Results of testing a 3 MW, 140 GHz coaxial gyrotron

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:435471

Hogge, J P; Kreischer, K E ^[1]; Read, M E ^[2]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center
2. Physical Sciences, Inc., Alexandria, VA (United States)

The authors present experimental results of a high-power, high-frequency coaxial gyrotron. The inner conductor of a coaxial cavity influences the spectral density of the resonant modes and their corresponding quality factors. The operating mode is then chosen to remain essentially unaffected by the presence of the inner conductor, whereas competing modes see their Q lowered. As a result, multimode competition is avoided and an operating mode with a high radial index can be chosen, leading to a potentially higher output power with the same level of average ohmic losses. A coaxial gyrotron designed to produce 3 MW at 140 Ghz has been built and tested at MIT. The coaxial conductor forces some modifications in the gyrotron`s mechanical design. The presence of the inner conductor requires an inverted geometry for the electron gun, with the emitter ring located on an external anode surrounding the coaxial insert. The latter is held on both ends of the tube and is designed so that it can be retracted, thus allowing the gun to be isolated from the rest of the tube. The gun was operated at full current and voltage parameters. Due to the high sensitivity of the set-up to a misalignment of the inner conductor, the gyrotron had to be operated with a larger beam radius (9 mm instead of 8.12 mm) and a smaller pitch factor ({alpha} = 1 instead of 1.7). For these reasons, the design mode could not be excited. However, the mode selectivity of the coaxial cavity was verified, since single-mode emission has been observed on modes TE{sub 25.11}, Te{sub 26.11} and TE{sub 27.11}.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 435471
• Report Number(s): CONF-960634--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
DESIGN
ELECTRON GUNS
MICROWAVE AMPLIFIERS
MODE CONVERSION
MODE SELECTION
OPERATION
OSCILLATION MODES
PERFORMANCE