Theoretical Analysis of the Hollow Electron Beam Interaction With Electromagnetic Waves in a Partially Thermal Plasma-Loaded Helix

The linear theory of the interaction of electromagnetic waves in a helix slow wave structure filled with thermal plasma driven by an electron beam is investigated. The dispersion relation is found by the application of boundary conditions. This dispersion equation determines the propagation and the gain of the modes in the plasma loaded helix-type traveling-wave tube. The complex transcendental method is used for the solution of the dispersion relation. The role of plasma temperature and the trend of change for the electron beam velocity on the gain were also evaluated. The results show that the growth rate is enhanced with plasma temperature, and the strong gain maximums are for the hybrid mode frequencies. It has also been shown that if the electron beams velocity decrease in the system, the growth rate will increase.