A Study on Instabilities of 220 GHz Confocal Waveguide Gyro-TWT

Instability problem is one of the most significant limits for high power gyro-TWTs. In this paper, the absolute instabilities and backward wave oscillation (BWO) instabilities of a 220 GHz confocal waveguide gyro-TWT are discussed. The results show that the starting current of absolute instabilities is much higher than the operating current 5A, and the critical interaction length of HE05 mode backward wave oscillation is about 10mm.