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Dynamic Secondary Electron Emission In Dielectric/Conductor Mixed Coatings, Leandro Olano, Isabel Montero, María E. Dávila, JR Dennison 2017 Instituto de Ciencia de Materiales de Madrid

Dynamic Secondary Electron Emission In Dielectric/Conductor Mixed Coatings, Leandro Olano, Isabel Montero, María E. Dávila, Jr Dennison

Presentations

An unexpected behavior of the Secondary Emission Yield (SEY) on coatings composed by a mixture of conductor and dielectric microparticles was reported and modeled in [1]. As a follow up, we measured for a fixed primary energy the dynamic evolution of the SEY in similar samples and proposed a charging-roughness coupled model to simulate the experimental results. Two different coatings were selected: 1) TMM and Al microparticles (type 1), and 2) zeolites and gold nanoparticles (type 2). Pulsed and continuous tests were used to obtain the SEY as a function of the primary energy.

In both types of samples extremely ...


A New Physical Model For Dc Partial Discharge In Polymeric Insulators, Allen Andersen, JR Dennison 2017 Utah State University

A New Physical Model For Dc Partial Discharge In Polymeric Insulators, Allen Andersen, Jr Dennison

Presentations

The physics of DC partial discharge (DCPD) continues to pose a challenge to researchers. We present a new physically-motivated model of DCPD in amorphous polymers based on our dual-defect model of dielectric breakdown. The dual-defect model is an extension of standard static mean field theories, such as the Crine model, that describe avalanche breakdown of charge carriers trapped on uniformly distributed defect sites. It assumes the presence of both high-energy chemical defects and low-energy thermally-recoverable physical defects. We present our measurements of breakdown and DCPD for several common polymeric materials in the context of this model. Improved understanding of DCPD ...


Model For Charge Injection With Electron Beams Into Highly Disordered Insulating Materials, JR Dennison 2017 Utah State Univesity

Model For Charge Injection With Electron Beams Into Highly Disordered Insulating Materials, Jr Dennison

Presentations

The Walden-Wintle model for charge injection and transport through highly disordered insulating materials has been extended to include charge injection with a charged particle beam. The original model is applicable to charge injection into a dielectric material from a pair of electrodes in a parallel-plate geometry. It provides a versatile approach to predict the time-dependent current at a rear grounded electrode and the incident surface voltage, as the injection current density evolves over time with the development of a space charge barrier near the injection electrode. The Walden-Wintle model has been applied to many standard cases including Fowler-Nordheim injection, Schottky ...


Physical Properties Of Single Crystalline R Mg 2 Cu 9 ( R = Y , Ce − Nd , Gd − Dy , Yb ) And The Search For In-Plane Magnetic Anisotropy In Hexagonal Systems, Tai Kong, William R. Meier, Qisheng Lin, Scott M. Saunders, S. L. Bud’ko, Rebecca Flint, Paul C. Canfield 2017 Iowa State University

Physical Properties Of Single Crystalline R Mg 2 Cu 9 ( R = Y , Ce − Nd , Gd − Dy , Yb ) And The Search For In-Plane Magnetic Anisotropy In Hexagonal Systems, Tai Kong, William R. Meier, Qisheng Lin, Scott M. Saunders, S. L. Bud’Ko, Rebecca Flint, Paul C. Canfield

Qisheng Lin

Single crystals ofRMg2Cu9 (R = Y, Ce-Nd, Gd-Dy, Yb) were grown using a high-temperature solution growth technique and were characterized by measurements of room-temperature x-ray diffraction, temperature-dependent specific heat, and temperature- and field-dependent resistivity and anisotropic magnetization. YMg2Cu9 is a nonlocal- moment-bearing metal with an electronic specific heat coefficient, γ ∼ 15 mJ/mol K2. Yb is divalent and basically non-moment-bearing in YbMg2Cu9. Ce is trivalent in CeMg2Cu9 with two magnetic transitions being observed at 2.1 K and 1.5 K. PrMg2Cu9 does not exhibit any magnetic phase transition down to 0.5 K. The other members being studied (R = Nd ...


The Effects Of Tilted Magnetic Fields On Quantum Transport In 2d Electron Systems, William A. Mayer 2017 The Graduate Center, City University of New York

The Effects Of Tilted Magnetic Fields On Quantum Transport In 2d Electron Systems, William A. Mayer

All Graduate Works by Year: Dissertations, Theses, and Capstone Projects

There exists a myriad of quantum transport phenomena in highly mobile 2D electrons placed in a perpendicular magnetic field. We study the effects of tilted magnetic field on these transport properties to understand how the energy spectrum evolves. We observe significant changes of the electron transport in quantum wells of varying widths with high electron densities at high filling factors. In narrow quantum wells the spin splitting of Landau levels due to Zeeman effect is found to be the dominant mechanism reducing Quantum Positive Magnetoresistance. In wider quantum wells with two populated subbands Magnetointersubband oscillations appear to exhibit effects from ...


Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Joeng-Young Ji, William A. Booth 2017 Utah State University

Interactions Between Uniformly Magnetized Spheres, Boyd F. Edwards, D. Mark Riffe, Joeng-Young Ji, William A. Booth

D. Mark Riffe

We use simple symmetry arguments suitable for undergraduate students to demonstrate that the magnetic energy, forces, and torques between two uniformly magnetized spheres are identical to those between two point magnetic dipoles. These arguments exploit the equivalence of the field outside of a uniformly magnetized sphere with that of a point magnetic dipole, and pertain to spheres of arbitrary sizes, positions, and magnetizations. The point dipole/sphere equivalence for magnetic interactions may be useful in teaching and research, where dipolar approximations for uniformly magnetized spheres can now be considered to be exact. The work was originally motivated by interest in ...


Density Of State Models And Temperature Dependence Of Radiation Induced Conductivity, Jodie Corbridge Gillespie, JR Dennison, Alec M. Sim 2017 Utah State University

Density Of State Models And Temperature Dependence Of Radiation Induced Conductivity, Jodie Corbridge Gillespie, Jr Dennison, Alec M. Sim

Journal Articles

Expressions are developed for radiation induce conductivity (RIC) over an extended temperature range, based on density of states models for highly disordered insulating materials. A general discussion of the DOS of can be given using two simple types of DOS distributions of defect states within the bandgap for disordered materials are considered, one that monotonically decreases within the bandgap and one with a distribution peak within the band gap. Three monotonically decreasing models (exponential, power law, and linear), and two peaked models (Gaussian and delta function) are considered, plus limiting cases with a uniform DOS for each type. Variations using ...


Temporal And Spatial Correlations In Electron-Induced Arcs Of Adjacent Dielectric Islands, Justin Christensen, JR Dennison, Justin Dekany 2017 Utah State University

Temporal And Spatial Correlations In Electron-Induced Arcs Of Adjacent Dielectric Islands, Justin Christensen, Jr Dennison, Justin Dekany

Journal Articles

This study investigates very short duration (<1ms) flashes caused by rapid discharge arcs from isolated charged insulating epoxy “glue dots” to an underlying grounded substrate while under electron bombardment. The possibility that a given arc might stimulate arcs in adjacent “glue dots” was investigated through coincidence correlation analysis, as was the dependence of such correlations with “glue dot” separation. Most arcs were found to be random localized events, which occurred only when built up charge produced an electric field large enough for electrostatic breakdown to occur. However, for 40 keV incident beams, some correlation was observed. It is hypothesised that at higher energies more samples are charged close to the breakdown field at any given time and that a discharge in one “glue dot” might cause a sudden electric field spike in neighbouring “glue dots” which could trigger premature arcing. Such stimulated arc rates might reasonably be expected to scale with electric field intensity. A power law fit to the arc data found a power of -1.06±0.09, consistent with a field falling off inversely with separation distance for charges spreading out across a 2D conducting surface.


Pea System Modeling And Signal Processing For Measurement Of Volume Charge Distributions In Thin Dielectric Films, Lee H. Pearson, JR Dennison, Erick W. Griffiths, Anthony C. Pearson 2017 Box Elder Innovations

Pea System Modeling And Signal Processing For Measurement Of Volume Charge Distributions In Thin Dielectric Films, Lee H. Pearson, Jr Dennison, Erick W. Griffiths, Anthony C. Pearson

Journal Articles

This paper discusses our effort to develop advanced pulsed electroacoustic (PEA) measurement system capabilities that incorporate (1) improved signal processing tools for increased signal/noise ratios; and (2) integrated PEA modeling tools. In addition, we emphasize state-of-the-art system electronic components, integrated environmental controls, and sensor improvements required to achieve high spatial resolution while maintaining reasonable temporal resolution for both ambient and in vacuo measurements of thin dielectrics charged using electron beam injection, which is most applicable for spacecraft charging tests. PEA measurement systems provide an important tool to investigate the spatial extent and dynamic evolution of embedded charge distributions in ...


Electron-Energy-Loss Spectroscopy Of Yba2cu3-Xfexo7-Y Superconductors, Prem P. Vaishnava, C. A. Taylor II, C. L. Foiles 2016 GMI Engineering & Management Institute

Electron-Energy-Loss Spectroscopy Of Yba2cu3-Xfexo7-Y Superconductors, Prem P. Vaishnava, C. A. Taylor Ii, C. L. Foiles

Prem Vaishnava

YBa2Cu3 „Fe„07 ~ (x =0.0, 0.05, 0.1) compounds have been studied using energy-dispersive xray (EDX) and electron-energy-loss spectroscopy (EELS). X-ray diffraction data indicated the formation of structurally known superconducting compounds. Transition temperatures, as measured by a Faraday balance, showed a decrease as the iron concentration was increased. Using the spot mode in an analytical electron microscope, the EDX and EELS data were obtained for identifiable, well-defined small regions of the superconducting particles. EDX spectra have been used to analyze different components and phases present in the samples. Detailed EELS data for the 0 1s excitation have been ...


Superconductivity Versus Structural Phase Transition In The Closely Related Bi2rh3.5s2 And Bi2rh3s2, Udhara S. Kaluarachchi, Weiwei Xie, Qisheng Lin, Valentin Taufour, Sergey L. Bud'ko, Gordon J. Miller, Paul C. Canfield 2016 Iowa State University

Superconductivity Versus Structural Phase Transition In The Closely Related Bi2rh3.5s2 And Bi2rh3s2, Udhara S. Kaluarachchi, Weiwei Xie, Qisheng Lin, Valentin Taufour, Sergey L. Bud'ko, Gordon J. Miller, Paul C. Canfield

Qisheng Lin

Single crystals of Bi2Rh3S2 and Bi2Rh3.5S2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case ofBi2Rh3S2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi2Rh3S2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi2Rh3.5S2; however, bulk superconductivity with a critical temperature, Tc≈1.7 K, was observed. The Sommerfeld coefficient γ and the ...


Nanoscale Thermal And Electronic Properties Of Thin Films Of Graphene And Organic Polyradicals, Sabastine Chukwuemeka Ezugwu 2016 The University of Western Ontario

Nanoscale Thermal And Electronic Properties Of Thin Films Of Graphene And Organic Polyradicals, Sabastine Chukwuemeka Ezugwu

Electronic Thesis and Dissertation Repository

Ultrathin film materials have attracted significant attention in light of their potential applications in very large scale integrated electronics and data storage. For instance, the amount of data that can be addressed and stored in a memory device scales inversely with the thinness of the active layer of these components. In our thesis, we have developed a suite of scanning-probe and nano-optical techniques focused on understanding the electronic surface properties and the thermal conductivity of ultrathin materials. We discuss a few specific examples in which we applied these techniques towards improved performance of thin films of graphene and organic polyradicals ...


Voltage Ramp-Rate Dependence Of Dc Breakdown In Polymeric Insulators: Physical Models Versus Data, Allen Andersen, Krysta Moser, JR Dennison 2016 Utah State University

Voltage Ramp-Rate Dependence Of Dc Breakdown In Polymeric Insulators: Physical Models Versus Data, Allen Andersen, Krysta Moser, Jr Dennison

Allen Andersen

The standard handbook values for dielectric breakdown strength of necessity come from accelerated test methods. In some cases, the breakdown voltage may vary significantly with voltage ramp rates; therefore, a theoretical model for the ramp-rate dependence of breakdown is needed to extrapolate from realistic tests to long-duration material service lifetimes. Series of step-up to breakdown tests were performed for ramp rates from 0.5 to 500 V/s for biaxially-oriented polypropylene (BOPP), low density polyethylene (LDPE), and polyimide (PI) films. The data were fit with standard empirical methods, as well as two physics-based defect-driven models. Empirical models can be fit ...


Linear Feedback Stabilization For A Continuously Monitored Qubit, Taylor Lee Patti, A. Chantasri, Justin Dressel, A. N. Jordan 2016 Chapman University

Linear Feedback Stabilization For A Continuously Monitored Qubit, Taylor Lee Patti, A. Chantasri, Justin Dressel, A. N. Jordan

Student Research Day Abstracts and Posters

In quantum mechanics, standard or strong measurement approaches generally result in the collapse of an ensemble of wavefunctions into a stochastic mixture of eigenstates. On the other hand, continuous or weak measurements have the propensity to dynamically control the evolution of quantum states over time, guiding the trajectory of the state into non-trivial superpositions and maintaining state purity. This kind of measurement-induced state steering is of great theoretical and experimental interest for the harnessing of quantum bits or "qubits", which are the fundamental unit of the emerging quantum computer. We explore continuous measurement-based quantum state stabilization through linear feedback control ...


Dependence Of Electrostatic Field Strength On Voltage Ramp Rate For Spacecraft Materials, Krysta Moser, Allen Andersen, JR Dennison 2016 Utah State University

Dependence Of Electrostatic Field Strength On Voltage Ramp Rate For Spacecraft Materials, Krysta Moser, Allen Andersen, Jr Dennison

Allen Andersen

This work investigated the dependence of electrostatic field strength for spacecraft materials on voltage ramp rate, by applying an increasing electrostatic field until electrostatic breakdown occurred. Tests on the polymeric material Kapton ETM found that at ramp rates two or three orders of magnitude lower than the maximum recommended rate, FESD was lower than at rapid rates by a factor or two or more this suggests that tabulated values of FESD which have been used by the spacecraft charging community can substantially overestimate FESD in common slowly evolving spacecraft situations. Similar measurements on other polymeric materials have been performed to ...


Effects Of Voltage Ramp Rates On Electrostatic Field Strength In Highly Disordered Insulating Materials, Krysta Moser, Allen Andersen, JR Dennison 2016 Utah State University

Effects Of Voltage Ramp Rates On Electrostatic Field Strength In Highly Disordered Insulating Materials, Krysta Moser, Allen Andersen, Jr Dennison

Allen Andersen

At high enough electrostatic fields or after long exposure times, insulators can break down, causing large current flow through the material: this breakdown is called electrostatic discharge (ESD). ESD is a permanent, catastrophic failure of a dielectric material: what was an insulator is now essentially a conductor. Previous tests done by the USU Materials Physics Group (MPG) using our ESD custom vacuum chamber have found that, for the polymeric materials biaxially oriented polypropylene (BOPP), polyimide (PI), and low density polyethylene (LDPE), the electrostatic field strength at breakdown depends on the ramp rate of voltage applied across some materials, but possibly ...


Plasma Deflection Test Setup For E-Sail Propulsion Concept, Allen Andersen, Jason Vaughn, Todd Schneider, Ken Wright 2016 Utah State University

Plasma Deflection Test Setup For E-Sail Propulsion Concept, Allen Andersen, Jason Vaughn, Todd Schneider, Ken Wright

Allen Andersen

The Electronic Sail or E-Sail is a novel propulsion concept based on momentum exchange between fast solar wind protons and the plasma sheath of long positively charged conductors comprising the E-Sail. The effective sail area increases with decreasing plasma density allowing an E-Sail craft to continue to accelerate at predicted ranges well beyond the capabilities of existing electronic or chemical propulsion spacecraft. While negatively charged conductors in plasmas have been extensively studied and flown, the interaction between plasma and a positively charged conductor is not well studied. We present a plasma deflection test method using a differential ion flux probe ...


Voltage Ramp-Rate Dependence Of Dc Breakdown In Polymeric Insulators: Physical Models Versus Data, Allen Andersen, Krysta Moser, JR Dennison 2016 Utah State University

Voltage Ramp-Rate Dependence Of Dc Breakdown In Polymeric Insulators: Physical Models Versus Data, Allen Andersen, Krysta Moser, Jr Dennison

Allen Andersen

Purpose/Aim

The standard handbook values for dielectric breakdown strength of necessity come from accelerated test methods. In some applications the breakdown voltage may vary significantly with voltage ramp rates; therefore, a theoretical model for the ramp-rate dependence of breakdown is needed to extrapolate from realistic tests to long-duration material service lifetimes.

Experimental/Modeling methods

Series of step-up to breakdown tests were performed for ramp rates from 0.5 to 500 V/s for biaxially-oriented polypropylene (BOPP), low density polyethylene (LDPE), and polyimide (PI) films. The data were fit with standard empirical methods, as well as two physics-based defect-driven models ...


Synergistic Models Of Electron Emission And Transport Measurements Of Disordered Sio2, JR Dennison, Jodie Corbridge Gillespie, Allen Andersen, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Alec Sim, Ryan C. Hoffmann 2016 Utah State Univesity

Synergistic Models Of Electron Emission And Transport Measurements Of Disordered Sio2, Jr Dennison, Jodie Corbridge Gillespie, Allen Andersen, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Alec Sim, Ryan C. Hoffmann

Allen Andersen

An important way for the spacecraft charging community to address the expanding necessity for extensive characterization of electron emission and transport properties of materials is to expand the role of more fundamental materials physics. This includes the development of unifying theoretical models of the charge transport equations based on the creation, distribution, and occupancy of defect densities of states. Models that emphasize the synergistic relation between fitting parameters for diverse measurements can also lead to a better understanding of materials and facilitate solutions to spacecraft charging issues. As an example of this approach, we present results of many different measurements ...


Perspectives On The Distributions Of Esd Breakdowns For Spacecraft Charging Applications, Allen Andersen, Krysta Moser, JR Dennison 2016 Utah State University

Perspectives On The Distributions Of Esd Breakdowns For Spacecraft Charging Applications, Allen Andersen, Krysta Moser, Jr Dennison

Allen Andersen

Electrostatic discharge (ESD) continues to pose significant risks to space missions despite decades of intense study. We emphasize here the advantages to spacecraft designers and modelers from considering the stochastic distributions of breakdown and how it can be affected by factors including spacecraft environment conditions, design geometries, material temperature, material purity, charging history, and appropriate timescales. Spacecraft charging models and spacecraft designs typically rely on tabulated values or ranges of breakdown strength, often based on cursory measurements with little or no experimental detail. Depending on the timescales and history of environmental and orbital changes or durations of specific missions, it ...


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