Using negative electron affinity diamond emitters to mitigate space charge in vacuum thermionic energy conversion devices

A negative electron affinity (NEA) diamond surface is employed as an emitter electrode in a vacuum thermionic energy conversion device in order to mitigate the negative space charge effect. The motive diagram of an NEA device operating at the virtual saturation point is compared to a similar device...

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Bibliographic Details
Published in:Diamond and related materials 2006-11, Vol.15 (11), p.2082-2085
Main Authors: Smith, J.R., Bilbro, G.L., Nemanich, R.J.
Format: Article
Language:English
Subjects:
Applied sciences
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Cross-disciplinary physics: materials science
rheology
Device modeling
Diamond crystal
Direct energy conversion and energy accumulation
Electrical engineering. Electrical power engineering
Electrical power engineering
Electron and ion emission by liquids and solids
impact phenomena
Exact sciences and technology
Fullerenes and related materials
diamonds, graphite
Magnetohydrodynamic generators and thermionic convertors
plasma diodes
Materials science
Miscellaneous
Negative electron affinity
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Plasma devices
Specific materials
Thermionic emission
Thermionic energy conversion
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Summary:A negative electron affinity (NEA) diamond surface is employed as an emitter electrode in a vacuum thermionic energy conversion device in order to mitigate the negative space charge effect. The motive diagram of an NEA device operating at the virtual saturation point is compared to a similar device with a conventional emitter material operating in the space charge limited regime in order to understand how NEA mitigates space charge. Output current characteristics are calculated for various NEA values, and the results are compared to an ideal (no space charge) model. Increasing the value of the NEA causes the output current characteristic to approach that of the ideal model. Motive diagrams for various values of NEA are calculated and used to explain this phenomenon. It is shown that an NEA device can achieve a maximum output power density equal to the maximum output power density of a similar ideal device.
ISSN:0925-9635
1879-0062
DOI:10.1016/j.diamond.2006.09.011