To the nonlinear multiharmonic theory of klystron type two-stream free electron laser

The physical analysis of two-stream superheterodyne free electron lasers (TSFELs) of the klystron type is accomplished. The multi-harmonic properties of signal, pumping, and space charge wave and the presence of a longitudinal focusing magnetic field in the system working bulk are accounted for. It is found that the main merits of the devices of the considered class are the following: compactness, extremely high level of amplification, the possibility for smooth changing working frequency, high level of input-output decoupling, capability of working at many signal-harmonics simultaneously (i.e., capability to amplify and forming signals with complex multi-harmonic spectrum, etc.).