Ionization and recombination effects on laser ion acceleration in a finite mass plasma expansion

Abstract

A self-similar multi-fluid model is performed to describe ion acceleration in singly ionized plasma with nonthermal electrons, where ionization and recombination are considered. It is found that ion acceleration in plasma expansion is strongly influenced by the competition of ionization and recombination processes under different nonthermal effects, at electron temperatures, and for various target materials. Two phases of expansion are shown in the profiles. The first one is the strongest collisional dense plasma that is created, spreading smoothly into vacuum near the surface of the target, with low slopes in all ion expansion profiles. The second is the core or the central phase of expansion dominated by recombination processes, with steep slopes up to the expansion front position, where the ion velocities and the electric field amplitude have reached their maximum values. The limit of expansion is determined where the ion density and electric field vanish. The interest of such a study may concern the dynamics of ionization and recombination processes in laser-plasma acceleration where nonthermal, energetic electrons are present.