S Saviz - Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran

Field theory is applied to analyze the behavior ofthe electromagnetic wave in the presence of a solid electronbeam and magnetized plasma-loaded tape helix travelingwavetube. The obtained dispersion relation implicitlyincludes azimuthal variations and all spatial harmonics of thetape helix. Results indicate that the frequency and the phasevelocity of (X(bp) - X(p)) and (O(bp) - X(p)) modes increase withcyclotron frequency and for (O(bp) - O(p)) and (X(bp) - O(p))modes decrease. In the strong magnetic field limit, the maximumgrowth rate and frequency of all modes are constant atdifferent values of cyclotron frequency and beam energy. Ifthe plasma density increases, the frequency and phase velocityof fourmodes will increase. The maximumgrowth rates of thefour modes in the lower plasma density are equal and forhigher values of plasma density the (O(bp) - X(p)) mode hasgreatest 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 firstcase increase with beam density, but for latter decrease. Themaximumgrowth rate of (O(bp) - O(p))mode and the maximumfrequency of (X(bp) - X(p)) mode have highest values as afunction of the electron beam density.

Traveling wave tube Helix Plasma