Dynamics of Axial Mode Competition in the Gyrotron Backward-Wave Oscillator

Summary form only given. The dynamics of axial mode competition in the gyrotron backward-wave oscillator (gyro-BWO) has been investigated in theory and experiment. Because of the difference in field-shaping processes, the axial modes of the gyro-BWO each exhibit a distinctive asymmetry in field distribution along the axis. Multi-mode particle simulations reveal a consistent pattern of axial mode competition in which a fast-growing and well-established mode is subsequently suppressed by a slowly-growing mode with a favorable field profile. This is verified in a Ka-band gyro-BWO experiment. A detailed time-frequency analysis of both the simulation and experimental results further suggests that the competitiveness of a specific mode depends more on its field structure than on its initial growth rate. This perspective is expected to add a new basis for the understanding of mode competition phenomena in the gyro-BWO