Physics Commons^™

Charge Transport And Electron Emission Of Disordered Materials: Extensions Of The Walden-Wintle Model For Charge Injection With Electron Beams, Jr Dennison, Alec Sim, Gregory Wilson, Jodie C. Gillespie

Presentations

No abstract provided.

Pre-Breakdown Arcing And Electrostatic Discharge In Dielectrics Under High Dc Electric Field Stress, Allen Andersen, Jr Dennison

Presentations

No abstract provided.

Cathodolumiescence Studies Of The Density Of States Of Disordered Silicon Dioxide, Jr Dennison, Amberly Evans Jensen

Presentations

Electron bombardment measurements have shown that disordered SiO2 exhibits cathodoluminescence, with an overall intensity that varies with incident electron beam energy and current density, sample temperature, exposure time, and wavelength. A simple model based on the defect density of states—used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO 2 as a function of these variables. The spectral radiance exhibited four distinct bands, corresponding to four distinct energy distributions of defect states within the band gap; each showed different temperature dependence. These localized defect or “trap” …

Cathodoluminescence Events Coincident With Muon Detection, Kenneth Zia, Justin Dekany, Jr Dennison

Presentations

Samples of highly disordered insulating material have been irradiated with keV electron beams, resulting in three forms of electron induced light emission with differing duration: arcs (duration), “flares” (~100 s), and cathodoluminescence (as long as beam is on) [Dennison, 2013]. The arc and cathodoluminescence phenomena are well understood, while the flares’ origins are not. Flares were observed at intervals of ~2 per hr. This is within a factor of 2 for the expected muon cross section at an altitude of Logan, UT (1370 m) caused by high altitude cosmic rays; those high energy particles could have deposited sufficient energy throughout …

Discharge Breakdown Analyses, Sam Hansen, Jr Dennison, Allen Andersen

Presentations

Material breakdown due to Electrostatic discharge (ESD) is the primary cause of spacecraft damage due to environment interactions in space. This occurs when the space plasma fluxes charge a craft to high voltages where insulating craft materials then break down. This failure allows current to flow freely through the material, this can damage or destroy onboard electrical systems. My project focuses on the effects of these breakdowns on suspect materials commonly used for electrical insulation in space. The USU Material Physics Group has performed ESD tests on hundreds of samples to date. The ESD damage sites of these samples have …

Lifetimes Of Polymeric Dielectrics: A Dual-Defect Model, Allen Andersen, Jr Dennison

Presentations

Electrostatic discharge (ESD) can cause catastrophic failures in electronic devices. Estimating the lifetime of dielectrics under prolonged high field exposure is a major design concern for applications including spacecraft, high voltage DC power transmission, and semiconductor electronics. Dielectric strengths listed in engineering handbooks are primarily based on cursory measurements with poor repeatability and tend to overestimate ESD fields in real applications. Standard measurements subject test samples to ~500 V/s ramp rates until breakdown. We present the results of ESD studies in two prototypical polymer dielectrics using a ramp rate of ~20 V/4s until breakdown together with tests applying a static …

Modeling The Energy Dependent Cathodoluminescent Intensity Of A Carbon Composite Material, Justin Christensen, Kelby T. Peterson, Justin Dekany, Jr Dennison

Presentations

When highly disordered insulating materials are subjected to energetic electron bombardment they can emit photons. This process is termed “cathodoluminescence.” This occurs in the space plasma environment and is an important phenomenon to understand when designing any object to be put into space. Light emitted from spacecraft materials can affect optical detection, and can cause stray-light contamination in space-based observatories. The Materials Physics Group at Utah State University uses an ultra-high vacuum chamber equipped with electron guns and a cryostat to control the sample temperature to simulate the space environment and to observe its affects on sample materials. Previous studies …

Space Effects Survivability Testing, Lisa Montierth Phillipps, Jr Dennison, Kent Hartley, Robert H. Johnson, Justin Dekany, James S. Dyer

Presentations

A versatile test facility has been designed to study the effects of space environment fluxes and radiation damage on small scale materials samples, system components, and small satellites. Cost-effective long-duration testing for potentially environmental-induced modifications is increasingly more important as small satellite programs have longer mission lifetimes, expand to more harsh environments, make more diverse and sensitive measurements, minimize shielding to reduce mass, and utilize more compact and sensitive electronics. The facility simulates environmental components including the neutral gas atmosphere, the solar spectrum, electron plasma fluxes, and temperature. The UV/VIS/NIR solar spectrum is simulated using a class AAA Solar Simulator …

Guesstimation: The Art Of Getting About The Right Answer, Jr Dennison

Presentations

No abstract provided.

Cathodolumiescence Studies Of The Density Of States Of Disordered Silicon Dioxide, Jr Dennison, Amberly Evans Jensen

Presentations

Electron bombardment measurements have shown that disordered SiO2 exhibits cathodoluminescence, with an overall intensity that varies with incident electron beam energy and current density, sample temperature, exposure time, and wavelength. A simple model based on the defect density of states—used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO2 as a function of these variables. The spectral radiance exhibited four distinct bands, corresponding to four distinct energy distributions of defect states within the band gap; each showed different temperature dependence. These localized defect or “trap” states …

Investigations Of Electrical And Physical Properties Of Ceramic Materials For Spacecraft Applications, Kevin Guerch, Jr Dennison

Presentations

No abstract provided.

Dual-Defect Model Of Electrostatic Discharge In Polymeric Dielectrics, Allen Andersen, Jr Dennison

Presentations

Electrostatic discharge (ESD) is a serious concern for spacecraft, high voltage power transmission, and other applications. A parallel plate capacitor geometry under high vacuum was used to apply increasing voltages across insulating samples until ESD breakdown and to apply sub-critical fields and observe time-to-breakdown. Transient arcing was frequently observed prior to complete ESD breakdown in both cases. Results are presented for two prototypical polymeric materials, low density polyethylene (LDPE) and polyimide (PI or Kapton HN™) in terms of both statistical and physics-based models.

Many electrical aging models are described by defect creation within the material from bond stress due to …

Small Satellite Space Environments Effects Test Facility, Jr Dennison, Kent Hartley, Lisa Montierth Phillipps, Justin Dekany, James S. Dyer, Robert Johnson

Presentations

No abstract provided.

Small Satellite Space Environments Effects Test Facility, Jr Dennison, Justin Dekany, Kent Hartley, James S. Dyer, Robert H. Johnson

Presentations

No abstract provided.

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

Presentations

No abstract provided.

Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Todd Schneider, Charles W. Bowers, Robert Meloy

Presentations

Various highly insulating materials used in spacecraft construction can exhibit glow (electron-induced luminescence or cathodoluminescence) when exposed to the space plasma environment. Measurements of the absolute and relative cathodoluminescent intensity per incident electron flux of spacecraft materials are essential to predict and mitigate consequences for optical detection and for stray light contamination in space-based observatories. They also provide important information about the defect structure and electron transport properties of these materials. Previous studies have focused on how the relative spectral radiance of cathodoluminescent materials varies with changes in environmental conditions, including electron energy, current density, absorbed power density, and temperature. …

Small Satellite Space Environments Effects Test Facility, Jr Dennison, Kent Hartley, Lisa Montierth Phillipps, Robert Johnson, Justin Dekany, James Dyer

Presentations

A versatile space environments test facility has been designed and built to study the effects on small satellites and system components. Testing for potentially environmental-induced modifications of small satellites is critical to avoid possible deleterious or catastrophic effects over the duration of space missions. This is increasingly more important as small satellite programs have longer mission lifetimes, expand to more hash environments (such as polar or geosynchronous orbits), make more diverse and sensitive measurements, minimize shielding to reduce mass, and utilize more compact and sensitive electronics (often including untested off-the-shelf components). Our vacuum chamber is particularly well suited for cost-effective, …

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

Presentations

No abstract provided.

Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans, Greg Wilson, Todd Schneider, Charles W. Bowers, Robert H. Meloy

Presentations

No abstract provided.

Measurements Of Intrinsic Electron Emission Yields Of High Resistivity Ceramic Materials, Justin Dekany, Jr Dennison, Ryan Carl Hoffmann, Clint D. Thomson, Ender Savrun

Presentations

No abstract provided.

Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2, Amberly Evans Jensen, Jr Dennison

Presentations

No abstract provided.

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

Presentations

A critical component in the prediction and mitigation of spacecraft charging issues is an accurate model of the charging, transport and electron emission properties of a broad array of materials used in the construction of spacecraft. The increased sensitivity, longer-duration missions, and ventures into more demanding environments only serve to heighten this need. One important way for the spacecraft charging community to address this issue 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. …

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

Presentations

Radiation induced conductivity (RIC) occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. The increased number of charge carriers, and hence the magnitude of the enhanced conductivity, is dependent on a number of factors including temperature and the spatial and energy dependence and occupation of the material’s distribution of localized trap states within the band gap—or density of states (DOS). Expressions for RIC in terms of the filling of the DOS up to an effective Fermi level were largely developed by Rose [RCA Review, 1951], and were extended by Fowler [ …

Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model, Allen Andersen, Jr Dennison, Alec Sim, Charles Sim

Presentations

Electrostatic discharge (ESD) is the primary cause of space environment induced failures and malfunctions. As mission lifetimes and the sensitivity and complexity of instrumentation increase, so does the need for describing the influence of the electrical aging processes on ESD. This research studies the electrostatic field strength (F_ESD) of polymeric insulators as a function of applied field and the time-to-breakdown for F < F_ESD. A dynamic physics-based model for time-to-breakdown is much more valuable than an empirical static model, since it provides the ability to predict the statistical lifetime of dielectric materials subjected to prolonged stress from …

Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2,, Amberly Evans Jensen, Jr Dennison

Presentations

Electron beam measurements have shown that disordered SiO2 exhibits luminescent behavior, which varies with incident beam energy and current density, sample temperature (T), exposure time, and wavelength. A simple model based on the electronic band structure and defect density of states—used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO 2 as a function of these variables. Insulating SiO2 has a band gap of ~8.9 eV. Hence thermal excitation from the valence to conduction band is highly improbable; excitation is through collisions of the incident high …

Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model, Allen Andersen, Jr Dennison, Alec Sim, Charles Sim

Presentations

No abstract provided.

Interpretation (Or Is It Calibration?) Of Rayleigh-Scatter Lidar Signals, Vincent B. Wickwar, Leda Sox

Presentations

No abstract provided.

Lessons Learned From The Statistical Analysis Of Measurements Of The Energetic Electron Bombardment Of Epoxy ‘Glue Dots, Justin Christensen, Justin Dekany, Jr Dennison

Presentations

No abstract provided.

Stochastic Variations Of Cathodoluminescent Intensity Of Bisphenol/Amine Epoxy Exposed To Energetic Electron Bombardment, Justin Christensen, Justin Dekany, Jr Dennison

Presentations

When highly disordered insulating materials are subjected to energetic electron bombardment they can emit photons. This process is termed “cathodoluminescence.” This occurs in the space plasma environment and is an important phenomenon to understand when designing any object to be put into space. Light emitted from spacecraft materials can affect optical detection, and can cause stray-light contamination in space-based observatories. The Materials Physics Group at Utah State University uses an ultra-high vacuum chamber equipped with electron guns and a cryostat to control the sample temperature to simulate the space environment and to observe its affects on sample materials. Previous studies …

Simulation Of Uv Radiation Degradation Of Polymers On Misse-6 In The Low Earth Orbit Environment, Philip Lundgreen, Justin Dekany, Jr Dennison

Presentations

Using a high-Voltage Battery power Supply, we measured the time dependent conductivity for highly disorganized materials, and were able to model the complete conductivity curve for said materials. Previous methods were utilized and improved upon to decrease the error found in conductivity measurements through an “extremely resistive” materials. The data was subsequently analyzed using various curve fitting techniques to measure time taken for a sample to reach conductive equilibrium. The fittings were also used to predict the amount of time required for a sample to completely discharge after it had been fully charged. The objective of this study was to …