Mode coupling in coaxial waveguides with varying-radius center and outer conductors

Journal Article · Wed Mar 01 04:00:00 EST 1995 · IEEE Transactions on Microwave Theory and Techniques

DOI:https://doi.org/10.1109/22.372104· OSTI ID:46097

Shafii, J; Vernon, R J ^[1]

---

1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

Gyrotrons have been used to heat magnetically confined plasmas encountered in fusion research at the electron-cyclotron-resonance frequency. High-power millimeter-wave gyrotrons have recently been designed with highly overmoded coaxial resonators. It has been shown that the inclusion of an inner conductor in the gyrotron`s cavity can reduce mode competition and hence may lead to more stable operation in the desired mode in the cavity by moving the resonant frequencies of competing modes. In this paper, the mode conversion process in a coaxial waveguide with varying-radius center and outer conductors is shown to be described by a system of first-order differential equations-the coupled mode equations. The nondiagonal coefficients of this system are called the coupling coefficients. In this paper, the authors derive the explicit expressions for the coupling coefficients in a varying radius coaxial waveguide and discuss some of their important features. These coefficients can be used in determining model conversion in a coaxial cavity with slowly varying walls or designing and analyzing coaxial waveguide tapers and mode converters. Some experimental results of the coupling coefficients for the case of azimuthally symmetric modes, TE{sub on} modes, are also given.

• DOE Contract Number: FG02-85ER52122
• OSTI ID: 46097
• Journal Information: IEEE Transactions on Microwave Theory and Techniques, Journal Name: IEEE Transactions on Microwave Theory and Techniques Journal Issue: 3 Vol. 43; ISSN IETMAB; ISSN 0018-9480
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CAVITY RESONATORS
ECR HEATING
MICROWAVE AMPLIFIERS
MODE CONVERSION
THERMONUCLEAR DEVICES
WAVEGUIDES