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Scotti U Di Uccio - One of the best experts on this subject based on the ideXlab platform.

  • pulsed laser deposition of srtio3 lagao3 and srtio3 laalo3 Plasma Plume effects
    Applied Physics Letters, 2010
    Co-Authors: C Aruta, S Amoruso, R Bruzzese, X Wang, Davide Maccariello, Miletto F Granozio, Scotti U Di Uccio
    Abstract:

    The pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3 interfaces is analyzed with a focus on the kinetic energy of the ablated species. LaGaO3 and LaAlO3 Plasma Plumes were studied by fast photography and space-resolved optical emission spectroscopy. Reflection high energy electron diffraction was performed proving a layer-by-layer growth up to 10−1 mbar oxygen pressure. The role of the energetic Plasma Plume on the two-dimensional growth and on the presence of interfacial defects at different oxygen growth pressures is discussed in connection with the conducting properties of the polar/nonpolar interfaces.

  • pulsed laser deposition of srtio3 lagao3 and srtio3 laalo3 Plasma Plume effects
    arXiv: Materials Science, 2010
    Co-Authors: C Aruta, S Amoruso, R Bruzzese, X Wang, Davide Maccariello, Miletto F Granozio, Scotti U Di Uccio
    Abstract:

    Pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3 interfaces has been analyzed with a focus on the kinetic energy of the ablated species. LaGaO3 and LaAlO3 Plasma Plumes were studied by fast photography and space-resolved optical emission spectroscopy. Reflection high energy electron diffraction was performed proving a layer-by-layer growth up to 10-1 mbar oxygen pressure. The role of the energetic Plasma Plume on the two-dimensional growth and the presence of interfacial defects at different oxygen growth pressure has been discussed in view of the conducting properties developing at such polar/non-polar interfaces.

Zygmunt Szymanski - One of the best experts on this subject based on the ideXlab platform.

  • Plasma Plume induced during ArF laser ablation of hydroxyapatite
    Applied Surface Science, 2008
    Co-Authors: M. Jedyński, J. Hoffman, Waldemar Mróz, Zygmunt Szymanski
    Abstract:

    Abstract Plasma Plume induced by ArF excimer laser ablation of a hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) target was studied during expansion into a vacuum or water vapour. The ArF laser operated at a wavelength of 193 nm with a pulse energy of 300–350 mJ and a 20 ns pulse duration. The emission spectra of the Plasma Plume were registered with the use of a spectrograph and an ICCD camera. The expansion of the Plasma Plume was studied using the time of flight method. The time-dependent radiation of the Ca I and Ca II lines was registered with the use of a monochromator and photomultiplier at various distances from the target. The dynamics of the Plasma Plume was also imaged by means of fast photography. It was found that during expansion into a vacuum, the Plasma front moved with a constant velocity of 1.75 × 10 4  m s −1 , while in the case of ambient water vapour at a pressure of 20 Pa, velocities of 1.75 × 10 4 –1.5 × 10 3  m s −1 were found depending on the distance from the target. Electron densities of 1.2 × 10 24 –4.5 × 10 21  m −3 were determined from the Stark broadening of the Ca II and Ca I lines at distances of 1–25 mm from the target. Temperatures of 11,500–4500 K were determined from the relative intensities of carbon lines and continuum radiation at distances of 4–29 mm from the target. The results allowed the estimation of thermal and kinetic energies of ablated particles. During expansion into a vacuum, the kinetic energies of Ca, P and O atoms were 64, 49 and 25 eV, respectively. During expansion into water vapour, kinetic energies dropped to 0.47, 0.36 and 0.19 eV, respectively at a distance of 25 mm from the target and were comparable to the energies of thermal motion.

  • modelling of Plasma Plume induced during laser welding
    Journal of Physics D, 2006
    Co-Authors: Tomasz Mościcki, J. Hoffman, Zygmunt Szymanski
    Abstract:

    A theoretical modelling of the Plasma Plume induced during welding of iron sheets with CO2 laser is presented. The set of equations consists of the equations of conservation of mass, energy, momentum and the diffusion equation and is solved with the use of the commercially available program Fluent 6.1. The computations are made for a laser power of 1700?W and for two shielding gases?argon and helium. The results show a significant difference between these two cases. When helium is used as the shielding gas, the Plasma is much smaller and burns only where the metal vapour is slightly diluted by helium. In the case when argon is the shielding gas, there are actually two Plasmas: argon Plasma and metal Plasma. The flowfield shows that the velocity increases in the hot region but only part of the mass flux enters the Plasma core. In the case when argon is used as the shielding gas, the total absorption of the laser radiation amounts to 18?33% of the laser power depending on argon and iron vapour velocities. In the case of helium the total absorption is much lower and amounts to ~5% of the laser power.

  • Plasma Plume Induced During Laser Welding of Magnesium Alloys
    AIP Conference Proceedings, 2006
    Co-Authors: J. Hoffman, Zygmunt Szymanski, V. Azharonok
    Abstract:

    The Plasma produced during laser welding of magnesium alloy is studied. The space‐averaged electron densities are determined from the Stark broadening of the 4481.16 A Mg II spectral line. Their values reach 1.6×1023 m−3 near the metal surface. The intensities of the measured atomic 5528.41 A Mg I spectral line and 4481.16 A Mg II spectral line depend on the Plasma temperature and their profiles vary with the temperature and electron density. This fact was used to reproduce the radial temperature distribution in the Plasma Plume. The shape of the temperature distribution was assumed according to numerical calculations of Plasma Plume and exact values were found fitting the synthetic line profile to the experimental one. It has been found that the maximum Plasma temperature is 8000 K.

  • time dependent spectroscopy of Plasma Plume under laser welding conditions
    Journal of Physics D, 2004
    Co-Authors: J. Hoffman, Zygmunt Szymanski
    Abstract:

    Momentary emission spectra of iron and argon lines were measured in a Plasma Plume induced during welding with a continuous wave CO2 laser. Time-dependent spectra were registered using a fast gate, lens coupled microchannel plate image intensifier placed between a spectrograph and a 1254 silicon intensified target detector connected to an optical multichannel analyser. The results, together with the analysis of the colour images from a fast camera, show that in the case when argon is the shielding gas, two Plasmas exist: the argon Plasma and the iron Plasma. It has been found that during strong bursts the Plasma Plume over the keyhole consists mainly of metal vapour, not being diluted by the shielding gas. No apparent mixing of the metal vapour and the shielding gas has been observed. The space-averaged electron densities determined from the Stark broadening of the 7503.87, 7514.65 A Ar I lines amounts to (0.75–1.05) × 1023 m−3 depending on the distance from the surface. Assuming that argon is not mixed with the metal vapour and is in local thermodynamic equilibrium these electron densities correspond to the temperatures of 12–13 kK. At the peaks of strong vapour bursts the space-averaged electron densities determined from the Stark broadening of the 5383.37 A Fe I line are (0.6–1) × 1023 m−3. Numerical simulations showed that the maximum densities in the Plasma centre are considerably higher and amount to ~1.8 × 1023 m−3 and ~2.45 × 1023 m−3 in the case of the argon and metal Plasma, respectively. Consequently the absorption of the laser beam in the Plasma Plume amounts to ~5% of the beam power in the case of argon and 10% in the case of metal Plasma.

  • Spectroscopic measurements of Plasma Plume induced during the laser deposition of the hydroxyapatite
    Czechoslovak Journal of Physics, 2004
    Co-Authors: M. Jedyński, Zygmunt Szymanski, Waldemar Mróz, Artur Prokopiuk, Miroslav Jelinek, Tomáš Kocourek
    Abstract:

    Plasma Plume induced by ArF exeimer laser ablation of a Ca10(PO4)6(OH)2 hydroxyapatite target during deposition process has been studied in different ambient conditions, i.e. in air or water vapour. ArF laser operated at the wavelength of 193 nm with the pulse energy of 300 mJ and 20 ns pulse duration. Spectroscopic measurements of the emission spectra of Plasma Plume have been made with the use of a fast gate, lens coupled micro-channel plate (MCP) image intensifier placed between a spectrograph and a 1254 silicon intensified target (SIT) detector connected to an optical multichannel analyser. The electron densities of 1022 ÷ 1023m−3 have been determined from the Stark broadening of Ca I lines as a function of the distance from the target. The expansion of the Plasma Plume has been studied using the time of flight method. The time-dependent radiation of the 422.673 nm Ca I and 393.366 nm Ca II lines has been, registered with the use of a monochromator and photomultiplier at various distances from the target. Velocities between 104 ÷ 103 m/s have been found. The velocity in air is several times higher than in the case with water vapour. The Plasma Plume dynamics is also different in both cases. In the presence of water vapour the spliting of the Plasma Plume appears.

C Aruta - One of the best experts on this subject based on the ideXlab platform.

  • pulsed laser deposition of srtio3 lagao3 and srtio3 laalo3 Plasma Plume effects
    Applied Physics Letters, 2010
    Co-Authors: C Aruta, S Amoruso, R Bruzzese, X Wang, Davide Maccariello, Miletto F Granozio, Scotti U Di Uccio
    Abstract:

    The pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3 interfaces is analyzed with a focus on the kinetic energy of the ablated species. LaGaO3 and LaAlO3 Plasma Plumes were studied by fast photography and space-resolved optical emission spectroscopy. Reflection high energy electron diffraction was performed proving a layer-by-layer growth up to 10−1 mbar oxygen pressure. The role of the energetic Plasma Plume on the two-dimensional growth and on the presence of interfacial defects at different oxygen growth pressures is discussed in connection with the conducting properties of the polar/nonpolar interfaces.

  • pulsed laser deposition of srtio3 lagao3 and srtio3 laalo3 Plasma Plume effects
    arXiv: Materials Science, 2010
    Co-Authors: C Aruta, S Amoruso, R Bruzzese, X Wang, Davide Maccariello, Miletto F Granozio, Scotti U Di Uccio
    Abstract:

    Pulsed laser deposition of SrTiO3/LaGaO3 and SrTiO3/LaAlO3 interfaces has been analyzed with a focus on the kinetic energy of the ablated species. LaGaO3 and LaAlO3 Plasma Plumes were studied by fast photography and space-resolved optical emission spectroscopy. Reflection high energy electron diffraction was performed proving a layer-by-layer growth up to 10-1 mbar oxygen pressure. The role of the energetic Plasma Plume on the two-dimensional growth and the presence of interfacial defects at different oxygen growth pressure has been discussed in view of the conducting properties developing at such polar/non-polar interfaces.

Haichao Cui - One of the best experts on this subject based on the ideXlab platform.

  • spatial distribution characteristics of Plasma Plume on attenuation of laser radiation under subatmospheric pressure
    Applied Optics, 2015
    Co-Authors: Yan Luo, Xinhua Tang, Qintao Chen, Haichao Cui
    Abstract:

    The attenuation of a laser by Plasma Plume can be restrained for laser welding under subatmospheric pressure. Based on the experimental obtained spectra, the extinctions of a probe laser under different subatmospheric pressures and the spatial distribution of probe laser extinction were measured. The role of subatmospheric pressure on Plasma Plume was analyzed. The results show that, with decreasing ambient pressure, the extinction of a probe laser decreases, and the welding penetration depth increases. The maximum attainable value of extinction gets far away from the keyhole in the transversal and vertical directions. The attenuation of a fiber laser is about 10% under normal atmosphere, and it reaches only about 1% when the ambient pressure is reduced to 3 kPa.

  • Effect of subatmospheric pressure on Plasma Plume in fiber laser welding
    Journal of Materials Processing Technology, 2015
    Co-Authors: Yan Luo, Xinhua Tang, Qintao Chen, Haichao Cui
    Abstract:

    Abstract Laser welding under subatmospheric pressure was implemented, and the characteristics of weld bead were analyzed in terms of its penetration depth, width and heap height. Based on the analysis of behaviors of Plasma Plume captured by a high-speed camera, the attenuation effect was evaluated for different subatmospheric pressures. In order to understand the extinction of fiber laser, a probe laser was placed passing through Plasma Plume. And its extinction was obtained by solving Rayleigh approximation equation. In the given condition, while the ambient pressure was reduced to 3 kPa, the welding penetration depth became approximately two times deeper than that in normal atmosphere. To better illustrate the effect of subatmospheric pressure, the Plasma Plume was assumed to consist of diffusive, condensed and residual Plasma Plume. And the residual one plays dominant role in the extinction of fiber laser. When the ambient pressure dropped from 101 kPa to 3 kPa, the decent trend of extinction became more obvious.

  • Study on the effect of laser-induced Plasma Plume on penetration in fiber laser welding under subatmospheric pressure
    The International Journal of Advanced Manufacturing Technology, 2014
    Co-Authors: Qintao Chen, Yan Luo, Xinhua Tang, Haichao Cui
    Abstract:

    Under subatmospheric pressure, the influence of a Plasma Plume on weld penetration depth could be greatly improved in high-power laser welding. In this paper, a series of laser welding tests under different subatmospheric pressures were performed in a vacuum chamber. The dynamic images of the Plasma Plume were captured by a high-speed camera and analyzed. Based on the information extracted from the images, the variation of the Plasma Plume in gray level and spatial size were measured. For the whole Plasma Plume, the internal part plays a key role in the interaction with laser. So, the variation of brightness and size of the internal part were adopted as the characteristic parameters in describing the attenuation effect of laser caused by the Plasma Plume. Besides, a threshold value of pressure Pcr, which is critical to the dramatic change of penetration, was found in the range of 10 to 20 kPa. As the ambient pressure was decreased to this critical range, the Plasma Plume was drastically shrunk, leading to a great reduction of absorption and refraction effect on laser and a resultant sharp increase of weld penetration.

Michael G Kong - One of the best experts on this subject based on the ideXlab platform.

  • the mechanism of Plasma Plume termination for pulse excited Plasmas in a quartz tube
    Applied Physics Letters, 2017
    Co-Authors: Mingzhe Rong, Wenjie Xia, Xiaohua Wang, Zhijie Liu, Dingxin Liu, Zhihu Liang, Xiaoning Zhang, Michael G Kong
    Abstract:

    Although the formation and propagation of Plasma Plume for atmospheric pressure Plasmas have been intensively studied, how does the Plasma Plume terminate is still little known. In this letter, helium Plasma Plumes are generated in a long quartz tube by pulsed voltages and a constant gas flow. The voltages have a variable pulse width (PW) from 0.5 μs to 200 μs. It is found that the Plasma Plume terminates right after the falling edge of each voltage pulse when PW < 20 μs, whereas it terminates before the falling edge. When PW is larger than 30 μs, the duration of Plasma Plume starts to decrease, and the termination is found to occur at the current zero moment of the discharge current through the high-voltage electrode, which is much different from that through the ground electrode. This indicates that part of the discharge current is shunted by the Plasma Plume to its downstream gas region. An equivalent circuit model is developed, from which the surface charge deposited on the quartz tube is found crucia...

  • The Mechanism of Plasma Plume Termination for Pulse Excited Plasmas in a Quartz Tube
    Applied Physics Letters, 2017
    Co-Authors: Mingzhe Rong, Wenjie Xia, Xiaohua Wang, Zhijie Liu, Dingxin Liu, Zhihu Liang, Xiaoning Zhang, Michael G Kong
    Abstract:

    Although the formation and propagation of Plasma Plume for atmospheric pressure Plasmas have been intensively studied, how does the Plasma Plume terminate is still little known. In this letter, helium Plasma Plumes are generated in a long quartz tube by pulsed voltages and a constant gas flow. The voltages have a variable pulse width (PW) from 0.5 μs to 200 μs. It is found that the Plasma Plume terminates right after the falling edge of each voltage pulse when PW