Condensed Matter Physics Commons^™

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

Conference Proceedings

Electron beam measurements have been made that show disordered SiO 2 exhibits luminescent behavior, and that it varies with incident beam energy and current density, sample temperature and wavelength. A simple model based on the electronic band structure and defect density of states—initially 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 SiO 2 has a band gap of ~8.9 eV. Hence thermal excitation from the valence to conduction band is highly improbable; excitation is through collisions …

Improved Measurements In Conductivity For Highly Disorganized Resistive Materials, Phil Lundgreen

Senior Theses and Projects

Determining the electrical properties of highly insulating materials can be a challenging task. These materials are designed to greatly resist the flow of electrical current. This makes them useful for various applications including terrestrial transmission lines, spacecraft charging, and capacitor-driven charge storage devices. Every year over 370 billion kWhr are lost during transportation along power lines in the US. That is roughly $36B which is thrown away each year due to inefficiency in our power transmission network (1). Due to the fact that satellites are isolated from ground, charging caused by the plasma environment found at typical orbital radii (2) …

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.

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 …

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 …

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

Presentations

Electrostatic discharge (ESD) and the associated material breakdown is the primary cause for spacecraft damage due to space environment interactions. This phenomenon occurs when the space plasma fluxes charge a craft to high voltages where insulating materials then break down and conduct current. This can damage or destroy onboard electrical systems. This project deals with how suspect materials break down under high voltage exposure. The USU Material Physics Group has acquired hundreds of samples that underwent ESD. The ESD damage sites of these samples have been analyzed for parameters including breakdown size, shape, coloring, and location and material characteristics such …

Faraday Cup Designs For High Efficiency Determination Of Energy- And Angular-Resolved Charged Particle Fluxes, Kent Hartley, Jr Dennison

Senior Theses and Projects

In order to build a spacecraft, we must understand how the construction materials will behave in the space environment (i.e. when subjected to the solar wind). The USU Materials Physics Group performs electron emission tests on spacecraft materials in an Ultra-high vacuum (UHV) test chamber (Fig.1). The chamber utilizes Faraday cups (Fig.2) in order to quantify electron flux at a location within the chamber. This measurement is important in characterizing beam profiles of electron guns used in UHV experiments. Perhaps more importantly, the Faraday cups are used to detect secondary electrons (SE) and back-scattered electrons (BSE) emitted from the surface …

Marshall Space Flight Center Arc/Flare Test Analysis, Charles Bowers, Bob Meloy, Malcolm Niedner, Jim Heaney, Rudy Ivancic, Dennis Skelton, Jr Dennison, Justin Dekany, Amberly Evans Jensen, Gregory Wilson, Todd Schneider

Presentations

No abstract provided.

Improved Conductivity Measurements Of Highly Disordered Insulating Materials, Phil Lundgreen, Justin Dekany, Jr Dennison

Presentations

By developing a low-noise, high-voltage battery power supply, system noise has been reduced, increasing accuracy of conductivity measurements of highly disordered insulating materials. The method involves a simple parallel plate capacitor setup with the sample sandwiched between electrodes, a voltage potential applied to one electrode, and a measurement device applied to the back electrode measuring current. Previous methods involved use of a commercial power supply with a claimed low noise and high linearity, but with a low AC output ripple. At high voltages (1000 V), however, the noise became apparent in the readings and an unacceptable uncertainty was introduced in …

Cathodoluminescence Measurements Of Several Bisphenol/Amine Epoxy Samples, Justin Christensen

Senior Theses and Projects

No abstract provided.

Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen

Theses and Dissertations

Spacecraft charging is the accumulation of an electrical charge on orbiting spacecraft induced by the space plasma environment and has harmful effects on the electrical functionality of a spacecraft. This is studied extensively, particularly in the Materials Physics Group (MPG) at Utah State University (USU). During charging studies performed by the MPG, another potentially problematic effect of the space plasma environment on spacecraft was observed: light emanating from the sample undergoing electron beam bombardment. Space-based observatories are one type of spacecraft on which this luminescence may occur. If the luminescence from the material caused by the space plasma is within …

Feasibility Of Detecting Spacecraft Charging And Arcing By Remote Sensing, Dale C. Ferguson, Jeremy Murray Krezan, David A. Barton, Jr Dennison, Stephen Gregory

Journal Articles

More than 50 years after the dawn of the space age, most spacecraft still do not have sensors onboard capable of detecting whether they are at potentials likely to put them at risk of severe charging and the concomitant arcing, or, indeed, even capable of detecting when or if they undergo arcing. As a result, anomaly resolution has often been hit or miss, and false diagnoses are probably common. In this paper, a few remote sensing techniques that could be applied for remotely detecting spacecraft charging and/or arcing, and their feasibility, are examined: surface glows from high-energy electron impact, x-rays …

Faraday Cup Designs For High Efficiency Determination Of Energy- And Angular-Resolved Charged Particle Fluxes, Kent D. Hartley

Senior Theses and Projects

Faraday cups provide a simple and efficient apparatus to measure the absolute magnitude of charge particle fluxes, and with the addition of a retarding field analyzer and defining apertures the capability to determine the energy and angular distributions of the fluxes. Through careful design of the electron optics, a Faraday cup can be tailored to meet specific requirements for detector size, minimum detectable flux, collection efficiency, absolute accuracy, energy discrimination, and angular resolution. This project explores optimal design concepts through electric field and charged particle trajectory simulations, theoretical analysis, and evaluation of experimental prototypes to develop compact, high efficiency Faraday …

Charging Effects Of Multilayered Dielectric Spacecraft Materials: Surface Voltage, Discharge And Arcing, Gregory Wilson, Amberly Evans Jensen, Justin Dekany, Jr Dennison

Conference Proceedings

Charging of thin-film, multilayer dielectric materials subject to electron bombardment was found to evolve with time. The charging behavior was also highly dependent on the incident energy of the monoenergetic electron beams; this is driven by energy dependant processes including the electron penetration depth, electron emission, and material conductivity. The electron penetration depth is the average range to which incident electrons at a given incident energy penetrate into the material, thus defining the mean depth of an embedded charge layer. The secondary electron yield is the ratio of electrons emitted from the surface to the number of incident electrons; this …

Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Jr Dennison

Conference Proceedings

In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …

The Effects Of Surface Roughness On Diffuse Optical Reflection And Photoyields On Spacecraft Materials, Amberly Evans Jensen

Senior Theses and Projects

The goal of this project was to measure the change in the absorbance of spacecraft materials due to changes in the surface of the material. The absorbance was obtained by measuring reflectance and transmittance. We found that modifying the surface of a material did affect the material’s specular reflectance. However, the change may not have been entirely due to an increase in absorbance, but may also imply an increase in the diffuse reflection. To understand the affect on absorbance, diffuse reflectance and transmission will need to be measured. This will lead to a prediction of how surface modification affects the …

Evaluation Of The Temperature Dependence Of Endurance Models Of Electrostatic Breakdown, Charlie Sim, Jr Dennison

Senior Theses and Projects

The goal of this research was to investigate temperature and time dependent models for the electrostatic breakdown of polymeric spacecraft insulators. Temperature dependent breakdown was found by inducing an electrostatic breakdown in the prototypical polymer Low Density Polyethylene (LDPE) at various temperatures. Time dependent breakdown was found by applying a static voltage to LDPE and measuring the time to electrostatic breakdown. No significant temperature dependence of the electrostatic breakdown of LDPE was observed in a temperature range of 150 K to 300 K. The time dependent results show that the time to electrostatic breakdown is modeled by a negative logarithmic …

Surface Geometry And Heat Flux Effect On Thin Wire Nucleate Pool Boiling Of Subcooled Water In Microgravity, Troy Munro, Andrew Fassman, Heng Ban, Jr Dennision

Conference Proceedings

In the summer of 2010, undergraduates from the USU Get Away Special team flew a nucleate pool boiling experiment on NASA’s Weightless Wonder to study nucleate boiling heat transfer in microgravity. The motivation of this research was to understand the effects of surface geometry and heat flux applied to a thin wire heater for the design and development of efficient thermal management systems for space applications. The specific objectives were to observe and characterize behaviors of boiling onset, steady state heat transfer, and bubble dynamics with respect to nucleate boiling of subcooled water.. Using three thin platinum wire geometries and …

Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, Jr Dennison, John Prebola, Amberly Evans Jensen, Joshua L. Hodges

Conference Proceedings

The effects of prolonged exposure to the LEO space environment and charge-enhanced contamination on optical, thermal, and electron emission and transport properties of common spacecraft materials has been investigated by comparing pre- and post-flight characterization measurements. The State of Utah Space Environment & Contamination Study (SUSpECS) deployed in March 2008 on board the Materials International Space Station Experiment (MISSE-6) payload, was exposed for ~18 months on the exterior of the International Space Station (ISS), before retrieval in September 2009. A total of 165 samples were …

Hopping Conductivity And Charge Transport In Low Density Polyethylene, Jerilyn Brunson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The properties and behaviors of charge transport mechanisms in highly insulating polymers are investigated by measuring conduction currents through thin film samples of low density polyethylene (LDPE). Measurements were obtained using a constant voltage method with copper electrodes inside a chamber adapted for measurements under vacuum and over a wide range of temperatures and applied fields. Field-dependent behaviors, including Poole-Frenkel conduction, space charge limited current (SCLC), and Schottky charge injection, were investigated at constant temperature. These field-dependent mechanisms were found to predict incorrect values of the dielectric constant and the field dependence of conductivity in LDPE was not found to …

Electron-Induced Electron Yields Of Uncharged Insulating Materials, Ryan Carl Hoffmann

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Presented here are electron-induced electron yield measurements from high-resistivity, high-yield materials to support a model for the yield of uncharged insulators. These measurements are made using a low-fluence, pulsed electron beam and charge neutralization to minimize charge accumulation. They show charging induced changes in the total yield, as much as 75%, even for incident electron fluences of <3 fC/mm², when compared to an uncharged yield. The evolution of the yield as charge accumulates in the material is described in terms of electron recapture, based on the extended Chung and Everhart model of the electron emission spectrum and the dual dynamic …

Evaluation Of The Temperature And Time Dependence Of Electrostatic Breakdown, Charlie Sim

Senior Theses and Projects

The goal of this research was to investigate temperature and time dependent models for the electrostatic breakdown of polymeric spacecraft insulators. Temperature dependent breakdown was found by inducing an electrostatic breakdown in the prototypical polymer Low Density Polyethylene (LDPE) at various temperatures. Time dependent breakdown was found by applying a static voltage to LDPE and measuring the time to electrostatic breakdown. No significant temperature dependence of the electrostatic breakdown of LDPE was observed in a temperature range of 150 K to 300 K. The time dependent results show that the time to electrostatic breakdown is modeled by a negative logarithmic …

Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, Jr Dennison, John Prebola, Amberly Evans, Danielle Fullmer, Joshua L. Hodges, Dustin H. Crider, Daniel S. Crews

Conference Proceedings

The effects of prolonged exposure to the LEO space environment and charge-enhanced contamination on optical, thermal, and electron emission and transport properties of common spacecraft materials have been investigated by comparing pre- and post-flight characterization measurements. The State of Utah Space Environment and Contamination Study (SUSpECS) deployed in March 2008 on board the Materials International Space Station Experiment (MISSE-6) payload, was exposed for ~18 months on the exterior of the International Space Station (ISS), and was retrieved in September 2009. A total of 165 samples were mounted on three separate SUSpECS panels on the ram and wake sides on the …

Electrostatic Discharge In Spacecraft Materials, Jennifer Roth, Jr Dennison, Ryan C. Hoffman, David Peak

Senior Theses and Projects

Understanding the characteristics of electron beam bombardment that induce electrostatic discharge (ESD) of insulating materials is crucial to constructing an electrically stable spacecraft. A measurement system has been designed to determine the beam energy and charge flux densities at which typical spacecraft materials intended for the James Webb Space Telescope (JWST) undergo ESD. Because discharge events occur over time intervals ranging from nanoseconds to minutes, multiple detection methods were employed as charge was accumulated on a sample surface; these methods included monitoring of sample current and optical emissions from the sample surface. Each sample was also examined with optical microscopy …

Temperature Dependence Of Radiation Induced Conductivity In Insulators, Jr Dennison, Jodie Corbridge Gillespie, Joshua Hodges, Ryan C. Hoffman, J Abott, Steven Hart, Alan W. Hunt

Journal Articles

We report on measurements of Radiation Induced Conductivity (RIC) of thin film Low Density Polyethylene (LDPE) samples. RIC occurs when incident ionizing radiation deposits energy in a material and excites electrons into conduction states. RIC is calculated as the difference in sample conductivity under an incident flux and “dark current” conductivity under no incident radiation.

The primary focus of this study is the temperature dependence of the steady state RIC over a wide range of absorbed dose rates, from cryogenic temperatures to well above room temperature. The measured RIC values are compared to theoretical predictions of dose rate and temperature …

Engineering Tool For Temperature, Electric Field And Dose Rate Dependence Of High Resistivity Spacecraft Materials, Jr Dennison, Steven Hart, Jodie Corbridge Gillespie, Justin Dekany, Charles Sim, Dan Arnfield

Conference Proceedings

An engineering tool has been developed to predict the equilibrium resistivity of common spacecraft insulating materials as a function of electric field (Ε), temperature (T), and adsorbed dose rate (Ď) based on parameterized, analytic functions used to model an extensive data set taken by the Utah State University Materials Physics Group. The ranges of E, T and Ď measured in the experiments were designed to cover as much of the ranges typically encountered in space environments as possible: (i) the typical electric field range was from 10⁴ V-m^-1 to 10⁷ V-m^-1 or from <0.1% up to between 30% to 90%of the electrostatic breakdown field strength; (ii) temperature was measured and modeled over a typical range of 150 K to 330 K (within limits noted below); and the adsorbed dose rate was measured and modeled over a range of 10^-5 Gray …

Measurement Of Charging And Discharging Of High Resistivity Materials Spacecraft Materials By Electron Beams, Ryan Hoffmann, Joshua L. Hodges, Jesse Hayes, Jr Dennison

Conference Proceedings

New instrumentation has been developed for in situ measurements of the electron beam- induced surface voltage of high resistivity spacecraft materials in an existing ultra-high vacuum electron emission analysis chamber. Design details, calibration and characterization measurements of the system are presented, showing sensitivity to a range of surface voltages from12000 V, with resolution surface, using a paddle attached to a vacuum compatible stepper motor mounted within a hemispherical grid retarding field analyzer. These electrodes formed one end of a floating charge transfer probe that enabled measurements to be made by a standard electrostatic field probe external to the vacuum chamber. …

Intergranular Phases In Cyclically Annealed Yba2cu3o7-X And Their Implications For Critical Current Densities, Andrew Peter Clarke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We report changes in the intergranular material and grain morphology of YBa₂Cu₃O_7-x during cyclic anneals between 780 and 980 ºC in oxygen at atmospheric pressure. Two endothermic reactions were detected: (a) the eutectic reaction of YBa₂Cu₃O_7-x with CuO and BaCuO₂ at 900 ºC (enthalpy ∆H_a) and (b) the peritectic reaction of YBa₂Cu₃O_7-x with CuO at 950 ºC (∆H_b). During the first anneal, only reaction (b) is detected, and although it should only occur if there is an excess of CuO, …

Deep Dielectric Charging Of Spacecraft Polymers By Energetic Protons, Nelson W. Green, Jr Dennison

Journal Articles

The majority of research in the field of spacecraft charging concentrates on electron charging effects with little discussion of charging by protons. For spacecraft orbiting in the traditional LEO and GEO environments, this emphasis on electrons is appropriate since energetic electrons are the dominant species. However, for spacecraft in orbits within the inner radiation belts, or for interplanetary and lunar space probes, proton charging effects may also be of concern. To examine bulk spacecraft charging effects in these environments, several typical highly insulating spacecraft polymers were exposed to energetic protons with energies from 1 to 10 MeV to simulate protons …

Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffmann, Jr Dennison, Clint D. Thomson, Jennifer Albretson

Journal Articles

Electron-induced electron yields of high-resistivity, high-yield materials - ceramic polycrystalline aluminum oxide and the polymer polyimide (Kapton HN), - were made by using a low-fluence, pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of <3 fC/mm². The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron re-capture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain anomalies measured in highly insulating, …