Ion front acceleration in collisional nonthermal plasma
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Ion front acceleration in collisional nonthermal plasma Djemai Bara1,a , Mohamed Faouzi Mahboub2 , and Djamila Bennaceur-Doumaz1 1 2
Centre de D´eveloppement des Technologies Avanc´ees, B.P. 17 Baba Hassen, 16303 Algiers, Algeria Theoretical Physics Laboratory, Faculty of Physics USTHB, B.P. 32 El Alia, Algiers 16079, Algeria Received 14 February 2020 / Received in final form 30 May 2020 / Accepted 17 September 2020 Published online 1 November 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 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.
1 Introduction Ultra-high intensity lasers interacting with solid foils produce accelerated proton or heavy ion beams. Among the several acceleration mechanisms studied in the literature, the Target Normal Sheath Acceleration (TNSA) mechanism, proposed by Wilks et al. [1] is the most widely investigated in ion acceleration. In this mechanism, laser pulses interact with plasmas and generate hot electrons that are transported to the target rear surface. A sheath electric field is formed there, which then accelerates the ions in the target normal direction. These ion beams have remarkable properties to allow their potential applications in ion radiography [2], fusion energy [3], and medical therapy [4]. However, in practice, some applications require higher ion energies, small ion spatial divergence, and low ion energy spread. It is for these reasons that the ion front of plasma expansion in intense laser-matter interaction, the position where the ion energies and the electric field amplitude reach their maximum values, has been the subject of many studie
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