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Proceedings ArticleDOI

Laser induced breakdown spectroscopy analysis of lunar simulants under high vacuum conditions

01 Nov 2010-pp 449-453

Abstract: Application of laser induced breakdown spectroscopy (LIBS) is considered for compositional analysis of materials on planetary surfaces. In many such applications, LIBS measurements are conducted in high vacuum and the propagation of the plume produced during laser ablation plays a significant role. Therefore a proper understanding of the plasma parameters under high vacuum is significant for any improvement in the LIBS system. In this study, hydrodynamic equations are used to model plasma dynamics. A model is used to understand laser assisted ablation and plume dynamics under high vacuum condition. Further, experimental studies are performed to analyze the lunar simulant soil. Experimentally observed lunar simulant plasma temperature was comparable with the theoretically estimated Si plasma temperature. This shows that plasma characteristic of lunar soil is mainly influenced by silicon which is the major constituent element present. The emission life time of silicon and lunar simulant are measured under different ambient pressure conditions. The measured life time is very short in vacuum as compared to that of at an atmospheric pressure. This is due to the high velocity and fast expansion of the plume under high vacuum (5×10−9 bar) condition.
Topics: Laser-induced breakdown spectroscopy (60%), Laser ablation (56%), Ultra-high vacuum (55%), Lunar soil (53%), Plasma parameters (52%)
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Journal ArticleDOI
Abstract: The paper is built up in two parts. First, a rather comprehensive introduction is given, with a brief overview of the different application fields of laser ablation, focusing mainly on the analytical applications, and an overview of the different modeling approaches available for laser ablation. Further, a discussion is presented here about the laser evaporated plume expansion in vacuum or in a background gas, as well as about the different mechanisms for particle formation in the laser ablation process, which is most relevant for laser ablation as solid sampling technique for inductively coupled plasma (ICP) spectrometry. In the second part, a model is presented that describes the interaction of an ns-pulsed laser with a Cu target, as well as the resulting plume expansion and plasma formation. The results presented here, include the temperature distribution in the target, the melting and evaporation of the target, the vapor density, velocity and temperature distribution in the evaporated plume, the ionization degree and the density profiles of Cu atoms, Cu and Cu ions and electrons in the plume (plasma), as well as the resulting plasma shielding of 0 q 2q the incoming laser beam. Results are presented as a function of time during and after the laser pulse, and as a function of position in the target or in the plume. The influence of the target reflection coefficient on the above calculation results is investigated. Finally, the effect of the laser pulse fluence on the target heating, melting and vaporization, and on the plume characteristics and plasma formation is studied. Our modeling results are in reasonable agreement with calculated and measured data from literature. 2003 Elsevier B.V. All rights reserved.

399 citations


"Laser induced breakdown spectroscop..." refers background or methods or result in this paper

  • ...The obtained temperature profile is well in agreement with literature [5]....

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  • ...For metals, absorption coefficient is generally of the order of 10 7 m −1 [5], and thus the absorption length is in nano-meter order....

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  • ...Different modeling approaches are available and can be categorized as: i) approach based on hydrodynamic continuity equations, ii) approach based on Monte-Carlo Simulations [4], iii) approach based on analytical expressions derived from the hydrodynamic continuity equations [5,6]....

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Journal ArticleDOI
12 Dec 2002-Physical Review E
TL;DR: A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas and it is shown that the calculations suggest localized formation of molecules during reactive laser ablation.
Abstract: The physical phenomena involved in the interaction of a laser-generated plasma plume with a background gas are studied numerically. A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas. The proposed approach takes advantages of both continuous and microscopic descriptions. The simulation technique is suitable for the simulation of high-rate laser ablation for a wide range of background pressure. The model takes into account the mass diffusion and the energy exchange between the ablated and background species, as well as the collective motion of the ablated species and the background-gas particles. The developed approach is used to investigate the influence of the background gas on the expansion dynamics of the plume obtained during the laser ablation of aluminum. At moderate pressures, both plume and gas compressions are weak and the process is mainly governed by the diffusive mixing. At higher pressures, the interaction is determined by the plume-gas pressure interplay, the plume front is strongly compressed, and its center exhibits oscillations. In this case, the snowplough effect takes place, leading to the formation of a compressed gas layer in front of the plume. The background pressure needed for the beginning of the snowplough effect is determined from the plume and gas density profiles obtained at various pressures. Simulation results are compared with experimentally measured density distributions. It is shown that the calculations suggest localized formation of molecules during reactive laser ablation.

182 citations


"Laser induced breakdown spectroscop..." refers methods in this paper

  • ...Different modeling approaches are available and can be categorized as: i) approach based on hydrodynamic continuity equations, ii) approach based on Monte-Carlo Simulations [4], iii) approach based on analytical expressions derived from the hydrodynamic continuity equations [5,6]....

    [...]


Journal ArticleDOI
Abstract: Laser-induced Breakdown Spectroscopy (LIBS) is actively under development for future use on surface probes to Mars. The analytical method can be deployed for in-situ and/or stand-off analysis with the latter embodiment providing the greatest advantages compared to previous and current elemental analysis methods used for planetary surface analysis. For this application, LIBS must be thoroughly investigated in terms of analytical capabilities and flight-rated instruments must be developed. Because of the low pressure of the predominantly CO2 atmosphere on Mars, studies are needed to understand analytical requirements and to determine performance under these conditions. Stand-off analysis demands the most stringent requirements on instrumentation. Therefore, it must be determined if the high performance components that are normally used in a typical LIBS laboratory setup, which are generally not optimized for small size and weight, are essential to obtain the maximum scientific return from a mission. A key component of a LIBS apparatus is the detection system consisting of a spectrograph and a detector. Here we present an evaluation of one design of a compact spectrograph (Ocean Optics HR2000) for in-situ and stand-off LIBS analyses of geological samples under Mars atmospheric conditions.

121 citations


"Laser induced breakdown spectroscop..." refers background in this paper

  • ...LIBS tools will be an important payload in most of the forthcoming space exploration missions [1]....

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Journal ArticleDOI
Abstract: Plasma created during electrical discharge machining is systematically investigated using optical emission spectroscopy. Typical spectra show a strong H-alpha and continuum radiation, with many lines emitted by impurities coming from electrode and workpiece materials. The dielectric molecules are cracked by the discharge. Changing polarity affects the electrode wear and workpiece erosion rates, which can be qualitatively seen on the spectra. Time-resolved spectroscopy shows that the plasma density reaches 2 x 10(18) cm(-3) at the beginning of the discharge. This extreme density causes the merging of lines, strong Stark broadening and shift of the H-alpha line. Afterwards, the density decreases rapidly with time. The electron temperature remains roughly constant around 0.7 eV. The low temperature and the high density measured prove that the EDM plasma is non-ideal (Gamma similar or equal to 0.45). Absence of the H-beta line, asymmetric shape of the H-alpha line and complex structures around H-alpha are other spectroscopic evidences of the plasma non-ideality.

65 citations


Journal ArticleDOI
Ashwini Kumar Sharma1, Raj K. Thareja1Institutions (1)
Abstract: We report on the plume dynamics of pulsed laser ablated aluminum in ambient nitrogen pressure varying from 001 to 70 Torr using ICCD images of the expanding plasma plume At pressures of 001 to 1 Torr plasma expansion followed shock model whereas at 10 and 70 Torr plasma expansion followed drag model The difference in the values of vapor and shock temperatures calculated at 01 and 70 Torr has been used to understand the formation of AlN in vapor phase At pressures ≥ 1 Torr and later times plasma–gas interface showed instability in the leading edge of the expanding plume attributed to Rayleigh–Taylor instability

61 citations


"Laser induced breakdown spectroscop..." refers background in this paper

  • ...Many research groups have performed experiments [2,3] and numerical simulations on LIBS, but the complete mechanism of laser-target material interaction and subsequent plasma dynamics is not fully understood....

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