EVOLUTION OF SYMMETRICAL SOLUTIONS IN A PLASMA WITH A MODULATED KINETIC REB

A study is made of the instability of a modulated ultrarelativistic el ectron beam in a dense plasma when the phase oscillations of the beam electrons are suppressed by the relativistic increase in the electron mass, and the nonlinear saturation of the oscillation amplitude is gov erned by the dependence of the plasma permittivity on the field amplit ude. It is shown that, under these conditions, the externally modulate d beams, which can sometimes cause the conversion of the oscillation e nergy back into beam energy and prevent a transition of the system to the turbulent state, can serve as an efficient tool for controlling th e instability. Asynchronous oscillations of the beam electrons in the wave field lead to their irreversible heating and causes the kinetic s olutions to deviate from the hydrodynamic solutions describing the sol itary pulses. However, in the ultrarelativistic energy range, solution s asymptotically close to solitons can exist.