Design and Stability Studies of Second-Harmonic Gyro-TWT Amplifier Using Wedge-Shaped Lossy Ceramic Rod-Loaded Mode Selective RF Interaction Circuit

In this paper, the design and stability analysis of a W-band second-harmonic Gyrotron Travelling Wave Tube (gyro-TWT) amplifier loaded with the wedge-shaped lossy ceramic rods, operating in the circular azimuthally symmetric TE
₀₂
mode, has been presented. The stability of the gyroTWT has been investigated against the spurious oscillations, including the reflective oscillation, gyrotron backward oscillation (gyro-BWO), and absolute instability. The transmission loss for the operating mode has been calculated as ~19 dB/cm at 91.4 GHz for achieving the stability. Furthermore, the gyro-TWT using the distributed loaded RF section has been investigated for its nonlinear behavior using a self-consistent nonlinear analysis. The saturated RF output power of ~450 kW at 91.4 GHz with ~18% efficiency, ~30-dB saturated gain, and 3-dB bandwidth of ~3% has been achieved for an electron beam of 100 kV and 25 A.