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Full-Text Articles in Physics
Time Dependent Conductivity Of Low Density Polyethylene, Phillip Lundgreen, Justin Dekany, Jr Dennison
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
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 …40>
Electron Transport Models And Precision Measurements With The Constant Voltage Conductivity Method, Justin Dekany, Jr Dennison, Alec Sim, Jerilyn Brunson
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 of …
Electron Energy Dependent Charging Effects Of Multilayered Dielectric Material, Gregory Wilson, Jr Dennison, Amberly Evans Jensen, Justin Dekany
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 at …