A high-power magnetron assembly includes a high-power magnetron and a compact magnetic field generator. The high-power magnetron includes a cathode configured to emit electrons in response to receiving a supply of voltage from a power supply. The high-power magnetron includes an anode configured to concentrically surround the cathode and to attract the emitted electrons across an interaction region between the cathode and the anode. The compact magnetic field generator includes a plurality of permanent magnets including: a cathode magnet that has a longitudinal axis of symmetry annularly and that is surrounded by the cathode and disposed within the magnetron; and an anode magnet configured to annularly surround an outer perimeter of the magnetron. An arrangement of the plurality of permanent magnets concentrically about the longitudinal axis of symmetry forms a specified magnetic field within the interaction region that bounds the electrons emitted within the interaction region.