Target ionization by a high current relativistic monoenergetic electron beam

The propagation through an insulator of a high-current monoenergetic fast electron beam is investigated in a one-dimensional model. The target ionization provides the charge and current neutralization and enables the beam propagation. The ionization process consists of two stages: (i) the self-consistent electric field ionization of atoms in the beam front and (ii) the collisional ionization of atoms by the return current in the beam body. The ionization in the beam front defines the propagation velocity. The charge neutralization quickly suppresses the electric field behind the beam front and the plasma heating by the return current supports the collisional ionization in the beam body. This constitutes the main mechanism of the energy loss for high beam densities.