Nonlinear theory of large-signal mode locking in a gyrotron oscillator

Alan H. McCurdy; Hao Wu

doi:10.1117/12.218575

8 September 1995 Nonlinear theory of large-signal mode locking in a gyrotron oscillator

Alan H. McCurdy, Hao Wu

Proceedings Volume 2557, Intense Microwave Pulses III; (1995) https://doi.org/10.1117/12.218575
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

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 TE_11n and TE_01n 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.

Citation Download Citation

Alan H. McCurdy and Hao Wu "Nonlinear theory of large-signal mode locking in a gyrotron oscillator", Proc. SPIE 2557, Intense Microwave Pulses III, (8 September 1995); https://doi.org/10.1117/12.218575

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