Research on TEM mode feedback and distributed reflection for high-power output of a V-band transit-time oscillator under a low guiding magnetic field

Abstract

A novel V-band relativistic coaxial transit time oscillator (RCTTO) is proposed to operate with high efficiency under a low magnetic field. A two-stage cascade buncher, a TEM mode feedback mechanism, and a distributed reflector are proposed in the design of the V-band RCTTO to study electron beam modulation, microwave transmission, and microwave output. The two-stage cascade buncher enhances the velocity modulation of the electron beam. The TEM mode feedback mechanism improves the modulation effect of the second buncher by strengthening the gap voltage of the second buncher and deepening the fundamental harmonic current modulation depth. The distributed reflector can isolate the TEM mode leakage into the diode region and minimize the disturbance to the electron beam generation and transmission. With an input diode voltage of 391 kV, beam current of 4.91 kA, and low guiding magnetic field of 0.6 T, the RCTTO outputs a microwave with an average power of 658 MW and a frequency of 58.62 GHz, resulting in a high conversion efficiency of 34.3%.