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Title: Stable coaxial-waveguide gyrotron backward-wave oscillator with distributed losses

Abstract

This study analyzes the performance of a coaxial-waveguide gyrotron backward-wave oscillator (gyro-BWO) operating at the fundamental harmonic by considering mode competition, which may be attributed to higher-order axial modes and competing transverse modes. In the coaxial waveguide with a short length and uniform cross section, the threshold currents of the higher-order axial modes are substantially higher than the operating current. Additionally, when the beam voltage or the magnetic field is adjusted, the oscillation that neighbors the minimum start-oscillation current of a transverse mode has a positive-k{sub z} field profile, and is excited near the cutoff frequency. As a result, the distributed wall losses at the downstream end of the interaction structure effectively damp the positive-k{sub z} field, and raise significantly the minimum start-oscillation currents of the competing transverse modes. This study also investigates how the parameters, including lossy section length, outer wall resistivity, inner wall resistivity, and ratio of the outer radius to the inner radius, affect the start-oscillation currents of the competing transverse modes in order to obtain stable operation conditions in the frequency tuning range. As is forecasted, when using a 15 A electron beam, the Ka-band coaxial gyro-BWO produces an output power of 137 kW and 3more » dB bandwidth of 4.2% by magnetic tuning and an output power of 145 kW and 3dB bandwidth of 2.0% by beam voltage tuning.« less

Authors:
 [1]
  1. Department of Communication Engineering, National Penghu University of Science and Technology, Penghu 880, Taiwan (China)
Publication Date:
OSTI Identifier:
21421281
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 17; Journal Issue: 10; Other Information: DOI: 10.1063/1.3486529; (c) 2010 American Institute of Physics; Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELECTRON BEAMS; MICROWAVE AMPLIFIERS; OSCILLATIONS; OSCILLATORS; THRESHOLD CURRENT; WAVEGUIDES; AMPLIFIERS; BEAMS; CURRENTS; ELECTRIC CURRENTS; ELECTRONIC EQUIPMENT; EQUIPMENT; LEPTON BEAMS; MICROWAVE EQUIPMENT; PARTICLE BEAMS

Citation Formats

Hung, C L. Stable coaxial-waveguide gyrotron backward-wave oscillator with distributed losses. United States: N. p., 2010. Web. doi:10.1063/1.3486529.
Hung, C L. Stable coaxial-waveguide gyrotron backward-wave oscillator with distributed losses. United States. https://doi.org/10.1063/1.3486529
Hung, C L. 2010. "Stable coaxial-waveguide gyrotron backward-wave oscillator with distributed losses". United States. https://doi.org/10.1063/1.3486529.
@article{osti_21421281,
title = {Stable coaxial-waveguide gyrotron backward-wave oscillator with distributed losses},
author = {Hung, C L},
abstractNote = {This study analyzes the performance of a coaxial-waveguide gyrotron backward-wave oscillator (gyro-BWO) operating at the fundamental harmonic by considering mode competition, which may be attributed to higher-order axial modes and competing transverse modes. In the coaxial waveguide with a short length and uniform cross section, the threshold currents of the higher-order axial modes are substantially higher than the operating current. Additionally, when the beam voltage or the magnetic field is adjusted, the oscillation that neighbors the minimum start-oscillation current of a transverse mode has a positive-k{sub z} field profile, and is excited near the cutoff frequency. As a result, the distributed wall losses at the downstream end of the interaction structure effectively damp the positive-k{sub z} field, and raise significantly the minimum start-oscillation currents of the competing transverse modes. This study also investigates how the parameters, including lossy section length, outer wall resistivity, inner wall resistivity, and ratio of the outer radius to the inner radius, affect the start-oscillation currents of the competing transverse modes in order to obtain stable operation conditions in the frequency tuning range. As is forecasted, when using a 15 A electron beam, the Ka-band coaxial gyro-BWO produces an output power of 137 kW and 3 dB bandwidth of 4.2% by magnetic tuning and an output power of 145 kW and 3dB bandwidth of 2.0% by beam voltage tuning.},
doi = {10.1063/1.3486529},
url = {https://www.osti.gov/biblio/21421281}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 10,
volume = 17,
place = {United States},
year = {Fri Oct 15 00:00:00 EDT 2010},
month = {Fri Oct 15 00:00:00 EDT 2010}
}