Selfconsistent modeling of terahertz waveguide and cavity with frequencydependent conductivity
Abstract
The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, highfrequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequencydependent complex quantity commonly used to treat electromagnetics of metals at optical frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of highpower THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a selfconsistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DCconductivity model. The reduction in Ohmic losses undermore »
 Authors:
 Department of Physics, National Taiwan University, Taipei, Taiwan (China)
 IHM and IHE, Karlsruhe Institute of Technology, Karlsruhe (Germany)
 Publication Date:
 OSTI Identifier:
 22408020
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; Other Information: (c) 2015 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; ATTENUATION; COMPUTERIZED SIMULATION; ELECTRIC CONDUCTIVITY; ELECTRONS; FREQUENCY DEPENDENCE; HEAT LOSSES; INTERACTIONS; MICROWAVE AMPLIFIERS; MICROWAVE RADIATION; MINIMIZATION; POLARIZED BEAMS; QUALITY FACTOR; ROUGHNESS; THZ RANGE; ULTRAVIOLET RADIATION; WAVEGUIDES
Citation Formats
Huang, Y. J., Chu, K. R., Email: krchu@yahoo.com.tw, and Thumm, M. Selfconsistent modeling of terahertz waveguide and cavity with frequencydependent conductivity. United States: N. p., 2015.
Web. doi:10.1063/1.4905627.
Huang, Y. J., Chu, K. R., Email: krchu@yahoo.com.tw, & Thumm, M. Selfconsistent modeling of terahertz waveguide and cavity with frequencydependent conductivity. United States. doi:10.1063/1.4905627.
Huang, Y. J., Chu, K. R., Email: krchu@yahoo.com.tw, and Thumm, M. 2015.
"Selfconsistent modeling of terahertz waveguide and cavity with frequencydependent conductivity". United States.
doi:10.1063/1.4905627.
@article{osti_22408020,
title = {Selfconsistent modeling of terahertz waveguide and cavity with frequencydependent conductivity},
author = {Huang, Y. J. and Chu, K. R., Email: krchu@yahoo.com.tw and Thumm, M.},
abstractNote = {The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, highfrequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequencydependent complex quantity commonly used to treat electromagnetics of metals at optical frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of highpower THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a selfconsistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DCconductivity model. The reduction in Ohmic losses under the ACconductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.},
doi = {10.1063/1.4905627},
journal = {Physics of Plasmas},
number = 1,
volume = 22,
place = {United States},
year = 2015,
month = 1
}

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