Numerical simulation of nanosecond laser ablation and plasma characteristics considering a real gas equation of state

Abstract

Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma, a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen layer and plasma shielding effect is developed. The equations of state of the plasma are described by a real gas approximation, which divides the internal energy into the thermal energy of atoms, ions and electrons, ionization energy and the excitation energy of atoms and ions. The dynamic evolution of the silicon target and plasma during laser ablation is studied by using this model, and the distributions of the temperature, plasma density, Mach number related to the evaporation/condensation of the target surface, laser transmissivity as well as internal energy of the plasma are given. It is found that the evolution of the target surface during laser ablation can be divided into three stages: (1) the target surface temperature increases continuously;(2) the sonic and subsonic evaporation; and (3) the subsonic condensation. The result of the internal energy distribution indicates that the ionization and excitation energy plays an important role in the internal energy of the plasma during laser ablation. This model is suitable for the case that the temperature of the target surface is lower than the critical temperature.

Two-dimensional axisymmetric radiation hydrodynamics model of moderate-intensity nanosecond laser-produced plasmas

“…Other models [18,19,24] adopted a more simplified ideal gas approximation, that is, only the contribution of thermal energy was included. However, the numerical simulation study of Shabanov Gornushkin [31] and our previous work [32] show that the above simplified treatments of internal energy are not always effective in LPP. Actually, the contribution of excitation energy to internal energy is very important in the early stage of hot plasma evolution, which corresponds to the importance of radiative process in this stage [31].…”

“…The solution of heat conduction equation (1) also requires the following four boundary conditions and an initial condition [32]…”

Micro-impulse and plasma plume produced by irradiating aluminum target with nanosecond laser pulses in double-pulse scheme

“…Laser ablation propulsion (LAP) uses the recoil force caused by laser ablation for noncontact manipulation in space [1]. When an intense laser pulse irradiates the target, the surface material of the target melts, evaporates and even generates a plasma plume [2,3]. Then the plasma plume, with high temperature and pressure, expands away from the target surface at high speed.…”