Beam-Wave Interaction in Confocal Gyrotron Traveling Wave Tube: An Analytical and Simulation Study

The beam-wave interaction,in 170 GHz confocal gyrotron traveling wave tube(gyro-TWT),was mathematically modeled,theoretically analyzed in Nonlinear Theory derived from Generalized Transmission Line Theory,and numerically simulated for the efficiency enhancement.The original work involved the theoretically designed magnetron injection gun(MIG),mainly comprising the cathode and sectored field-emitter,for improvement of electron beam injection.The simulated results show that the self-developed MIG makes the difference.To be specific,the gyro-TWT with the self-developed MIG outperforms that with the conventional MIG for three reasons:first,the new MIG almost doubles the beam-wave interaction efficiency; second,it significantly simplifies the magnet-configuration because of the shortened interaction length; and finally,it considerably weakens the negative impact of the velocity spread.Much work remains to be done to experimentally fabricate and evaluate the theoretically designed MIG.