A kinetic description of ions in aluminium wire-array precursor plasma

During the early stages of a wire-array Z-pinch implosion, low density plasma streams toward the axis by virtue of the Lorentz force. This streaming precursor plasma is initially highly collisionless and therefore cannot be modeled using standard fluid theory. A hybrid method (fluid electrons and particle ions) capable of modeling collisionless behaviour is presented. We show that the axial stagnation of the plasma flow occurs once the density becomes sufficiently high to initiate a non-linear rise in collisionality. Radiation and electron-ion energy exchange effects then result in the attainment of a dense, long-lived precursor column on axis, as observed experimentally. The column is held in place by the kinetic pressure of the streaming precursor plasma, which is balanced by the thermal pressure of the plasma in the column at the column's edge.