In this paper, we propose a novel approach for the design of a virtual cathode oscillator. As a new concept, we suggest a microwave system containing an annular relativistic electron beam travelling through the drift space with dielectric inserts characterized by different values of permittivity. In this case, a virtual cathode which is the source of powerful electromagnetic oscillations forms at the junction of different dielectric materials. According to the mechanism of virtual cathode formation, we have called this device as a virpertron. We have carried out a detailed numerical investigation of virtual cathode formation features in this system via 3D electromagnetic PICsimulation using CST Particle Studio. We have also studied the spectral properties of the microwave radiation generated by the virpertron.

We report on the possibility of the beam-plasma instability development in the system with electron beam interacting with the single-component hot electron plasma without ions. As considered system, we analyse the interaction of the low-current relativistic electron beam (REB) with squeezed state in the high-current REB formed in the relativistic magnetically insulated two-section vircator drift space. The numerical analysis is provided by means of 3D electromagnetic simulation in CST Particle Studio. We have conducted an extensive study of characteristic regimes of REB dynamics determined by the beam-plasma instability development in the absence of ions. As a result, the dependencies of instability increment and wavelength on the REB current value have been obtained. The considered process brings the new mechanism of controlled microwave amplification and generation to the device with a virtual cathode. This mechanism is similar to the action of the beam-plasma amplifiers and oscillators.

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