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Articles 1 - 6 of 6
Full-Text Articles in Physical Sciences and Mathematics
Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, John R. Dennison, Clint Thomson
Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, John R. Dennison, Clint Thomson
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Electron emission and concomitant charge accumulation near the surface of insulators is central to understanding spacecraft charging. We present a study of changes in electron emission yields as a result of internal charge build up due to electron dose. Evolution of total, backscattered and secondary yield results over a broad range of incident energies are presented for two representative insulators, KaptonTM and Al2O3. Reliable yield curves for un-charged insulators are measured and quantifiable changes in yields are observed due to fluences. We find excellent agreement with a phenomenological argument based on insulator charging predicted by …
Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Jerilyn Brunson, John R. Dennison
Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Jerilyn Brunson, John R. Dennison
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An informal discussion of how accurate measurements of resistivity and increasing understanding of the behavior of insulating materials used on spacecraft is fundamental to advancing the design and utility of the spacecraft. Build up of charge can vary between different areas of the spacecraft, with excess charge accumulating and leading to functional anomalies or component failure. The most important parameter in determining how charge will decay through an insulator is the resistivity of the material. Current industry standards for measuring resistivity have been shown to be inconsistent with actual phenomena, and new methods of measuring resistivity must be developed and …
Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, John R. Dennison, Alec Sim, J. Brunson, Eric Crapo
Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, John R. Dennison, Alec Sim, J. Brunson, Eric Crapo
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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 …
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraftcharging, A. R. Fredrickson, John R. Dennison
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraftcharging, A. R. Fredrickson, John R. Dennison
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Novel methods have been developed to measure conductivity and charge storage in thin film insulating spacecraft materials subjected to space radiations. For a variety of such samples, conductivity values differ by up to 104 from values based on ASTM standards. Conductivity and charge storage properties are found to be functions of prior radiation history. A highly-charged insulator emits electrons for hours (Malter Effect) after the irradiation beam is turned off. Visible light can be used to induce emission from previously charged samples with shallow traps.
Instrumentation For Studies Of Electron Emission And Charging From Insulators, C. D. Thomson, V. V. Zavyalov, John R. Dennison
Instrumentation For Studies Of Electron Emission And Charging From Insulators, C. D. Thomson, V. V. Zavyalov, John R. Dennison
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Making measurements of electron emission properties of insulators is difficult since insulators can charge either negatively or positively under charge particle bombardment. In addition, high incident energies or high fluences can result in modification of a material’s conductivity, bulk and surface charge profile, structural makeup through bond breaking and defect creation, and emission properties. We discuss here some of the charging difficulties associated with making insulator-yield measurements and review the methods used in previous studies of electron emission from insulators. We present work undertaken by our group to make consistent and accurate measurements of the electron/ion yield properties for numerous …
Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, John R. Dennison, A. R. Frederickson, Prasanna Swaminathan
Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, John R. 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 …