Self-focusing of relativistic electron bunches in a dense plasma

Summary form only given. In this paper we present results of investigations on the problem of creation of ordered structures in the multipartial unstable plasma systems. It is studied to create an opportunity to control the collective dynamics of a plasma together with highly modulated relativistic electron beam. The foundation of this problem is changing sign of the Coulomb force for moving electron bunches when beam modulation frequency /spl omega/=2/spl pi/v/l is lower plasma frequency /spl omega//sub P/ (v and l are velocity and spatial period of beam). The electromagnetic radiation emitted by the beam in a plasma is a superposition of vacuum Coulomb field of moving bunches and of polarization wave excited by this field in a plasma. Under the resonance when modulation frequency is close to the Langmuir frequency focusing polarization field dominates and plasma-beam instability leads to spatial (longitudinal and transversal) compression of bunches under the action of collective field in plasma. As the density of oscillations is proportional to beam energy and density the efficiency of self-focusing increases in a case of dense relativistic beam. Our method may taken up for numerical analysis of physical experiments and development of plasma technologies using dense relativistic electron (or ion) beams with a small radial divergence like the problems of inertial controlled nuclear fusion and beam long distance transport in a dense plasma. Self-focusing of relativistic electron beam with energy E=3 mc/sup 2/ (spatial distribution of bunches in plasma at times /spl tau/=41 (a) and /spl tau/=87 (b), /spl tau/=/spl omega//sub P/t) is shown in a figure which is the result of numerical solution of Maxwell-Vlasov equations for modulated beam (numbers of plasma and beam electrons are N/sub P/=5*10/sup 5/ and N/sub b//N/sub P/=10/sup -2/).