Study of Beam-Wave Interaction in a 170-GHz Confocal Gyrotron Traveling-Wave Tube

Confocal gyrotron traveling-wave tube (gyro-TWT) is a novel gyrotron amplifier capable of operating in higher order modes while generating high power at the same time. So far, confocal gyro-TWT has been studied by MIT both in theory and experiment at 140 GHz. In this paper, a center frequency of 170-GHz TE06-mode confocal gyro-TWT is designed theoretically, and it features high power and broadband capabilities. Theoretical investigation predicts that, when the magnetic injection gun is optimized to generate an electron beam of 65 kV, current of 7 A, with a pitch factor of 1.2, this gyro-TWT is of an excellent performance. At a given operating magnetic field of 6.11 T, with an input power of 10 W, a saturated gain of at least 30 dB, 3-dB bandwidth of over 4 GHz and highest efficiency of 17.1% are achieved.