Influence of reflections of output port on stability of gyrotron traveling wave amplifier

Based on the linear theory of gyrotron traveling wave amplifier (gyro-TWA) and the boundary condition, the model of the gyro-TWA with reflections at the output port is established. The influence of the reflections on the wave gain rate, the back wave starting length and the back wave starting current for a Ka band TE01 gyro-TWA at fundamental mode is analyzed. The simulating results show that, for the TE01 mode gyro-TWA, the linear growth rate decreases, the starting length and current of the gyro-backward wave oscillation decrease but the starting frequency varies little with the increase of the tapering angle, and the increased reflection may lower the amplifier’s stability to some extent.