Electrical & Computer Engineering Faculty Publications

Document Type

Article

Publication Date

6-1-2000

Abstract

We first reported the operation of a relativistic backward-wave oscillator (BWO) in the so-called cross-excitation regime in 1998. This instability, whose general properties were predicted earlier through numerical studies, resulted from the use of a particularly shallow rippled-wall waveguide [slow wave structure (SWS)] that was installed in an experiment to diagnose pulse shortening in a long-pulse electron beam-driven high-power microwave (HPM) source. This SWS was necessary to accommodate laser interferometry measurements along the SWS during the course of microwave generation. Since those early experiments, we have studied this regime in greater detail using two different SWS lengths. We have invoked time-frequency analysis, the smoothed-pseudo Wigner-Ville distribution in particular, to interpret the heterodyned signals of the radiated power measurements. These recent results are consistent with earlier theoretical predictions for the onset and voltage scaling for this instability. This paper presents data for a relativistic BWO operating in the single-frequency regime for two axial modes, operating in the cross-excitation regime, and discusses the interpretation of the data, as well as the methodology used for its analysis. Although operation in the cross-excitation regime is typically avoided due to its poorer efficiency, it may prove useful for future HPM effects studies.

Publisher

IEEE

Publication Title

IEEE Transactions on Plasma Science

ISSN

0093-3813

Volume

28

Issue

3

First Page

567

Last Page

575

DOI

10.1109/27.887675

Language (ISO)

English

Sponsorship

IEEE

Keywords

Cross-excitation instability, high power microwaves, joint time-frequency analysis, mode competition, relativistic BWO

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