A proposed harmonic generator based on cyclotron waves

A cyclotron wave on a rectilinear filamentary beam can interact with a TE circuit mode of cylindrical symmetry propagating in synchronism with the beam. The interaction results in a periodic variation of the cyclotron transit angle of the electrons, causing a type of circumferential bunching which gives rise to high harmonic content. Provided the RF-field is adjusted to maximize a certain harmonic, its output power increases approximately as the square root of the harmonic number. The bunching is simply a redistribution of the relative positions of the various electrons constituting the original beam, and requires no supply of energy. All power delivered by the generator is therefore dissipated in the RF structure itself. The interaction mechanism is analyzed in detail, using two different approaches leading to the same final results. One is based on a wave description, the other considers the motion of the individual electrons. Possible applications for harmonic generation of high frequencies are discussed.