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

Abstract

A physical model based on a Monte Carlo approach is proposed to calculate the ionization dynamics of hot-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 are taken into consideration self-consistently. When compared with other models, which are applied in the literature for plasmas near thermal equilibrium, the temporal relaxation of ionization dynamics can also be simulated by the proposed model. Besides, this model is general and can be applied for both single elements and alloys with quite different compositions. The proposed model is implemented into a PIC code, with (final) ionization equilibriums sustained by competitions between CI and its inverse process (i.e., RE). Comparisons between the full model and model without IPD or RE are performed. Our results indicate that for bulk aluminium at temperature of 1 to 1000 eV, (i) the averaged ionization degree increases by including IPD; while (ii) the averaged ionization degree is significantly over estimated when the RE is neglected. A direct comparison from the PIC code is made with the existing models for the dependence of averaged ionization degree on thermal equilibrium temperatures and shows good agreements with that generated from Saha-Boltzmann model and/or FLYCHK code.

Diagnosis of fast electron transport by coherent transition radiation

“…Besides, the ionization model in LAPINS includes field ionization, collision ionization, electron-ion recombination and ionization potential depression. This model can not only be applied for plasmas near thermal equilibrium, but also can be used in relaxation process of ionization dynamics [34]. After considering the collision effect and ionization effect, our PIC simulations are very close to the real situation.…”

“…The simulations are carried out with the PIC code LAPINS developed by one of the authors. LAPINS is an implicit PIC code [32] which includes collision [33], ionization [34,35], radiation [36], strong field quantum electrodynamics (QED) [37] and nuclear reaction [38]. Because of the amount of calculation, we decided to use a thin target for simulation and diagnose the terahertz radiation, so as to obtain the CTR distribution of 2D and 3D simulations.…”

The role of collisional ionization in heavy ion acceleration by high intensity laser pulses

“…Last but not least, the process that counteracts ionization is recombination , which is not accounted for in EPOCH and might be important. Recombination is mostly believed not to be important in a few ps after laser-target interaction 22 , but some studies have shown that the absence of that makes a clear difference to the final charge states of ions and to the temporal evolution of ionization 23 , 24 . Recombination of ions can occur via free or bound electrons.…”

Periodic spectral modulations of low-energy, low-charge-state carbon ions accelerated in an intense laser–solid interaction

“…In order to confirm the influence of laser intensity on ionization of carbon species, for both focused and defocused configurations, we carried out 2D numerical simulations using the PIC program LAPINE, 23 which includes both ionization and collision dynamics. 24,25 In the simulations, the laser wavelength was taken as 0.8 lm. The dimensionless maximum amplitude of the laser electric field was taken as a 0 ¼ 5 for the intensity at tight focus and a 0 ¼ 1 for the intensity in the defocused configuration.…”