Structure & Principle of operation

A gyrotron consists of an electron gun, a cavity resonator, a mode converter, an output window and a collector, and requires a solenoid magnet to give a gyrating motion to the electron beam.

Electrons emitted from a cathode under the action of the electric field, move in a gradually increasing magnetic field towards the cavity. In this motion, part of energy of the electron motion along the lines of magnetic field is transformed into energy of gyration.

Electrons that have a cyclotron frequency slightly below the resonant frequency of the microwave excited in the cavity are bunched and decelerated by its transverse electric field.

As a result, the microwave is given the gyration energy by the bunched electrons and induces oscillation. The microwave generated within the cavity mode is converted to a wave beam by the mode converter, shaped by some mirrors, and output through the output window.