Self-excitation and establishment of generation in a two-section relativistic diffraction generator

Starting conditions for generation and features of oscillation establishment in a relativistic diffraction generator for different beam current values are numerically studied using the matrix multimode method. The efficiency boost and generation frequency stabilization are found to arise at overlap of two electron mechanisms—excitation of the fundamental oscillation of the system in the region of the 2π-type frequencies with a resonance near the cutoff frequency of the bulk mode nearest to the 2π type in a smooth waveguide.