Dispersion properties and beam excitation of symmetric slow waves in helix traveling wave tubes in the presence of plasma

Abstract

The propagation of the hybrid slow waves in the new helix traveling wave tube, including a dielectric rod, gas plasma layer, and helix sheath is examined. It is assumed that the plasma is strongly magnetized. The dispersion relation of symmetric hybrid slow waves in this waveguide is obtained. It is shown that the frequency increases by increasing the axial wavenumber and the group velocity of slow waves reduces with increasing the dielectric constant. Moreover, by injecting the electron beam in the vacuum area in the waveguide, the symmetric hybrid slow waves are excited and the influence of various parameters on the growth rate of these waves is examined. Furthermore, therequired parameters such as plasma frequency, dielectric constant, and other geometric parameters for waveguide fabrication are expressed. According to this configuration, the allowed region for the operation of this waveguide and its growth rate and other results are obtained.