Focusing and Transportation of Intense Light Ion Beam in Inertial Confinement Fusion

Abstract

The minimum requirement for the light ion beam (LIB) as the energy driver is that the instability must not grow up enough while the propagation time. The LIB will diverge by its own strong Coulomb repulsive force as it is, because the LIB is an ensemble of the charged particles. The complete charge neutralization must be required by all means. One of the way for the charge neutralization of LIB during the propagation is to fill up the reactor cavity with the inert gas of 0.1-1 Torr. The electrons in this inert gas are expected to neutralize the charge of LIB. The self-pinch propagation method has been proposed recently as a new idea. Such a propagation will be achieved by setting the ratio of the number density of background plasma to that of beam particles to be 1:10. As the current density of the beam is very intense, the self-induced magnetic field in the azimuthal direction pinches the beam itself. Because, the self-pinched plasma is not stable, the magnetic field in the axial direction to stabilize the beam is induced by the rotating motion of the beam. This magnetic field corresponds to the toroidal magnetic field in the tokamak machine. In this paper, the effects of magnetic field on the stabilization of the beam is investigated numerically as an eigenvalue problem. This is an analysis for macroscopic stabilities. The importance of the effect of electric field on the beam propagation was pointed out recently. That is, the leading- and tailing edges diverge by electric fields. These electrostatic fields are estimated on the basis of the kinetic theory and the beam divergence is calculated in the later part of the present paper.