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Aragón Garbizu, Carlos

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https://academica-e.unavarra.es/handle/2454/48553

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Aragón Garbizu

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Carlos

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InaMat2. Instituto de Investigación en Materiales Avanzados y Matemáticas

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0000-0003-1737-6402

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2014 - 201922020 - 20241
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Author: Aragón Garbizu, Carlos × Subject: LIBS ×

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Now showing 1 - 3 of 3
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    PublicationOpen Access
    CSigma graphs: a new approach for plasma characterization in laser-induced breakdown spectroscopy
    (Elsevier, 2014) Aragón Garbizu, Carlos; Aguilera Andoaga, José Antonio; Física; Fisika
    A generalization of curves of growth called CSigma (Cσ) graphs, which allows including several lines of various elements in the same ionization state at different concentrations, is proposed for laser-induced breakdown spectroscopy (LIBS) experiments. The method relies on the Boltzmann, Saha and radiative transfer equations for plasmas in local thermodynamic equilibrium. Cσ graphs are based on the calculation of a line cross section σl for each of the experimental data, starting from the atomic data of the line, the temperature and the electron density. A model of homogeneous plasma, applied separately for neutral atoms and ions, is used. A limit of validity is established for this model. Experimental Cσ graphs have been obtained using fused glass samples containing Fe, Mn, Mg, Si and Cr. By fitting experimental Cσ graphs to calculated curves, the LIBS system becomes characterized by a set of four parameters βA, Nl, T, Ne, different for neutral atoms and ions. Starting from this characterization, the intensity and self-absorption of a given spectral line of an element at a certain concentration may be predicted, provided that its atomic data are known and the limit of validity is not exceeded.
  • Thumbnail Image
    PublicationOpen Access
    Direct analysis of aluminum alloys by CSigma laser-induced breakdown spectroscopy
    (Elsevier, 2018) Aragón Garbizu, Carlos; Aguilera Andoaga, José Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
    We report the application of CSigma laser-induced breakdown spectroscopy (Cσ-LIBS) to quantitative analysis of aluminum alloys without sample preparation. Cσ-LIBS simplifies strongly the conventional calibration procedure of LIBS, replacing it with a characterization stage performed from the spectrum of a single standard sample. The aim of this work has been to provide a complete evaluation of the use of Cσ-LIBS for direct analysis by obtaining its figures of merit, including precision and limits of detection. Ten elements (Si, Fe, Cu, Mn, Mg, Cr, Ni, Zn, Ti and Ca) are determined in a set of six certified samples with a wide range of concentrations, from percent down to μg/g levels. The average precision is 8.0% for concentrations higher than 0.1 wt% and 13% for concentrations between 0.1 wt% and 0.01 wt%. The limits of detection are in the range 1.4–9.7 μg/g.
  • Thumbnail Image
    PublicationOpen Access
    New procedure for CSigma laser induced breakdown spectroscopy addressing the laser-induced plasma inhomogeneity
    (Elsevier, 2024-06-06) Aguilera Andoaga, José Antonio; Aragón Garbizu, Carlos; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
    CSigma laser-induced breakdown spectroscopy (Cσ-LIBS), as the other methods for quantitative elemental analysis by LIBS based on plasma characterization, is negatively affected by the inhomogeneity of laser-induced plasmas. In the present work, we propose a new procedure for Cσ-LIBS which addresses the plasma inhomogeneity problem. The key features of the method are: (1) the extension of the concept of apparent temperature to other plasma parameters (apparent plasma) and its use in both the ionization and excitation equilibria and (2) the addition to the theoretical Cσ curve of a linear contribution arising from the plasma regions of low optical depth. In ionization equilibrium, the inhomogeneity requires separated Cσ graphs and different apparent ionization temperatures for neutral atom and ion emissions. In excitation equilibrium, we account for the inhomogeneity by obtaining a different apparent temperature for each multiplet included in the Cσ graph. In this way, the procedure only requires the fitting of a limited number of parameters to describe the inhomogeneous plasma, as the multiplet temperatures Ti are determined by a straightforward iteration procedure of fast convergence. The improved treatment of plasma inhomogeneity allows to include intense resonance lines in Cσ graphs, which were previously avoided. The development of the method has demanded accurate experimental Cσ graphs, obtained with seven certified aluminum alloys. The laser-induced plasma is generated in air at atmospheric pressure, the most common and versatile ambient gas condition for LIBS, which is known to produce a strongly inhomogeneous plasma. To validate the analytical application of the method, the samples are divided into three characterization samples and four analytical samples. The average deviation of the determined concentrations from the certified values has been 8.5% for elements with concentrations greater than 0.05 wt%.