Ion front acceleration in collisional nonthermal plasma

Abstract

A three fluid-model consisting of electrons, ions, and neutral atoms including source terms of ionization and recombination is used to study the ion front evolution in an intense-laser created plasma. A parametric study for the ion front profiles as a function of electron nonthermality and trapping in the presence of different source terms is performed. The numerical results show that the ion front profiles are significantly affected by the nonthermal and trapping effects. In the case of ionization alone, these effects favor the stability of the ion acceleration process interpreted from the plateau appearing in the ion front profiles, whereas the case of recombination alone shows a more important ion beam energy. On the other hand, taking into account both ionization and recombination processes in the same nonequilibrium plasma model is more adequate to obtain highly monoenergetic ion beams. In addition, the same study is performed for three different target materials, H, C, and Al. It is found that proton and carbon ion energy profiles present a good trend and the same ion front position behaviors, unlike aluminum ion which show a slower acceleration. This work is motivated to improve the understanding and predictive capability of electron nonthermality, trapping and collision effects on the ion front profiles in high-intensity laser-plasma acceleration.