A 0.2-THz second-harmonic coaxial-waveguide gyrotron traveling-wave-tube amplifier

High-harmonic operation is of practical importance for THz gyrotrons because the required magnetic field is significantly reduced. However, spurious oscillations are a severe problem in the development of a harmonic gyrotron traveling-wave-tube (gyro-TWT) amplifier in THz region. This study exams the possibility of using a coaxial waveguide as the interaction structure of a THz second-harmonic gyro-TWT. To improve the stability of this device, the inner and outer cylinders of the coaxial interaction waveguide are applied with distributed losses. The achieved performance of the gyro-TWT amplifier, including the output power, efficiency, gain and bandwidth, are predicted.