Axial Feedback Vircator Studied And Improved

The virtual cathode oscillator (vircator) is one of the most important devices that can produce high power microwaves. For the increasing of microwave power and the locking of operation frequency, researchers have proposed many different types of improved vircators. In this paper, an axial vircator with feedback annulus is studied in the following three aspects:First, the characteristics of the vircator is simulated by a dimension, fullyelectromagnetic and relativistic particle-in-cell code. The relations between microwave power and operation frequency and the cathode-anode gap are studied in detail. It is found that the dominant microwave frequency is approximately unchanged at around 3.5GHz or at around 4.8GHz with the cathode-anode gap greater or less than 1.3cm in our model, respectively. The experimental results confirm the conclusion. And a reasonable explanation is put forward.Next, the effects of the electron-beam quality on the characteristics of the vircator are investigated with simulation method. The simulation results show that the front edge of the beam pulse has almost no effect on the saturated microwave output, while good front edges can accelerate the saturation of the virtual cathode oscillation, and beam quality(except its energy spread) has almost no effect on microwave frequency, and so on.Finally, a new axial vircator with improved feedback annulus is studied and designed through particle simulation. And the way to suppress the harmonic with improved feedback annulus is also analyzed theoretically. At the same time, in order to increase the gain of the radiation aperture, a new way to enlarge the waveguide radius is presented. And a gigawatt level of averaged output power with quasi-single TMoi mode is obtained at 3.9GHz under the diode voltage of 550kV and the beam current of 23kA. Another type of improved vircator is also presented, and satisfactory results are also achieved.