Effects of diode current on high powermicrowave generation in a vircator

摘要

An experiment of a virtual cathode oscillator (vircator) built on thelow impedance intense electron beam accelerator Flash II is reported. A novelspectrum diagnosis method—a circulating dispersion line—is proposed. A thin oillayer coated graphite cathode is introduced in the experiment to decrease the delaytime of the explosive emission process and obtain a homogeneous electron beamemission for improving the high-power microwave (HPM) generation efficiency. Theeffect of diode current on HPM generation in the vircator system is discussed. TheHPM pulse width has a strong connection with the diode current waveform. Formost shots, corresponding to the time that microwave emission starts, there isan inflection point in the diode current pulse. Compared with the case that nomicrowave is generated, the diode current increases more slowly following theinflection point. HPM generation terminates when the beam current reaches theself-pinching critical current of the diode.