Laser Ablation of Aluminum Near the Critical Regime: A Computational Gas-Dynamical Model with Temperature-Dependent Physical Parameters

Jacopo Terragni,Antonio Miotello

doi:10.3390/mi12030300

Abstract

The complexity of the phenomena simultaneously occurring, from the very first instants of high-power laser pulse interaction with the target up to the phase explosion, along with the strong changes in chemical-physical properties of matter, makes modeling laser ablation a hard task, especially near the thermodynamic critical regime. In this work, we report a computational model of an aluminum target irradiated in vacuum by a gaussian-shaped pulse of 20 duration, with a peak intensity of the order of . This continuum model covers laser energy deposition and temperature evolution in the irradiated target, along with the mass removal mechanism involved, and the vaporized material expansion. Aluminum was considered to be a case study due to the vast literature on the temperature dependence of its thermodynamic, optical, and transport properties that were used to estimate time-dependent values of surface-vapor quantities (vapor pressure, vapor density, vapor and surface temperature) and vapor gas-dynamical quantities (density, velocity, pressure) as it expands into vacuum. Very favorable agreement is reported with experimental data regarding: mass removal and crater depth due to vaporization, generated recoil momentum, and vapor flow velocity expansion.

Highlights

The application of the laser ablation (LA) technique covers a great variety of scientific and technological fields: Pulsed Laser Deposition (PLD) [1], nanoparticles production [2], Laser Induced Breakdown Spectroscopy (LIBS) for chemical analysis of solid materials [3], high-precision artwork restoration [4], investigation of the conditions for inertial confinement fusion [5]
In this work we focused on LA, in vacuum, of an aluminum target generated by a Gaussian-shaped laser pulse of 20 ns duration (FWHM)
We notice that higher the fluence, higher the maximum value of the surface temperature, since a larger amount of energy is released by the laser pulse and absorbed in the first layers of the target

Summary

Introduction

The application of the laser ablation (LA) technique covers a great variety of scientific and technological fields: Pulsed Laser Deposition (PLD) [1], nanoparticles production [2], Laser Induced Breakdown Spectroscopy (LIBS) for chemical analysis of solid materials [3], high-precision artwork restoration [4], investigation of the conditions for inertial confinement fusion [5]. Despite being so widely used, LA is far from being completely understood. Even if this technique can be summarized by the interaction of an intense laser pulse with a target and the consequent material emission, there is a wide variety of physical phenomena occurring in this process, which are strongly dependent on laser pulse features, target material composition, and ambient atmosphere. With a peak intensity of the order of GW/cm2 The choice of this target material naturally arises by considering that a consistent part of space debris is made of aluminum [8] and that aluminum is widely used in LAP, both as a propulsion performance standard [9]

Methods

Results

Conclusion