Mourad Djebli | Université des Sciences et Technologie Houari Boumediene (USTHB) (original) (raw)

Papers by Mourad Djebli

An impurity control scheme in plasmas [M. Amroun and R. Annou, Phys. Plasmas 8, 5331(2001)] where... more An impurity control scheme in plasmas [M. Amroun and R. Annou, Phys. Plasmas 8, 5331(2001)] where electrons ions and dust grains get separated when experiencing a cyclotron wave generated ponderomotive force, is numerically investigated. The electron and ion ponderomotive forces are included and the system of differential equations is solved. It is shown, that plasma-impurity separation is effective beyond a critical distance from the source.

The expansion of plasma plume produced by a laser ablation is investigated using the self-similar... more The expansion of plasma plume produced by a laser ablation is investigated using the self-similar approach. Based on the fluid model and the quasi-neutral assumption, the one dimensional expansion of an either vapor or partially ionized gas is studied for a collisionless plasma in the presence of electrons in thermal equilibrium. The uniqueness of the self-similar solution is questioned. Two different self-similar transformations for the ion density are proposed, one commonly used for free plasma expansion and the other corresponds to the expansion with diffusion. The density profiles and the self-similar parameter limit, corresponding to the end of the expansion, are found to be strongly affected by the transformation. A comparison is made with experimental results of a plasma produced by nanosecond laser pulse interacting with a metallic titanium target in a vacuum.

A one-fluid, one-dimensional magneto-hydrodynamic (MHD) model is used to investigate the dynamics... more A one-fluid, one-dimensional magneto-hydrodynamic (MHD) model is used to investigate the dynamics of magnetized laser produced plasma expanding into vacuum, just after the termination of the laser pulse. The created plasma plume is assumed to be fully ionized containing electrons and singly charged ions and considered to be under local thermodynamic equilibrium, allowing all charged particles to have same temperatures. A selfsimilar solution is found to describe the expansion of the plasma satisfying ideal time-dependant MHD equations where charge quasi-neutrality is assumed to prevail. The evolution of the transverse magnetic field is supposed to follow Faraday law and the set of obtained differential equations is closed with an ideal equation of state. The numerical results report the behaviour of the deduced plasma parameters like density, velocity and temperature as functions of the self-similarity variable for different increasing initial values of magnetic field. We find that the interaction of the plasma with the transverse magnetic field may cause significant changes in the plume expansion dynamics, including confinement of the plasma leading to the increase of particles arriving on the substrate. Velocity plasma increase is also observed due to the Lorentz force that accelerates the charges to move faster and further away from the target. The temperature of the plume is found to be larger compared to temperature in un-magnetized plasma, due to Joule heating and magnetic compression of the plume.

ABSTRACT The dynamics of a laser ablation plume during the first stage of its expansion, just aft... more ABSTRACT The dynamics of a laser ablation plume during the first stage of its expansion, just after the termination of the laser pulse is modeled. First, we suppose the laser fluence range low enough to consider a neutral vapor. The expansion of the evaporated material is described by one-component fluid and one-dimensional Euler equations. The vapor is assumed to follow an ideal gas flow. For high energetic ions, the charge separation can be neglected and the hydrodynamics equations can be solved using self-similar formulation. The obtained ordinary differential equations are solved numerically. Secondly, the effect of ionization is investigated when the evaporated gas temperature is sufficiently high. In this case, Saha equation is included in the formulation of the model. We find a self-similar solution for a finite value of the similarity variable which depends on the laser ablation parameters.

Numerical simulations based on the Monte Carlo method are conducted to investigate ground-state c... more Numerical simulations based on the Monte Carlo method are conducted to investigate ground-state configurations and phase transitions of strongly coupled dust particles. The interaction between negatively charged dust particles is modeled by three different potentials, namely, Coulomb, Yukawa, and logarithmic. The effect of random charge fluctuation is taken into account for a dominant charging process by particles collection and in the presence of two dimensional parabolic confinement potential. Structural arrangement and phase transition are found to be dependent on the potential interaction and the charge fluctuation. The changes in the melting temperature, when the charge fluctuation is taken into account, are particularly noticeable for systems with particles interacting through logarithmic potential.

The expansion of plasma created by laser ablation is investigated using the fluid model. At the f... more The expansion of plasma created by laser ablation is investigated using the fluid model. At the first stage of the expansion, electrons are considered in thermal equilibrium. The presence of highly charged impurities is considered through Poisson's equation. The set of nonlinear differential equations is solved using a moving boundary and taken into account the charge separation effect. The uniformly distributed impurities can accelerate or decelerate the ion motion depending on their charge and concentration. It is also found that the separation of the charge is valid for a specific time which depends on the impurities parameters.

An impurity control scheme in plasmas [M. Amroun and R. Annou, Phys. Plasmas 8, 5331(2001)] where... more An impurity control scheme in plasmas [M. Amroun and R. Annou, Phys. Plasmas 8, 5331(2001)] where electrons ions and dust grains get separated when experiencing a cyclotron wave generated ponderomotive force, is numerically investigated. The electron and ion ponderomotive forces are included and the system of differential equations is solved. It is shown, that plasma-impurity separation is effective beyond a critical distance from the source.

The expansion of plasma plume produced by a laser ablation is investigated using the self-similar... more The expansion of plasma plume produced by a laser ablation is investigated using the self-similar approach. Based on the fluid model and the quasi-neutral assumption, the one dimensional expansion of an either vapor or partially ionized gas is studied for a collisionless plasma in the presence of electrons in thermal equilibrium. The uniqueness of the self-similar solution is questioned. Two different self-similar transformations for the ion density are proposed, one commonly used for free plasma expansion and the other corresponds to the expansion with diffusion. The density profiles and the self-similar parameter limit, corresponding to the end of the expansion, are found to be strongly affected by the transformation. A comparison is made with experimental results of a plasma produced by nanosecond laser pulse interacting with a metallic titanium target in a vacuum.

A one-fluid, one-dimensional magneto-hydrodynamic (MHD) model is used to investigate the dynamics... more A one-fluid, one-dimensional magneto-hydrodynamic (MHD) model is used to investigate the dynamics of magnetized laser produced plasma expanding into vacuum, just after the termination of the laser pulse. The created plasma plume is assumed to be fully ionized containing electrons and singly charged ions and considered to be under local thermodynamic equilibrium, allowing all charged particles to have same temperatures. A selfsimilar solution is found to describe the expansion of the plasma satisfying ideal time-dependant MHD equations where charge quasi-neutrality is assumed to prevail. The evolution of the transverse magnetic field is supposed to follow Faraday law and the set of obtained differential equations is closed with an ideal equation of state. The numerical results report the behaviour of the deduced plasma parameters like density, velocity and temperature as functions of the self-similarity variable for different increasing initial values of magnetic field. We find that the interaction of the plasma with the transverse magnetic field may cause significant changes in the plume expansion dynamics, including confinement of the plasma leading to the increase of particles arriving on the substrate. Velocity plasma increase is also observed due to the Lorentz force that accelerates the charges to move faster and further away from the target. The temperature of the plume is found to be larger compared to temperature in un-magnetized plasma, due to Joule heating and magnetic compression of the plume.

ABSTRACT The dynamics of a laser ablation plume during the first stage of its expansion, just aft... more ABSTRACT The dynamics of a laser ablation plume during the first stage of its expansion, just after the termination of the laser pulse is modeled. First, we suppose the laser fluence range low enough to consider a neutral vapor. The expansion of the evaporated material is described by one-component fluid and one-dimensional Euler equations. The vapor is assumed to follow an ideal gas flow. For high energetic ions, the charge separation can be neglected and the hydrodynamics equations can be solved using self-similar formulation. The obtained ordinary differential equations are solved numerically. Secondly, the effect of ionization is investigated when the evaporated gas temperature is sufficiently high. In this case, Saha equation is included in the formulation of the model. We find a self-similar solution for a finite value of the similarity variable which depends on the laser ablation parameters.

Numerical simulations based on the Monte Carlo method are conducted to investigate ground-state c... more Numerical simulations based on the Monte Carlo method are conducted to investigate ground-state configurations and phase transitions of strongly coupled dust particles. The interaction between negatively charged dust particles is modeled by three different potentials, namely, Coulomb, Yukawa, and logarithmic. The effect of random charge fluctuation is taken into account for a dominant charging process by particles collection and in the presence of two dimensional parabolic confinement potential. Structural arrangement and phase transition are found to be dependent on the potential interaction and the charge fluctuation. The changes in the melting temperature, when the charge fluctuation is taken into account, are particularly noticeable for systems with particles interacting through logarithmic potential.

The expansion of plasma created by laser ablation is investigated using the fluid model. At the f... more The expansion of plasma created by laser ablation is investigated using the fluid model. At the first stage of the expansion, electrons are considered in thermal equilibrium. The presence of highly charged impurities is considered through Poisson's equation. The set of nonlinear differential equations is solved using a moving boundary and taken into account the charge separation effect. The uniformly distributed impurities can accelerate or decelerate the ion motion depending on their charge and concentration. It is also found that the separation of the charge is valid for a specific time which depends on the impurities parameters.