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Full-Text Articles in Physics

Measuring And Modeling The Conductivity Of Highly Insulating Materials, David King Aug 2017

Measuring And Modeling The Conductivity Of Highly Insulating Materials, David King

Senior Theses and Projects

Satellites and other spacecraft must be able to withstand hazardous conditions in order to be viable in their expected operating environments. One specific hazard that occurs due to incident radiation is spacecraft charging. Insulating materials, frequently used in spacecraft and other electrical equipment, while very good at preventing charge flow, also store charge very well. This can create problems; specifically, “if the charge decay time exceeds the orbital period, not all charge will be dissipated before orbital conditions act again to further charge the satellite. As the insulator accumulates charge, the electric field will rise until the insulator breaks down ...


Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison Jan 2015

Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison

Journal Articles

While the effects on spacecraft charging from varying environmental conditions and from the selection of different construction materials have been studied extensively, modification of materials properties by exposure to the space plasma environment can also have profound effects on spacecraft charging. Given the increasingly demanding nature of space missions, there is a clear need to extend our understanding of the dynamic nature of material properties that affect spacecraft charging and to expand our knowledgebase of materials’ responses to specific environmental conditions so that we can more reliably predict the long term response of spacecraft to their environment. This paper focuses ...


Time Dependent Conductivity Of Low Density Polyethylene, Phillip Lundgreen, Justin Dekany, Jr Dennison Oct 2013

Time Dependent Conductivity Of Low Density Polyethylene, Phillip Lundgreen, Justin Dekany, Jr Dennison

Posters

The time independent conductivity of Low Density Polyethylene (LDPE) is useful in determining rates of conductivity based on intrinsic properties of a material. A simple, yet elegant, parallel plate capacitor setup allowed for data collection which extended beyond 97 hours. Through precise measurements the different stages of charge distribution were determined to the level of 3 10-16 A. Through the use of data analysis programs, the dielectric constant and dispersion constant were both determined for LDPE and then compared with a simple, macroscopic, first-principles model to determine the quality of the fit.


Nanodielectric Properties Of High Conductivity Carbon-Loaded Polyimide Under Electron-Beam Irradiation, Amberly Evans, J. R. Dennison, Gregory Wilson, Justin Dekany Jun 2013

Nanodielectric Properties Of High Conductivity Carbon-Loaded Polyimide Under Electron-Beam Irradiation, Amberly Evans, J. R. Dennison, Gregory Wilson, Justin Dekany

Posters

Electron irradiation experiments were conducted to investigate the electron transport, charging, discharging, cathodoluminescence and emission properties of high-conductivity carbon-loaded polyimide (Black KaptonTM). We discuss how these results are related to the nanoscale structure of the composite material. Measurements were conducted in an ultrahigh vacuum electron emission test chamber from <40 K to 290 K, using a monoenergetic beam with energies ranging from 3 keV to 25 keV and flux densities from 0.1 nA/cm2 to 100 nA/cm2 to deposit electrons in the material surface layer. Various experiments measured transport and displacement currents to a rear grounded electrode, absolute electron emission yields, absolute electron-induced photon emission yields and photon emission spectra (~250 nm to 1700 nm), and arcing rates and location. Numerous ...


Measurement Of The Temperature Dependence Of Radiation Induced Conductivity In Polymeric Dielectrics, Jodie Corbridge Gillespie May 2013

Measurement Of The Temperature Dependence Of Radiation Induced Conductivity In Polymeric Dielectrics, Jodie Corbridge Gillespie

All Graduate Theses and Dissertations

This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HNTM and Kapton ETM), polytetraflouroethylene (PTFE or TeflonTM), ethylene-tetraflouroethylene (ETFE or TefzelTM), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at ...


Electron Energy Dependent Charging Effects Of Multilayered Dielectric Material, Gregory Wilson, Jr Dennison, Amberly Evans Jensen, Justin Dekany Jan 2013

Electron Energy Dependent Charging Effects Of Multilayered Dielectric Material, Gregory Wilson, Jr Dennison, Amberly Evans Jensen, Justin Dekany

Graduate Student Publications

Measurements of the charge distribution in electron-bombarded, thin-film, and multilayer dielectric samples showed that charging of multilayered materials evolves with time and is highly dependent on incident energy; this is driven by electron penetration depth, electron emission, and material conductivity. Based on the net surface potential’s dependence on beam current, electron range, electron emission, and conductivity, measurements of the surface potential, displacement current, and beam energy allow the charge distribution to be inferred. To take these measurements, a thin-film disordered SiO2 structure with a conductive middle layer was charged using 200-eV and 5-keV electron beams with regular 15-s pulses ...


Electron Transport Models And Precision Measurements With The Constant Voltage Conductivity Method, Justin Dekany, Jr Dennison, Alec Sim, Jerilyn Brunson Jan 2013

Electron Transport Models And Precision Measurements With The Constant Voltage Conductivity Method, Justin Dekany, Jr Dennison, Alec Sim, Jerilyn Brunson

Graduate Student Publications

Recent advances are described in the techniques, resolution, and sensitivity of the Constant Voltage Conductivity (CVC) method and the understanding of the role of charge injection mechanisms and the evolution of internal charge distributions in associated charge transport theories. These warrant reconsideration of the appropriate range of applicability of this test method to spacecraft charging. We conclude that under many (but not all) common spacecraft charging scenarios, careful CVC tests provide appropriate evaluation of conductivities down to ≈10-22 (Ω-cm)-1, corresponding to decay times of many years.

We describe substantial upgrades to an existing CVC chamber, which improved the precision ...


Methods To Determine Total Electron-Induced Electron Yields Over Broad Range Ofconductive And Nonconductive Materials, Ryan C. Hoffmann, Jr Dennison Jan 2010

Methods To Determine Total Electron-Induced Electron Yields Over Broad Range Ofconductive And Nonconductive Materials, Ryan C. Hoffmann, Jr Dennison

All Physics Faculty Publications

The electron emission properties of a material subject to incident radiation flux are key parameters in determining to what equilibrium charge a spacecraft will established under given environmental conditions. However, there is a complex relation between these emission properties and the charge built up in spacecraft insulators. Complex modeling codes have been developed to predict the potential a spacecraft will adopt as a consequence of its interaction with the space plasma. These require correct models of the electron yields as a function of charge to accurately predict the both the charge build up and the equilibrium potential of spacecraft components ...


Electric Field Induced Hopping Conductivity And Polarization In Hytrel, Steve Hart Apr 2007

Electric Field Induced Hopping Conductivity And Polarization In Hytrel, Steve Hart

Senior Theses and Projects

The focus of my 4900 research project is centered on the conductivity of Hytrel, a complex, newly developed block co-polymer. I first began to study Hytrel during the summer of 2006, as part of the USU College of Science Mini-Grant program1. My general objective was to study the relationship between the resistivity of Hytrel and hopping conductivity. Hopping conductivity is a theory of electron transport for nonconducting solids, originally developed for amorphous semiconductors2,3. The theory will be examined in greater detail later in this document. While studying this relationship last summer, I noticed an unusual phenomenon in ...


Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, Jr Dennison Jan 2007

Hopping Conductivity In Low-Density Polyethylene, Jerilyn Brunson, Jr Dennison

All Physics Faculty Publications

Measurements of resistivity of low density polyethylene (LDPE) have been made using the standard constant voltage method to determine the temperature dependence of resistivity. Where electrons are assumed to serve as the primary charge carriers, their mobility is believed to be dependent on their probability of hopping between trapping sites treated as potential wells. We consider our measurements of this relatively simple polymeric material using temperature-dependant models of conduction mechanisms developed for amorphous solids and semi-conductors.


Experimentally Derived Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. Robb Frederickson, Jr Dennison Oct 2006

Experimentally Derived Resistivity For Dielectric Samples From The Crres Internal Discharge Monitor, Nelson W. Green, A. Robb Frederickson, Jr Dennison

All Physics Faculty Publications

Resistivity values were experimentally determined using charge-storage methods for six samples remaining from the construction of the internal discharge monitor flown on the Combined Release and Radiation Effects Satellite (CRRES). Three tests were performed over a period of three to five weeks each in a vacuum of ~5times10-6 torr with an average temperature of ~25degC to simulate a space environment. Samples tested included FR4, polytetrafluoroethylene (PTFE), and alumina with copper electrodes attached to one or more of the sample surfaces. FR4 circuit-board material was found to have a dark-current resistivity of ~1times1018 Omegamiddotcm and a moderately high polarization ...


Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, Jr Dennison, A. R. Frederickson, Prasanna Swaminathan Jan 2003

Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, Jr Dennison, A. R. Frederickson, Prasanna Swaminathan

All Physics Faculty Publications

Dissipation of charges built up near the surface of insulators due to space environment interaction is central to understanding spacecraft charging. Conductivity of insulating materials is key to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. To understand these processes requires knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and charge transport within the insulator, and how the profile of trapped charge affects the transport and emission of charges from insulators. One must consider generation of mobile electrons and holes, their trapping, thermal detrapping, mobility and ...


Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, Jr Dennison, Alec Sim, J. Brunson, Eric Crapo Jan 2003

Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, Jr Dennison, Alec Sim, J. Brunson, Eric Crapo

All Physics Faculty Publications

Conductivity of insulating materials is a key parameter to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. Classical ASTM and IEC methods to measure thin film insulator conductivity apply a constant voltage to two electrodes around the sample and measure the resulting current for tens of minutes. However, conductivity is more appropriately measured for spacecraft charging applications as the "decay" of charge deposited on the surface of an insulator. Charge decay methods expose one side of the insulator in vacuum to sequences of charged particles, light, and plasma, with a metal electrode ...