Monte Carlo approach to calculate ionization dynamics of hot solid-density plasmas within particle-in-cell simulations

摘要

A physical model based on a Monte Carlo approach is proposed to calculate the ionization dynamics ofhot-solid-density plasmas within particle-in-cell (PIC) simulations, and where the impact (collision) ionization(CI), electron-ion recombination (RE), and ionization potential depression (IPD) by surrounding plasmas aretaken into consideration self-consistently.When compared with other models, which are applied in the literaturefor plasmas near thermal equilibrium, the temporal relaxation of ionization dynamics can also be simulated by theproposed model. Besides, this model is general and can be applied for both single elements and alloys with quitedifferent compositions. The proposed model is implemented into a PIC code, with (final) ionization equilibriumssustained by competitions between CI and its inverse process (i.e., RE). Comparisons between the full modeland model without IPD or RE are performed. Our results indicate that for bulk aluminium at temperature of 1 to1000 eV, (ⅰ) the averaged ionization degree increases by including IPD; while (ⅱ) the averaged ionization degreeis significantly over estimated when the RE is neglected. A direct comparison from the PIC code is made withthe existing models for the dependence of averaged ionization degree on thermal equilibrium temperatures andshows good agreements with that generated from Saha-Boltzmann model and/or FLYCHK code.