The effect of beam and plasma parameters on the four modes of plasma-loaded traveling-wave tube with tape helix

Abstract

Field theory is applied to analyze the behavior of the electromagnetic wave in the presence of a solid electron beam and magnetized plasma-loaded tape helix traveling-wave tube. The obtained dispersion relation implicitly includes azimuthal variations and all spatial harmonics of the tape helix. Results indicate that the frequency and the phase velocity of (X bp − X p ) and (O bp − X p ) modes increase with cyclotron frequency and for (O bp − O p ) and (X bp − O p ) modes decrease. In the strong magnetic field limit, the maximum growth rate and frequency of all modes are constant at different values of cyclotron frequency and beam energy. If the plasma density increases, the frequency and phase velocity of four modes will increase. The maximum growth rates of the four modes in the lower plasma density are equal and for higher values of plasma density the (O bp − X p ) mode has greatest value. The phase velocity and the frequency of (X bp − X p ) with (X bp − O p ) modes and (O bp − O p ) with (O bp − X p ) modes are coinciding with each other and for first case increase with beam density, but for latter decrease. The maximum growth rate of (O bp − O p ) mode and the maximum frequency of (X bp − X p ) mode have highest values as a function of the electron beam density.