magnetron (măgˈnĭtrŏnˌ) [key], vacuum tube oscillator (see electron tube) that generates high-power electromagnetic signals in the microwave frequency range. Its operation is based on the combined action of a magnetic field applied externally and the electric field between its electrodes. The tube is a diode having a cathode and an anode and is surrounded by an external magnet. Without this external magnetic field, the tube would work much like a simple diode, with the electrons flowing directly from the cathode to the anode. The magnetic field forces the cathode-emitted electrons to assume a curved path and thus creates a rotating electron cloud about the tube axis. The magnetron is noted for its high efficiency (ability to convert electrical power input to microwave power output). Magnetrons are available for generating microwave energies ranging from a few kilowatts to a few megawatts and are used extensively in radar systems and microwave ovens.