Harmonic mode competition in a terahertz gyrotron backward-wave oscillator

Journal Article · Mon Oct 15 04:00:00 EDT 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4757215· OSTI ID:22068839

Kao, S H; Chiu, C C; Chang, P C; Wu, K L; Chu, K R ^[1]

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1. Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

Electron cyclotron maser interactions at terahertz (THz) frequencies require a high-order-mode structure to reduce the wall loss to a tolerable level. To generate THz radiation, it is also essential to employ cyclotron harmonic resonances to reduce the required magnetic field strength to a value within the capability of the superconducting magnets. However, much weaker harmonic interactions in a high-order-mode structure lead to serious mode competition problems. The current paper addresses harmonic mode competition in the gyrotron backward wave oscillator (gyro-BWO). We begin with a comparative study of the mode formation and oscillation thresholds in the gyro-BWO and gyromonotron. Differences in linear features result in far fewer 'windows' for harmonic operation of the gyro-BWO. Nonlinear consequences of these differences are examined in particle simulations of the multimode competition processes in the gyro-BWO, which shed light on the competition criteria between modes of different as well as the same cyclotron harmonic numbers. The viability of a harmonic gyro-BWO is assessed on the basis of the results obtained.

• OSTI ID: 22068839
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 19; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTRON CYCLOTRON-RESONANCE
HARMONIC OSCILLATORS
MAGNETIC FIELDS
MASERS
NONLINEAR PROBLEMS
OSCILLATIONS
OSCILLATORS
SIMULATION
SUPERCONDUCTING MAGNETS
THZ RANGE