimates Of Damped Equilibrium Energy Spread And Emittance In A Dual Energy Storage Ring, B. Dhital, Y. S. Derbenev, D. Douglas, A. Hutton, G. A. Krafft, F. Lin, V.S. Morozov, Y. Zhang

Physics Faculty Publications

A dual energy storage ring design consists of two loops at markedly different energies. As in a single-energy storage ring, the linear optics in the ring design may be used to determine the damped equilibrium emittance and energy spread. Because the individual radiation events in the two rings are different and independent, we can provide analytical estimates of the damping times in a dual energy storage ring. Using the damping times, the values of damped energy spread, and emittance can be determined for a range of parameters related to lattice design and rings energies. We present analytical calculations along with …


Аn Optical Study Of Strain Relaxation And Interdiffusion In Znse/Zncdse Quantum Wells Modified By Γ-Irradiation, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov Dec 2020

Аn Optical Study Of Strain Relaxation And Interdiffusion In Znse/Zncdse Quantum Wells Modified By Γ-Irradiation, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov

Scientific Bulletin. Physical and Mathematical Research

If we turn to the literature data, it is known that the degradation of CdZnTe / ZnTe and CdZnSe /ZnSe quantum wells and usually includes two types of processes: (i) fast (as called dynamic, by analogy with the degradation of heterostructures based on A3B5 materials) - germination and propagation of extended defects from a GaAs substrate. This process in CdZnSe / ZnSe is slowed down by various technological methods (treatment of a substrate in sulfur; reduction of a damaged layer in a GaAs substrate; deposition of a GaAs epitaxial buffer layer; use of the concept of compensation of bipolar stresses; …


Effect Of Porosity On Unsteady Mhd Convection Flow Past A Moving Vertical Plate With Ramped Wall Temperature, U. S. Rajput, Mohammad Shareef Dec 2020

Effect Of Porosity On Unsteady Mhd Convection Flow Past A Moving Vertical Plate With Ramped Wall Temperature, U. S. Rajput, Mohammad Shareef

Applications and Applied Mathematics: An International Journal (AAM)

The unsteady MHD convective flow of an electrically conducting fluid embedded in a porous medium along moving infinite vertical plate with ramped wall temperature and radiation in a rotating system is investigated here. The fluid taken is incompressible and viscous. The governing PDE’s of the model are solved by using integral transform method. The analytical solutions for the velocity, concentration and temperature are obtained. The expressions for skin friction, rate of mass transfer and heat transfer near the plate are obtained. The effects of various parameters like porosity of the medium, magnetic field, Soret number, thermal radiation, rotation, radiation and …


Nuclear-Targeted Gold Nanoparticles Enhance The Effects Of Radiation Therapy With And Without Liposomal Delivery, Maureen Aliru Dec 2020

Nuclear-Targeted Gold Nanoparticles Enhance The Effects Of Radiation Therapy With And Without Liposomal Delivery, Maureen Aliru

Dissertations & Theses (Open Access)

Less that 10% of pancreatic cancer patients are eligible for curative resection, and clinical trials evaluating chemoradiation in locally advanced patients with unresectable disease have been largely disappointing. New and creative therapeutic approaches are needed to address the unment need for treatment options. The objective of this thesis is to advance radiosensitization of treatment-resistant densely desmoplastic pancreatic cancer using nanoparticles to surmount biological barriers to effective particle distribution for DNA-targeting.

Clinical translation of radiosensitizing nanoparticles has stalled owing to technical challenges. Current strategies to use AuNPs for radiosensitization require large quantities of gold, kilovoltage x-rays, immediate irradiation after intravenous administration, …


Optical Relaxation Of Defects In Kapton Caused By Irradiation, Ashlan Keeler Swainston Apr 2020

Optical Relaxation Of Defects In Kapton Caused By Irradiation, Ashlan Keeler Swainston

Physics Capstone Projects

Radiation can create atomic-scale defect states in polymers, leading to changes in their optical, electrical and mechanical properties. Recent studies of polymers have shown that these defect states are sensitive to oxygen or air exposure. It is believed that air cause the number of defect states to decrease and the polymers to revert to their original states. However, the time scale of this regression is not known. This experiment quantified the time that it takes one polymer to recover and the extent of said recovery; polymide (PI). In order to study the regression, optical transmission data were taken using a …


Data Analysis Of Large Angle Beamstrahlung Monitor, Samuel Doeg Izaguirre Gamez Jan 2020

Data Analysis Of Large Angle Beamstrahlung Monitor, Samuel Doeg Izaguirre Gamez

Wayne State University Dissertations

The first experimental evidence of large angle beamstrahlung at SuperKEKB is discussed in this Thesis. Beamstrahlung is the tn radiation emitted by particles belonging to one beam when they are accelerated transversely by the electro-magnetic field of the other beam. The properties of the radiation are related to the beam interaction topologyand can be used to optimize the beam-beam collision. This, in turn, makes the machine’s luminosity, and therefore the number of produced events, higher. A device entirely built at WSU, the Large Angle Beamstrahlung Monitor, or LABM, has been deployed in the SuperKEKB accelerator since 2015. A five Institutions …


Evaluation Of The Activity Of Zn-65 Isotope And Radiation Dose Delivered To Drosophila Melanogaster, Wasiu Ajani Erinoso Jan 2020

Evaluation Of The Activity Of Zn-65 Isotope And Radiation Dose Delivered To Drosophila Melanogaster, Wasiu Ajani Erinoso

All Graduate Theses, Dissertations, and Other Capstone Projects

Radioactivity is a natural part of our environment. Ionizing radiation from radioactive materials can affect the life cycle of organisms; sometimes increase the rate of transition between cycle leading to the proliferation of cells as seen in some cancer cells or delay the rate of transition between cell cycle. A NaI detector is essential to determine the activity of a radioactive material. To determine the resolution of NaI detector and the efficiency of the geometry used for this experiment, quality control was done for NaI detector using 22Na reference source. The efficiency of the detector was used to verify the …


Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov Dec 2019

Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov

Scientific Bulletin. Physical and Mathematical Research

The last three decades of the development of solid state physics are characterized by the fact that the main objects of research are increasingly not massive crystals, but thin films, multilayer thin-film systems, conducting filaments and crystallites of small size. Epitaxial films are grown on a substrate of a single crystal of the same or another material. In the first case, the epitaxial layer with the correct technology becomes a natural extension of the substrate. Epitaxial film can be doped with various impurities. To introduce an alloying admixture into the epitaxial film, three methods are used. According to the first …


Relaxation Of Radiation Effects In Polymers, Alexandra Hughlett Nelson Dec 2019

Relaxation Of Radiation Effects In Polymers, Alexandra Hughlett Nelson

Physics Capstone Projects

Radiation can create atomic-scale defect states in polymers, leading to changes in their optical, electrical and mechanical properties. Recent studies of polymers have shown that these defect states are sensitive to oxygen or water exposure. It is believed that oxygen cause the number of defect states to decrease and the polymers to revert to their original states. However, the time scale of this regression is not known. This experiment quantified the time that it takes five polymers to recover and the extent of said recovery; polypropylene (PP), low density polyethylene (LDPE), fluorinated ethylene propylene (FEP), polymide (PI), and poly ether …


Analysis Of Heat Absorption Viscoelastic Exothermic Chemical Reactive Fluid With Temperature Dependent Viscosity Under Bimolecular Kinetic, S. O. Salawu, R. A. Kareem Dec 2019

Analysis Of Heat Absorption Viscoelastic Exothermic Chemical Reactive Fluid With Temperature Dependent Viscosity Under Bimolecular Kinetic, S. O. Salawu, R. A. Kareem

Applications and Applied Mathematics: An International Journal (AAM)

This study examines the boundary layer flow of variable viscosity, incompressible exothermic chemical reactive fluid with thermal radiation and asymmetric convective cooling under Bimolecular kinetic. The viscoelastic fluid flow along a vertical channel in the presence of a thermal buoyancy force and pressure gradient. Rosseland approximation is defined for the thick radiation heat flux in the energy equation with gray radiating liquid, non-scattering but with heat absorbing depending on wavelength. The convective heat exchange with the sorrounding temperature at the channel surface satisfied Newton’s law of cooling. The computational analysis of the dimensionless nonlinear governing equations is obtained using Weighted …


Average Speech Directivity, Samuel D. Bellows, Claire M. Pincock, Jennifer K. Whiting, Timothy W. Leishman Nov 2019

Average Speech Directivity, Samuel D. Bellows, Claire M. Pincock, Jennifer K. Whiting, Timothy W. Leishman

Directivity

Speech directivity describes the angular dependence of acoustic radiation from a talker’s mouth and nostrils and diffraction about his or her body and chair (if seated). It is an essential physical aspect of communication affecting sounds and signals in acoustical environments, audio, and telecommunication systems. Because high-resolution, spherically comprehensive measurements of live, phonetically balanced speech have been unavailable in the past, the authors have undertaken research to produce and share such data for simulations of acoustical environments, optimizations of microphone placements, speech studies, and other applications. The measurements included three male and three female talkers who repeated phonetically balanced passages …


Dynamic Secondary Electron Emission In Rough Composite Materials, Leandro Olano, Maria E. Dávila, John R. Dennison, Petronilo Martín-Iglesias, Isabel Montero Sep 2019

Dynamic Secondary Electron Emission In Rough Composite Materials, Leandro Olano, Maria E. Dávila, John R. Dennison, Petronilo Martín-Iglesias, Isabel Montero

All Physics Faculty Publications

The interaction of ionizing radiation with matter is of critical importance in numerous areas of science and technology like space and vacuum technology and even medicine and biotechnology. Secondary electron emission is a consequence of electron irradiation on materials. We achieve extremely low secondary electron emission yield values smaller than 0.2, even up to incident electron energies ~1 keV, due to an undocumented synergy between neighbouring metal and dielectric domains in composite samples. To investigate this experimental discovery, we propose a simple 3D model where the dielectric and metallic domains are arranged in parallel and interleaved. The proposed surface profile …


Measuring Length Of Electron Bunches With Optics In Lcls-Ii, Nathan Ahn, Alan Fisher Sep 2019

Measuring Length Of Electron Bunches With Optics In Lcls-Ii, Nathan Ahn, Alan Fisher

STAR Program Research Presentations

Since the launch of the LINAC Coherent Light Source (LCLS) in 2009, there have been over 1,000 publications enabling pioneering research across multiple fields. Advances include: harnessing the sun’s light, revealing life’s secrets and aiding drug development, developing future electronics, designing new materials and exploring fusion, customizing chemical reactions, and many more. These discoveries gathered worldwide attention, and now work has begun on a new revolutionary tool, LCLS-II. The LCLS-II will pulse at a million times a second, compared to the 120 pulses from the LCLS. Within the LCLS-II, there are two chicanes, serpentine curves. As the electron beam passes …


Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace Aug 2019

Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace

Theses and Dissertations

Microscale beams of germanium ions were used to target different locations of aluminum galliumnitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) to determine location dependent radiation effects. 1.7 MeV Ge ions were targeted at the gap between the gate and the drain to observe displacement damage effects while 47 MeV Ge ions were targeted at the gate to observe ionization damage effects. Electrical data was taken pre, during, and post irradiation. To separate transient from permanent degradation, the devices were characterized after a room temperature anneal for at least 30 days. Optical images were also analyzed pre and post irradiation. …


Surface Plasmon Induced Enhancement In Selective Laser Melting Processes, Dentcho A. Genov, Raj K. Vinnakota Jun 2019

Surface Plasmon Induced Enhancement In Selective Laser Melting Processes, Dentcho A. Genov, Raj K. Vinnakota

Dentcho Genov

Purpose
Selective laser melting (SLM) is an advanced rapid prototyping or additive manufacturing technology that uses high power density laser to fabricate metal/alloy components with minimal geometric constraints. The SLM process is multi-physics in nature and its study requires development of complex simulation tools. The purpose of this paper is to study – for the first time, to the best of the authors’ knowledge – the electromagnetic wave interactions and thermal processes in SLM based dense powder beds under the full-wave formalism and identify prospective metal powder bed particle distributions that can substantially improve the absorption rate, SLM volumetric deposition …