magnetron
Magnetrons are electronic components for the generation of microwaves. They are vacuum tubes consisting of cathode, cavity resonators and anode, which are enclosed by a permanent magnet.
The cathode of magnetrons is heated and for better emission of electrons it is supplied with high voltage. The permanent magnetic field directs the electrons into a circular orbit to which several resonators are connected via narrow slots. On their way to the anode, the electrons sweep along the narrow slots in the anode and excite the cavity resonators to oscillate.The microwave oscillation is coupled out via waveguides and antennas.