• K P Maheshwari

      Articles written in Pramana – Journal of Physics

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

      A Hadap J Mondal K C Mittal K P Maheshwari

      More Details Abstract Fulltext PDF

      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 $\gamma = 1.5$ (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 $\epsilon = 0.225$ cm. The plasma density is varied from zero to $2\times 10^{12}$ cm-3. The presence of plasma tends to raise the TM01 mode cut-off frequency (14 GH$_z$ at $2 \times 10^{12}$ cm-3 plasma density) relative to the vacuum cut-off frequency (5 GH$_z$) 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.

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