Simulation of a planar radial helix slow wave structure

A planar radial helix slow wave structure based on a low loss medium is suggested. Instead of the axial, the beam-wave interaction path of this structure is on the radial direction. That is the main difference between it and most other traveling wave tubes. In this structure, a cylindrical wave has a constant radial phase velocity exists[1]. Because its cathode surface is large, high current can be taken from it with a low current density. While the current density decreases in radial direction, the space-charge parameter is small along the section of the stream[2]. The radial slow wave structure is a wideband inhomogeneous line and therefore the interaction of the radial electron stream and the higher direct and inverse harmonics decreased and even disappeared[3].