Design of a frequency tripling, third harmonic gyro-TWT

Summary form only given. A two-stage gyro-traveling-wave-tube(gyro-TWT) separated by a radiation-free drift section is being designed. The rf input and output sections of gyro-TWT operate at 11.5 GHz fundamental harmonic and 34.5 GHz third harmonic respectively. By choosing a proper drift section length, the third harmonic of the modulated electron beam current at the entrance to the output waveguide may be comparable to the fundamental harmonic due to the ballistic bunching of the beam in the drift section. The well prebunched beam makes beam-wave interaction in the output waveguide more efficient. The magnetic field B/sub 0/ is about 4.4 kG so that permanent magnetic packaging is possible. This type gyro-TWT features subharmonic injection, compact volume and superior stability.