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Effects of Incident Electron Fluence and Energy on the Election Yield Curves and Emission Spectra of DielectricsWe present an experimental study of evolution of electron emission yields and spectra as a result of internal charge build up due to electron dose. Reliable total, backscattered and secondary yield curves and electron emission spectra for un-charged insulators using a low fluence, pulsed electron beam (= or < 5 microsec at = or < 3 nA/sq mm or = or < 10(exp 5) e/sq mm per pulse) with low energy electron and UV flooding to neutralize the charging between pulses. Quantifiable changes in yield curves are observed due to < 100 fC/sq mm fluences for several excellent dielectric thin film materials. We find good agreement with a phenomenological argument based on insulator charging predicted by the yield curve; this includes an approximately linear decrease in the magnitude of the yield as incident energies approach the crossover energies and an exponential decrease in yield as accumulated internal charge reduces the landing energy to asymptotically approach a steady state surface charge and unity yield. We also find that the exponential decay of yield curves with fluence exhibit an energy dependent decay constant, alpha(E), over a broad range of incident energies below, between and above the crossover energies. Finally, we present some preliminary physics-based models for this energy dependence and attempt to relate our charging measurements to knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and transport, and how the profile of trapped charge affects the transport and emission of charges from insulators.
Document ID
20050167058
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Sim, Alec
(Utah State Univ. United States)
Dennison, J. R.
(Utah State Univ. United States)
Thomson, Clint
(ATK-Thiokol Propulsion Brigham City, UT, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Subject Category
Solid-State Physics
Meeting Information
Meeting: Annual American Physical Society March Meeting
Location: Los Angeles, CA
Country: United States
Start Date: March 21, 2005
End Date: March 25, 2005
Sponsors: American Physical Society
Funding Number(s)
CONTRACT_GRANT: NAS8-03082
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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