Abstract:
In this paper, the configuration design of a novel multipacting cathode driven by pulsed power source is put forward and its dynamic process is theoretically investigated in detail. Firstly, the dynamic model is established for this novel multipacting cathode, the displacement and velocity expressions are obtained by solving the dynamic equation of secondary electrons. The influences of electron with different initial energy emitted from each direction on electron trajectory, velocity, and impact energy are discussed. The approximate expressions of electron transit time and impact energy are obtained and discussed theoretically. Secondly, to find the multipacting cathode working range, the multipacting susceptibility diagram is obtained and discussed in detail by solving electron dynamic equation coupling Vaughan's empirical formula (secondary electron yield model). Theoretical results demonstrate that the conception of the novel multipacting cathode is feasible. By applying an appropriate electric field (about MV/m) in axial and radial directions and a proper magnetic field (T) in axial direction on a cylindrical dielectric surface coated by high secondary emission yield coefficient material, the electrons move with spiral trajectories along axial direction. Electron number could be increased effectively by each impact with multipacting interaction. This phenomenon could achieve electron current amplification until multipacting comes to saturation. Finally, the deposit phenomenon of positive charges and multipacting saturation are analyzed and discussed. The roughly theoretical estimation indicates that the novel multipacting cathode has the performance of high emission current density, and the emission current density can run up to the level of kA/cm
2. Enhancing the magnitude of applied electrostatic field in radial direction can effectively improve the emission current density.