Plasma-filled rippled wall rectangular backward wave oscillator driven by sheet electron beam

Abstract

Performance of the backward wave oscillator (BWO) is greatly enhanced with the introduction of plasma. Linear theory of the dispersion relation and the growth rate have been derived and analysed numerically for plasma-filled rippled wall rectangular waveguide driven by sheet electron beam. To see the effect of plasma on the TM 01 cold wave structure mode and on the generated frequency, the parameters used are: relativistic factor γ = 1.5 (i.e. v/c = 0.741), average waveguide height y 0 = 1.445 cm, axial corrugation period z 0 = 1.67 cm, and corrugation amplitude ε = 0.225 cm. The plasma density is varied from zero to 2×10 12 cm −3 . The presence of plasma tends to raise the TM 01 mode cut-off frequency (14 GHz at 2 × 10 12 cm −3 plasma density) relative to the vacuum cut-off frequency (5 GHz) which also causes a decrease in the group velocity everywhere, resulting in a flattening of the dispersion relation. With the introduction of plasma, an enhancement in absolute instability was observed.

Exact numerical solution of the dispersion relation in relativistic backward-wave oscillator and relativistic travelling-wave tube filled with plasma

“…Several papers on the theoretical analysis and simulation of the RTWT and RBWO have been published [6][7][8][9][10]. Calculation of the dispersion relation and evaluation of the growth rate are the most important aspects of analytical studies [11][12][13][14][15][16].…”

“…There is not any analytical dispersion relation in the presence of plasma, which is an anisotropic dielectric. In the theoretical methods, the Taylor approximation was used to solve the relation [12][13][14][15][16]. As a result, the growth rate and the corresponding frequencies were calculated in a small area and thus their related diagrams do not provide comprehensive information about the interaction of an electron beam with the waveguide.…”