Analytical and Simulation Study of Multibeam Electron Generation for High Power Microwave Sources

We present a novel concept for generating multibeams (multiple electron beams) with different energies from a single cathode stalk at a single potential using two nested magnetically insulated coaxial diodes (MICDs). Particle-in-cell (PIC) simulations are performed using an actual experimental parameter-based geometry where two thin-walled intense relativistic electron beams immersed in a strong uniform magnetic field propagate through a cylindrical vacuum channel. The analytically derived results are obtained by extending Fedosov’s 1 , 2 solution for generating a hollow electron beam from a single MICD on a cathode stalk to two MICDs on a single cathode stalk at a single potential. Two electron beams are generated and accelerated downstream assuming zero initial kinetic energy of the electrons at the cathodes. Results show both electron beam currents ranging from 66 A – 2 kA with an energy difference ranging from 6 – 27% depending on the applied potentials which range from 100-600 kV and the geometry of the two MICDs. An optimal geometry is a crucial factor in achieving the maximum energy difference between the electron beams for comparable currents. The analytical and numerical simulation results show good agreement. We are currently in the process of planning experiments using the SINUS-6 electron beam accelerator to validate the theoretical and simulation results. These results will be used to design a multibeam TWT based on the theory of Figotin. 3