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15 Dec 2009

Volume 106, Issue 12, Articles (12xxxx)

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Stopping power of a buffer gas for laser plasma debris mitigation

Davide Bleiner and Thomas Lippert

J. Appl. Phys. 106, 123301 (2009); http://dx.doi.org/10.1063/1.3271142 (5 pages) | Cited 3 times

Online Publication Date: 18 December 2009

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The stopping power of a buffer gas against laser-plasma debris is quantitatively assessed by means of visualization techniques. For ablation of planar tin targets in an Ar ambient, an expanding wavefront was visualized, whose translation energy was rapidly reduced within a few millimeters above the target surface. The fastest debris component was along the normal to the target with an initial kinetic energy of 1.1 keV. The buffer gas efficiency changed in a line-of-sight-dependent way, thermalizing more efficiently the on-axis components. The maximum stopping power of the gas buffer was determined as high as 0.4 keV/mm. Due to the reduction in stopping power, nonlinearly with the debris kinetic energy, a gas buffer thickness of 10 mm is required at the studied atmospheric pressure in order to mitigate high energy debris below a fiducial threshold of 0.1 keV.
Show PACS
52.38.Mf Laser ablation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
79.20.Eb Laser ablation

Heuristic modeling of spectral plasma emission for laser-induced breakdown spectroscopy

Rolf Wester and Reinhard Noll

J. Appl. Phys. 106, 123302 (2009); http://dx.doi.org/10.1063/1.3259402 (10 pages)

Online Publication Date: 30 December 2009

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A heuristic model was developed to describe the spectral emission of laser-induced plasmas generated for laser-induced breakdown spectroscopy under the assumption that the composition of the plasma and the plasma state is known. The plasma is described by a stationary spherical shell model surrounded by an ambient gas, which partially absorbs the emitted radiation. The radiation transport equation is used to calculate the spectrum emitted by the plasma. Simulations of a multiline iron spectrum and a self-reversed Al line are compared with experimental spectra. For the iron spectrum, the degree of congruence is moderate to good, which may be attributed to a lack of precise atomic and Stark broadening data as well as a simplified plasma model. The line profile of the Al resonance line with self reversal can be simulated with a high degree of agreement. Simulated spectra of a steel sample in the vacuum ultraviolet spectral range demonstrate the strong influence of the ambient atmosphere in the spectral range between 178 and 194 nm. The number of free parameters of the plasma model of 8 can be further reduced down to 3, taking into account the integral parameters of the plasma that are accessible experimentally.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
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