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 TM01 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 y0 = 1.445 cm, axial corrugation period z0 = 1.67 cm, and corrugation amplitude e = 0.225 cm. The plasma density is varied from zero to 2 ×1012 cm − 3. The presence of plasma tends to raise the TM01 mode cut-off frequency (14 GHz at 2 ×1012 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.