Generation of oscillations in a plasma filled diode

Summary form only given. A plasma-filled diode is frequently used as a model for the interaction space of a virtual cathode oscillator (vircator). A vircator is capable of generating two types of oscillations: powerful and often ill-defined oscillations based on successive appearance and disappearance of a virtual cathode, and weaker but better defined oscillations due to a flip-flop action of the space-charge. We propose to discuss the second type of oscillations. Assuming that the oscillations are harmonic we have developed an analytical model of the dynamical properties of such a system, based on a plasma-filled diode. In particular we can show that stable oscillations can be sustained by converting some of the kinetic energy of the injected beam into the electromagnetic energy of the field. The analytical results are then confirmed by more general numerical computations where no assumptions are made about the harmonic nature of the oscillations.