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Seyed Hassan Tavassoli - One of the best experts on this subject based on the ideXlab platform.

  • Effect of background gas pressure and laser pulse intensity on laser induced Plasma Radiation of copper samples
    Physics of Plasmas, 2010
    Co-Authors: S. Mehrabian, Maryam Aghaei, Seyed Hassan Tavassoli
    Abstract:

    Study of laser induced Plasma emission of Cu in one dimension is numerically carried out. Effects of different background gas pressure (He), 100, 500, and 760 torr, and laser pulse intensities, 0.5, 0.7, and 1 GW/cm2, on the Plasma emission as well as ablation processes are investigated. Under a specified condition, heat conduction equation in the target accompanied with gas dynamic equations in the plume is solved simultaneously. The mentioned equations are coupled to each other through the Knudsen layer conditions and the energy and mass balances at the interface between the target and the vapor. The Bremsstrahlung Radiation of Plasma and the spectral emission of copper atoms are studied under various background gas pressure and laser pulse intensities. Furthermore, number density of He, Cu, and the electron, pressure, and temperature of the plume under various conditions are obtained. In the early time after laser pulse, Plasma Radiation is mainly due to the Bremsstrahlung Radiation while after some 10...

  • simulation of nanosecond pulsed laser ablation of copper samples a focus on laser induced Plasma Radiation
    Journal of Applied Physics, 2008
    Co-Authors: Maryam Aghaei, S. Mehrabian, Seyed Hassan Tavassoli
    Abstract:

    A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha–Eggert equations are used to investigate Plasma formation. The shielding effect of the Plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody Radiation and spectral emissions of the Plasma are also investigated. Spatial and temporal distribution of the target temperature,number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody Radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody Radiation, and also Cuspectral emissions indicates that although in early times the bremsstrahlung Radiation dominates the two other Radiations, the Copperspectral emission is the dominant Radiation in later times. It should be mentioned that the blackbody Radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolvedspectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung Radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

S. Mehrabian - One of the best experts on this subject based on the ideXlab platform.

  • Effect of background gas pressure and laser pulse intensity on laser induced Plasma Radiation of copper samples
    Physics of Plasmas, 2010
    Co-Authors: S. Mehrabian, Maryam Aghaei, Seyed Hassan Tavassoli
    Abstract:

    Study of laser induced Plasma emission of Cu in one dimension is numerically carried out. Effects of different background gas pressure (He), 100, 500, and 760 torr, and laser pulse intensities, 0.5, 0.7, and 1 GW/cm2, on the Plasma emission as well as ablation processes are investigated. Under a specified condition, heat conduction equation in the target accompanied with gas dynamic equations in the plume is solved simultaneously. The mentioned equations are coupled to each other through the Knudsen layer conditions and the energy and mass balances at the interface between the target and the vapor. The Bremsstrahlung Radiation of Plasma and the spectral emission of copper atoms are studied under various background gas pressure and laser pulse intensities. Furthermore, number density of He, Cu, and the electron, pressure, and temperature of the plume under various conditions are obtained. In the early time after laser pulse, Plasma Radiation is mainly due to the Bremsstrahlung Radiation while after some 10...

  • simulation of nanosecond pulsed laser ablation of copper samples a focus on laser induced Plasma Radiation
    Journal of Applied Physics, 2008
    Co-Authors: Maryam Aghaei, S. Mehrabian, Seyed Hassan Tavassoli
    Abstract:

    A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha–Eggert equations are used to investigate Plasma formation. The shielding effect of the Plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody Radiation and spectral emissions of the Plasma are also investigated. Spatial and temporal distribution of the target temperature,number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody Radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody Radiation, and also Cuspectral emissions indicates that although in early times the bremsstrahlung Radiation dominates the two other Radiations, the Copperspectral emission is the dominant Radiation in later times. It should be mentioned that the blackbody Radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolvedspectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung Radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

S De Benedictis - One of the best experts on this subject based on the ideXlab platform.

  • laser triggered single streamer in a pin to pin coplanar dielectric barrier discharge
    Applied Physics Letters, 2009
    Co-Authors: P F Ambrico, M Ambrico, Milan Simek, A Colaianni, G Dilecce, S De Benedictis
    Abstract:

    The effect of laser light interaction with alumina surface of a single filament coplanar dielectric barrier discharge has been investigated. It has been found that for laser photon energy lower than the pure alumina photoelectron emission threshold, the laser beam was effective in triggering single streamer discharge below regular ignition voltage threshold. This work demonstrates that triggering of the filamentary discharge occurs due to the laser induced extraction of electrons originally trapped by the Plasma Radiation at the dielectric surface; the trap energy levels lower than the dielectric band gap explain the easier electron detrapping due to incident laser photons.

Maryam Aghaei - One of the best experts on this subject based on the ideXlab platform.

  • Effect of background gas pressure and laser pulse intensity on laser induced Plasma Radiation of copper samples
    Physics of Plasmas, 2010
    Co-Authors: S. Mehrabian, Maryam Aghaei, Seyed Hassan Tavassoli
    Abstract:

    Study of laser induced Plasma emission of Cu in one dimension is numerically carried out. Effects of different background gas pressure (He), 100, 500, and 760 torr, and laser pulse intensities, 0.5, 0.7, and 1 GW/cm2, on the Plasma emission as well as ablation processes are investigated. Under a specified condition, heat conduction equation in the target accompanied with gas dynamic equations in the plume is solved simultaneously. The mentioned equations are coupled to each other through the Knudsen layer conditions and the energy and mass balances at the interface between the target and the vapor. The Bremsstrahlung Radiation of Plasma and the spectral emission of copper atoms are studied under various background gas pressure and laser pulse intensities. Furthermore, number density of He, Cu, and the electron, pressure, and temperature of the plume under various conditions are obtained. In the early time after laser pulse, Plasma Radiation is mainly due to the Bremsstrahlung Radiation while after some 10...

  • simulation of nanosecond pulsed laser ablation of copper samples a focus on laser induced Plasma Radiation
    Journal of Applied Physics, 2008
    Co-Authors: Maryam Aghaei, S. Mehrabian, Seyed Hassan Tavassoli
    Abstract:

    A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha–Eggert equations are used to investigate Plasma formation. The shielding effect of the Plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody Radiation and spectral emissions of the Plasma are also investigated. Spatial and temporal distribution of the target temperature,number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody Radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody Radiation, and also Cuspectral emissions indicates that although in early times the bremsstrahlung Radiation dominates the two other Radiations, the Copperspectral emission is the dominant Radiation in later times. It should be mentioned that the blackbody Radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolvedspectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung Radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

Le B Drogoff - One of the best experts on this subject based on the ideXlab platform.

  • influence of the laser pulse duration on laser produced Plasma properties
    Plasma Sources Science and Technology, 2004
    Co-Authors: Le B Drogoff, Jonas Margot, S Laville, Mohamad Sabsabi, Francois Vidal, T W Johnston, Mustapha Chaker, O Barthelemy
    Abstract:

    In the framework of laser-induced Plasma spectroscopy (LIPS) applications, time-resolved characteristics of laser-produced aluminium Plasmas in air at atmospheric pressure are investigated for laser pulse durations ranging from 100 fs to 270 ps. Measurements show that for delays after the laser pulse longer than ~100 ns, the Plasma temperature increases slightly with the laser pulse duration, while the electron density is independent of it. In addition, as the pulse duration increases, the Plasma Radiation emission lasts longer and the spectral lines arise later from the continuum emission. The time dependence of the continuum emission appears to be similar whatever the duration of the laser pulse is, while the temporal evolution of the line emission seems to be affected mainly by the Plasma temperature. Finally, as far as spectrochemical applications (such as LIPS) of laser-produced Plasmas are concerned, this study highlights the importance of the choice of appropriate temporal gating parameters for each laser pulse duration.