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Proceedings Paper

Nonlinear theory of large-signal mode locking in a gyrotron oscillator
Author(s): Alan H. McCurdy; Hao Wu
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Paper Abstract

Nonlinear, time-dependent calculations have been carried out for closed-cavity gyrotron oscillations using a strongly modulated electron beam. It is found that radiation pulses of width 200 ps can be generated with carrier frequency of 18 GHz at over 10% efficiency. The gyrotron features a tapered wall radius to allow an equidistant spectrum of cavity modes. Evidence of a disruption in locking is found at electron beam currents several times the start oscillation value. Applications for short pulse radiation in the millimeter and submillimeter wavelength range include radar, Fourier transform spectroscopy, plasma diagnosis, and time domain metrology. It is shown here that extremely short radiation pulses, at kilowatt power levels and high efficiency, may be obtained by mode locking a tapered cavity gyrotron using an electron beam with a modulated current density. A nonlinear time-dependent theory and particle-in-cell simulations are used to analyze the device. The two theoretical approaches assume TE11n and TE01n modes, respectively, which are excited by an electron cyclotron electron beam wave which is matched in phase and group velocity to these modes. The design of the oscillator cavity is outlined, as well as mode locking results as a function of beam current pulsewidth, pulse repetition frequency and amplitude.

Paper Details

Date Published: 8 September 1995
PDF: 12 pages
Proc. SPIE 2557, Intense Microwave Pulses III, (8 September 1995); doi: 10.1117/12.218575
Show Author Affiliations
Alan H. McCurdy, Univ. of Southern California (United States)
Hao Wu, Univ. of Southern California (United States)

Published in SPIE Proceedings Vol. 2557:
Intense Microwave Pulses III
Howard E. Brandt, Editor(s)

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