Contrasting ion stopping models at medium energies in partially ionized plasmas

Ion energy loss in the matter has been studied for more than a century and has been of great interest in various scientific fields [1]. The first theoretical models were the classical Bohr approximation [2], followed by the mechano-quantum, but perturbative, Bethe, and Bloch calculations for the behavior of light ions at high velocities [3,4]. Later, more elaborate approaches were developed in order to predict the behavior of higher charge states and lower velocities as well. Nowadays the stopping power of ions in solids is well understood, as it has been supported by a wealth of experimental data. Due to the remaining theoretical and experimental challenges, in addition to the scarcity of existing experimental data, the stopping power of ions in plasmas is, instead, far from being understood. However, the use of ions to heat plasmas and the characterization of plasmas by ions raises the need of understanding the interactions between particle beams and plasmas. Ion stopping power in high-density plasmas has a crucial role in the development of inertial confinement fusion (ICF). It is due to the requirement of an accurate description of the ion energy deposition in the process of heating the plasma by ions, in the ignition and combustion phases of deuterium-tritium fuel. The ion stopping power in partially ionized plasmas is currently investigated with special interest at medium projectile energies [5-7], i.e. in the energy range where a higher stopping power appears. In this region, there are still large discrepancies between the existing theoretical models, but these cannot be corroborated because there is not enough experimental data available. Different simulations of ion stopping power in partially ionized carbon plasma are presented here. The parameters of the plasma have been obtained by two-dimensional hydrodynamic simulations. Results show the differences in the stopping power predictions between the various theoretical models.



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