Temporal growth rate study of a high power backward wave oscillator with semi-circularly corrugated slow wave structure

Department of Electrical and Electronic Engineering, Islamic University of Technology (IUT), Board Bazar, Gazipur 1704, Bangladesh

^a e-mail: gsaber@iut-dhaka.edu

Received: 19 January 2015
Revised: 25 March 2015
Accepted: 2 April 2015
Published online: 19 May 2015

Abstract

The dispersion properties and the temporal growth rate (TGR) of a high power backward wave oscillator (BWO) with a cylindrical metallic slow wave structure with semi-circular corrugation (SCCSWS) driven by an intense relativistic electron beam (IREB) are studied numerically. The IREB is assumed to be guided axially by an infinitely strong magnetic field. The semi-circular axial profile of the SWS is approximated by Fourier series and the study is carried out utilizing linear Rayleigh-Fourier (R-F) theory. The Fourier constants of the axial profile are determined numerically. The dispersion equation is solved numerically for the beam energy of 80–660 kV, beam current of 0.1–1.0 kA. When an electron beam with sufficient energy and current to produce instability propagates through the SWS, microwave radiation is generated. TGR which is obtained from the imaginary value of frequency and wavenumber can be used to qualitatively estimate the strength of the microwave radiation. The periodicity of the axial profile of SCCSWS is varied and the TGR for each case has been calculated by varying the beam parameters for TM₀₁ mode. The proposed structure is comparatively easy to be fabricated and expected to be useful in BWO devices for generating high power microwaves for different applications.