Distribution of the axial electric field in a helix travelling wave tube filled with plasma

A plasma loaded helix type slow wave structure is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated along radial into three regions. By means of sheath model and the Maxwell´s equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analyzed respectively in different plasma densities and plasma column radius by numerical computation. Some useful results are obtained on the basis of the discussion.