Investigation of the Poynting flux ratio in the helix traveling wave tube

The study deals with amplification of a propagating slow wave interacting with an annular hollow electron beam in a helix slow wave structure (SWS). The role of thermal plasma density in a ratio of the axial pointing flux in the plasma region is also investigated. This ratio is small for lower plasma densities. The effects of the variations of the hollow electron beam velocity on the normalized growth rate and the poynting flux ratio at the hybrid mode frequency are presented. The maximum gain is obtained in the frequency of hybrid mode and the poynting flux ratio reaches its maximum value at the hybrid mode frequency. Also is analyzed the trend of changes for the normalized growth rate for a different beam velocities. The results show that for all beam velocities the maximum growth rate is for hybrid mode frequencies. The numerical method used in this paper is complex transcendental.