Compact relativistic magnetron with gaussian beam radiation pattern

We present a compact relativistic magnetron with a simple mode converter that radiates the TE₁₁-mode when the operating mode of the magnetron is the π-mode. The magnetron used in this study has the standard A6 magnetron [1] dimensions except that the microwaves are extracted axially from a cylindrical waveguide whose radius is the same as the cavity radius. The proposed mode converter implements an anode endcap that electrically opens those cavities whose electric field distribution corresponds to the polarization of the TE₁₁-mode and closes the remaining cavities. This configuration has several advantages: 1) The TE₁₁ output mode can be easily converted into a Gaussian-like beam by means of a conical horn antenna, 2) Axial extraction of microwaves in this manner allows one to use a compact solenoid mounted directly onto the magnetron tube, thereby requiring a small volume for the applied axial magnetic field and reducing the energy requirement for the magnet system, 3) The rapidly diverging magnetic field lines from the solenoid enables a quick deposition of the downstream leakage electrons onto the waveguide, thereby protecting the dielectric window of the radiating horn antenna from electron bombardment [2].