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Title: Focused cathode design to reduce anode heating during vircator operation

Abstract

Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages.

Authors:
; ;  [1]
  1. Center for Pulsed Power and Power Electronics, Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)
Publication Date:
OSTI Identifier:
22218558
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 10; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ANODES; CATHODES; CURRENT LIMITERS; DRIFT TUBES; ELECTRON BEAMS; ELECTRON EMISSION; ELECTRONS; HEATING; MICROWAVE RADIATION; OPERATION; OSCILLATORS; PLASMA DRIFT; PLASMA INSTABILITY; POTENTIALS; SPACE CHARGE

Citation Formats

Lynn, Curtis F., Dickens, James C., and Neuber, Andreas A.. Focused cathode design to reduce anode heating during vircator operation. United States: N. p., 2013. Web. doi:10.1063/1.4826209.
Lynn, Curtis F., Dickens, James C., & Neuber, Andreas A.. Focused cathode design to reduce anode heating during vircator operation. United States. doi:10.1063/1.4826209.
Lynn, Curtis F., Dickens, James C., and Neuber, Andreas A.. Tue . "Focused cathode design to reduce anode heating during vircator operation". United States. doi:10.1063/1.4826209.
@article{osti_22218558,
title = {Focused cathode design to reduce anode heating during vircator operation},
author = {Lynn, Curtis F. and Dickens, James C. and Neuber, Andreas A.},
abstractNote = {Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages.},
doi = {10.1063/1.4826209},
journal = {Physics of Plasmas},
number = 10,
volume = 20,
place = {United States},
year = {Tue Oct 15 00:00:00 EDT 2013},
month = {Tue Oct 15 00:00:00 EDT 2013}
}
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  • After repeatedly operation of a triode virtual cathode oscillator, the surface morphology of anode grid is studied by a scanning electron microscope. It is found that there are many quasi-periodic sawteeth formed on the anode grid, which are about 300-500 {mu}m in height, {approx}200 {mu}m in width, and 150-200 {mu}m in period. The formation of this sawteeth implies that there is possible Rayleigh-Taylor-like instability on the anode grid during the irradiation by high-current relativistic electron beam. These sawteeth enhance the electric field on anode grid, leading to more feasible of anode plasma generation, and more rapidly expansion of that plasma.more » As a result, the electron transmissivity of anode grid is decreased, the output microwave power of the virtual cathode oscillator is lowered and its operational performance is degraded.« less
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