  A nonrelativistic electron beam with a virtual cathode situated in the diode
gap with a decelerating field is experimentally and theoretically studied. A 1D
model of the electron beam in the presence of a decelerating field is
constructed. Nonlinear nonstationary processes in this system are investigated
by means of numerical analysis of the model. The processes are described and
interpreted with regard to formation and interaction of structures in the
electron flow. The theoretical results are qualitatively confirmed by the
experimental data showing that the system under study can be considered as a
promising controlled source of chaotic oscillations in the microwave range.
