Physics Student Research

Document Type

Presentation

Journal/Book Title/Conference

Spacecraft Charging Technology Conference (2022)

Location

Virtual

Publication Date

4-4-2022

Abstract

The magnitude and spatial distribution of charge embedded in dielectric materials and the evolution of the charge distributions with time are at the heart of understanding spacecraft charging. Spacecraft materials are charged primarily by incident fluxes of low energy electrons, with electron fluxes in the 10 keV to 50 keV range often responsible for the largest deleterious arcing effects. While the pulsed electroacoustic (PEA) method can provide sensitive non-destructive 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 range of electrons in common spacecraft materials (e.g., PEEK, PTFE, LDPE or SiO2) at energies from ~20 keV to ~40 keV. To investigate the relevance of the PEA method for typical spacecraft charging applications, a series of PEA tests over a range of incident electron energies were devised. Samples of thin film polyether-etherketone (PEEK), having undergone vacuum bake out, were irradiated with mono-energetic electron beams with energies from 10 keV to 80 keV. PEEK was chosen as the test material since its very low conductivity meant that deposited charge can be considered stationary for the timescale of the PEA experiments. The relatively low acoustic attenuation and dispersion of PEEK allows for more accurate PEA measurements of the internal charge distribution. PEA measurements were used to determine the magnitude of deposited charge and the peak positions as means to determine the minimum incident energies for which PEA measurements provided meaningful results. The results of the study were thus used to characterize the merits of PEA measurements over energy ranges of relevancy to spacecraft charging issues.

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