Small-Signal Theory of the Gyrotron Amplifier with a Zigzag Quasi-Optical System

We describe the small-signal theory of a travelling-wave-tube (TWT) gyro-amplifier with a sectioned system of quasi-optical mirrors ensuring the zigzag path of the operating wave beam. Our consideration is limited within the range of parameters corresponding to the situation where the parasitic self-excitation of backward-wave-type oscillations is impossible. In this situation, a high-gain amplifier can be realized in a system of isolated free-from-self-excitation “clusters” consisting of several mirror sections. We show that the characteristics of this amplifier are weakly dependent on the number of sections in the cluster.