Theory of the Harmonic Multiplying Gyrotron Traveling Wave Amplifier

The nonlinear processes taking place in the harmonic multiplying gyrotron traveling wave amplifier are analyzed. By amplifying a drive wave through interaction at the fundamental cyclotron harmonic frequency, the beam-embedded nonlinear signal at a harmonic frequency is amplified through subsequent harmonic interaction. The analysis elucidates physical properties of importance, such as the interference from the lower harmonic perturbations, power/gain scaling, and the phase relation between the drive and harmonic waves. These properties are found to be basically different from those of single-frequency amplifiers.