Effect of the ionization process on the focusing of a relativistic electron beam by a gas-plasma lens

A numerical simulation is made of the processes occurring in a plasma lens under conditions when the focusing of a relativistic electron beam is strongly affected by the ionization of the residual gas in the lens region by the beam itself. The paraxial, azimuthally symmetric, 1.5-dimensional, electrostatic kinetic model, taking account of plasma production, expansion of the plasma electrons away from the beam region, and contraction of the ions toward the axis of the beam, was used for the calculation. The dynamics of the formation of a focal spot is studied, and the size and position of the spot are determined as functions of time for different values of the gas pressure, initial plasma density, and energy of the beam electrons. Zh. Tekh. Fiz. 67, 90–94 (October 1997)