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Full-Text Articles in Physics

A Simple Method For Determining Shallow Charge Distributions In Dielectrics Via Pulsed Electroacoustic Measurements, Zachary Gibson, J. R. Dennison Aug 2023

A Simple Method For Determining Shallow Charge Distributions In Dielectrics Via Pulsed Electroacoustic Measurements, Zachary Gibson, J. R. Dennison

Journal Articles

The understanding of charge dynamics in dielectric materials is paramount in mitigating electrostatic discharge events for spacecraft. The most critical spacecraft charging events are found to result from incident electrons in the energy range of 10 keV to 50 keV. The charge embedded in dielectric materials in this energy range are deposited a distance into the material on the order of a few to tens of microns. One way to measure and understand the deposited charge is via pulsed electroacoustic measurements (PEA). However, the typical PEA spatial resolution of ~ 10 μm is not sufficient to resolve or discern charge …


Relevancy Of Pulsed Electroacoustic Measurements For Investigating Spacecraft Charging, Zachary Gibson, J. R. Dennison Feb 2023

Relevancy Of Pulsed Electroacoustic Measurements For Investigating Spacecraft Charging, Zachary Gibson, J. R. Dennison

Journal Articles

The magnitude and spatial distribution of charge embedded in dielectric materials and the evolution of the charge distributions with time are paramount for the understanding and mitigation of spacecraft charging. Spacecraft materials are charged primarily by incident fluxes of low-energy electrons, with electron fluxes in the 10–50 keV range often responsible for the most deleterious arcing effects. While the pulsed electroacoustic (PEA) method can provide sensitive nondestructive measurements of the internal charge distribution in insulating materials, it has often been limited for spacecraft charging applications by typical spatial resolutions of ≤ 10 μm , with a 10- μm …


Space Environment Effects On The Electron Yields Of Ldef Thermal Control Coatings, Trace Taylor, Matthew Robertson, Heather Allen, Jr Dennison, Michael Guy, Emily Willis Feb 2023

Space Environment Effects On The Electron Yields Of Ldef Thermal Control Coatings, Trace Taylor, Matthew Robertson, Heather Allen, Jr Dennison, Michael Guy, Emily Willis

Journal Articles

Space-environment-induced degradation of white thermal control coatings from the Long Duration Exposure Facility (LDEF) was investigated. Much of the exterior of the LDEF was painted with a white thermal control coating, Aeroglaze A276; and most of the interior was coated with a black thermal control coating, Aeroglaze Z306. Outgassing from these coatings and other LDEF materials interacted with the white surface when exposed to sunlight after volatile materials condensed on the LDEF surfaces. Surface morphology was characterized by optical and scanning electron microscopies. Fourier-transform infrared spectroscopy and energy-dispersive x-ray spectroscopy were used to identify the chemical compounds and elements present …


Comparison Of Pulsed Electroacoustic Measurements And Af-Numit3 Modeling Of Polymers Irradiated With Monoenergetic Electrons, Zachary Gibson, J. R. Dennison, Brian Beecken, Ryan Hoffmann Feb 2023

Comparison Of Pulsed Electroacoustic Measurements And Af-Numit3 Modeling Of Polymers Irradiated With Monoenergetic Electrons, Zachary Gibson, J. R. Dennison, Brian Beecken, Ryan Hoffmann

Journal Articles

Successful spacecraft design and charging mitigation techniques require precise and accurate knowledge of charge deposition profiles. This paper compares models of charge deposition and transport using a venerable deep dielectric charging code, AF-NUMIT3, with direct measurements of charge profiles via pulsed electroacoustic (PEA) measurements. Eight different simulations were performed for comparison to PEA experiments of samples irradiated by 50 or 80 keV monoenergetic electrons in vacuum and at room temperature. Two materials, polyether-ether ketone (PEEK) and polytetrafluoroethylene (PTFE), were chosen for their very low conductivities so that minimal charge migration would occur between irradiation and PEA measurements. PEEK was found …