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Christian G Parigger - One of the best experts on this subject based on the ideXlab platform.
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hydrogen alpha laser ablation plasma diagnostics
Optics Letters, 2015Co-Authors: Christian G Parigger, David M. Surmick, Ghaneshwar Gautam, A El M SherbiniAbstract:Spectral measurements of the Hα Balmer Series line and the continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2×1024 m−3 are determined from absolute calibrated emission coefficients for time delays of 100–650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5–0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The redshifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The electron densities inferred from power law formulas agree with the values obtained from the plasma emission coefficients.
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asymmetric hydrogen beta electron density diagnostics of laser induced plasma
Spectrochimica Acta Part B: Atomic Spectroscopy, 2014Co-Authors: Christian G Parigger, Lauren D. Swafford, David M. Surmick, Alexander C. Woods, Michael J. WitteAbstract:Abstract The hydrogen beta line has been widely used in determining plasma parameters such as electron density. In conjunction with other Balmer Series lines, electron temperature can be inferred. The asymmetric appearance of the hydrogen beta line, due to quadrupole interactions, can be utilized as well for the determination of electron density. Laser-induced optical breakdown is generated in laboratory air, and particularly for electron densities in the range of 0.3 to 1.0 × 10 17 cm − 3 the use of the asymmetry parameter is elaborated for electron density diagnostics. Also included are results of analysis of the hydrogen beta profiles for which the asymmetry indicates an electron density on the order of 2.0 × 10 18 cm − 3 , which is significantly higher than 6.3 to 6.8 × 10 17 cm − 3 maximum that was measured previously from the Stark-broadened hydrogen beta width following laser-induced optical breakdown.
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Laser-Induced Plasma Spectroscopy of Hydrogen Balmer Series in Laboratory Air
Applied spectroscopy, 2014Co-Authors: Lauren D. Swafford, Christian G PariggerAbstract:Stark-broadened emission profiles for the hydrogen alpha and beta Balmer Series lines in plasma are measured to characterize electron density and temperature. Plasma is generated using a typical laser-induced breakdown spectroscopy (LIBS) arrangement that employs a focused Q-switched neodymium-doped yttrium aluminum garnet (Nd : YAG) laser, operating at the fundamental wavelength of 1064 nm. The temporal evolution of the hydrogen Balmer Series lines is explored using LIBS. Spectra from the plasma are measured following laser-induced optical breakdown in laboratory air. The electron density is primarily inferred from the Stark-broadened experimental data collected at various time delays. Due to the presence of nitrogen and oxygen in air, the hydrogen alpha and beta lines become clearly discernible from background radiation for time delays of 0.4 and 1.4 μs, respectively.
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Atomic and molecular emissions in laser-induced breakdown spectroscopy
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: Christian G PariggerAbstract:Abstract This article summarizes measurements and analysis of hydrogen Balmer Series atomic lines following laser-induced optical breakdown. Electron number density on the order of 1 × 1025 m− 3 can be measured using Hα Stark width and shift in the analysis of breakdown plasma in 1 to 1.3 × 105 Pa, gaseous hydrogen. The Hβ line can be utilized for electron number density up to 7 × 1023 m− 3. The historic significance is elaborated of accurate Hβ measurements. Electron excitation temperature is inferred utilizing Boltzmann plot techniques that include Hγ atomic lines and further members of the Balmer Series. Laser ablation of aluminum is discussed in view of limits of application of the Balmer Series. Hβ and Hγ lines show presence of molecular carbon in a 2.7 and 6.5 × 105 Pa, expanding methane flow. Diagnostic of such diatomic emission spectra is discussed as well. Laser-induced breakdown spectroscopy historically embraces elemental analysis, or atomic spectroscopy, and to a lesser extent molecular spectroscopy. Yet occurrence of superposition spectra in the plasma decay due to recombination or due to onset of chemical reactions necessitates consideration of both atomic and molecular emissions following laser-induced optical breakdown. Molecular excitation temperature is determined using so-called modified Boltzmann plots and fitting of spectra from selected molecular transitions. The primary interest is micro-plasma characterization during the first few micro-seconds following optical breakdown, including shadowgraph visualizations.
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Balmer Series Hbeta measurements in a laser-induced hydrogen plasma.
Applied optics, 2003Co-Authors: Christian G Parigger, David H. Plemmons, Eugene OksAbstract:Stark-broadened emission profiles of the Balmer Series Hbeta lines are measured subsequent to nanosecond laser-induced optical breakdown in gaseous hydrogen. Electron number densities are found from time-resolved spectra from Hbeta emissions to be in the range 10(15)-10(18) cm(-3). These results are compared with Halpha measurements for which number densities as high as 10(19) cm(-3) are determined from Stark widths and Stark shifts. Good agreement is reported for number densities inferred from Halpha and Hbeta emissions, down to an electron number density 3 x 10(16) cm(-3), by accurate treatment of ion dynamics in the theory.
David M. Surmick - One of the best experts on this subject based on the ideXlab platform.
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Laser plasma diagnostics and self-absorption measurements of the Hβ Balmer Series line
Journal of Quantitative Spectroscopy and Radiative Transfer, 2016Co-Authors: Ghaneshwar Gautam, David M. Surmick, Ashraf M. El SherbiniAbstract:Abstract In this work, the peak-separation of the Balmer Series hydrogen beta line was measured to determine the electron density of laser-induced plasma from spatially and temporally resolved spectra collected in laboratory air at standard ambient temperature and pressure. The self-absorption phenomenon is investigated by using a mirror that retro-reflects the emitted radiation through the plasma. The experimental data with and without the mirror were analyzed with available hydrogen beta computer simulations. Hardly any self-absorption was found as indicated by the correction factors that only marginally differ from unity. The obtained electron density values are also compared with the electron densities from nearby nitrogen lines. The hydrogen beta H β peak-separation method yields reliable results for an electron density of the order of 1 × 10 17 cm − 3 for time delays of 5 μ s from plasma generation, which confirms that self-absorption is insignificant for such electron densities.
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hydrogen alpha laser ablation plasma diagnostics
Optics Letters, 2015Co-Authors: Christian G Parigger, David M. Surmick, Ghaneshwar Gautam, A El M SherbiniAbstract:Spectral measurements of the Hα Balmer Series line and the continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2×1024 m−3 are determined from absolute calibrated emission coefficients for time delays of 100–650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5–0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The redshifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The electron densities inferred from power law formulas agree with the values obtained from the plasma emission coefficients.
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Hydrogen Balmer Series Measurements in Laser-Induced Air Plasma
Journal of Physics: Conference Series, 2014Co-Authors: Lauren D. Swafford, David M. Surmick, Michael J. Witte, Alexander C. Woods, Ghaneshwar GautamAbstract:Time-resolved spectroscopy is employed to analyze micro plasma generated in laboratory air. Stark-broadened emission profiles for hydrogen alpha and beta allow us to determine plasma characteristics for specific time delays after plasma generation. Stark shift, asymmetry, and full width half maximum measurements are used to infer electron density. The measurements of hydrogen alpha and beta Balmer Series line shapes are analyzed using various theory results. Our laser-induced breakdown spectroscopy arrangement uses a Q- switched Nd:YAG laser operating at the fundamental wavelength of 1064 nm that is focused for plasma generation. The hydrogen alpha and beta lines emerge from the free electron background radiation for time delays larger than 0.3 ps and 1.4 ps, respectively. Neutral and ionized nitrogen emission lines allow us to infer electron density for time delays from 0.1 to 10 μs. The electron density values are compared with results obtained from hydrogen Balmer Series line shapes.
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asymmetric hydrogen beta electron density diagnostics of laser induced plasma
Spectrochimica Acta Part B: Atomic Spectroscopy, 2014Co-Authors: Christian G Parigger, Lauren D. Swafford, David M. Surmick, Alexander C. Woods, Michael J. WitteAbstract:Abstract The hydrogen beta line has been widely used in determining plasma parameters such as electron density. In conjunction with other Balmer Series lines, electron temperature can be inferred. The asymmetric appearance of the hydrogen beta line, due to quadrupole interactions, can be utilized as well for the determination of electron density. Laser-induced optical breakdown is generated in laboratory air, and particularly for electron densities in the range of 0.3 to 1.0 × 10 17 cm − 3 the use of the asymmetry parameter is elaborated for electron density diagnostics. Also included are results of analysis of the hydrogen beta profiles for which the asymmetry indicates an electron density on the order of 2.0 × 10 18 cm − 3 , which is significantly higher than 6.3 to 6.8 × 10 17 cm − 3 maximum that was measured previously from the Stark-broadened hydrogen beta width following laser-induced optical breakdown.
J.l. Terry - One of the best experts on this subject based on the ideXlab platform.
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study of the discrete to continuum transition in a Balmer spectrum from alcator c mod divertor plasmas
Plasma Physics and Controlled Fusion, 1998Co-Authors: Yu A Pigarov, J.l. Terry, B LipschultzAbstract:Under detached plasma conditions in the Alcator C-Mod tokamak, the measured spectra show pronounced merging of the Balmer Series lines and a photo-recombination continuum edge which is not a sharp step. This phenomenon, known as a smooth discrete-to-continuum (D-C) transition, is typical only for high-density , low-temperature (Te≈1 eV), and recombining plasma. As we will discuss, this type of transition emphasizes the degree of plasma non-ideality. A theoretical model capable of treating spectra from a detached divertor plasma, and those with a smooth D-C transition in particular, has been developed. It is comprised of three parts: (i) a collisional-radiative model for the population densities of the excited states, (ii) atomic structure and collision rates for an atom affected by statistical plasma microfields, and (iii) a model for calculating the line profiles and the extended photo-recombination continuum. The effects of statistical plasma microfields on the population densities of excited states, on the profiles of Balmer Series lines, and on the photo-recombination continuum edge are discussed. The changes in spectrum characteristics with plasma parameter variation, leading to the smooth D-C transition, are analysed. The relevance of volumetric plasma recombination to the spectra observed from a detached divertor plasma is discussed. A comparison of the calculated and measured spectra is used to determine the plasma parameters in the recombining plasma region. Along with other properties of measured spectrum, the smooth D-C transition provides evidence in support of the recombining state of the plasma attained under detached divertor conditions.
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volume recombination and opacity in alcator c mod divertor plasmas
Physics of Plasmas, 1998Co-Authors: J.l. Terry, D Lumma, Yu A Pigarov, S I Krasheninnikov, H Ohkawa, D A Pappas, M V UmanskyAbstract:Volume recombination within the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] divertor plasma is measured and found to be a significant fraction of the total ion sink under detached divertor conditions. The recombination occurs in regions where Te∼1 eV and ne∼1021 m−3. Measurements of the spatial distribution of the recombination are presented. The determinations of the recombination rates are made by measuring the D0 Balmer spectrum and by using a collisional radiative model describing the level populations, ionization, and recombination of D0. The concept of “recombinations per Balmer Series photon” is developed to simplify the determinations. Measurements of the opacity of Lyβ emission are presented. It is observed that up to 50% of the Lyβ emission is trapped, indicating that Lyα is strongly trapped in some cases. The effects of Lyα,β trapping on the “recombinations per photon” curves are calculated and considered in the recombination rate determinations. Observations indicatin...
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radiative and three body recombination in the alcator c mod divertor
Physics of Plasmas, 1997Co-Authors: D Lumma, J.l. Terry, B LipschultzAbstract:Significant recombination of the majority ion species has been observed in the divertor region of Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] under detached conditions. This determination is made by analysis of the visible spectrum from the divertor, in particular the Balmer Series line emission and the observed recombination continuum, including an apparent recombination edge at ∼375 nm. The analysis shows that the electron temperature in the recombining plasma is 0.8–1.5 eV. The measured volume recombination rate is comparable to the rate of ion collection at the divertor plates. The dominant recombination mechanism is three-body recombination into excited states (e+e+D+⇒D0+e), although radiative recombination (e+D+⇒D0+hν) contributes ∼5% to the total rate. Analysis of the Balmer Series line intensities (from nupper=3 through 10) shows that the upper levels of these transitions are populated primarily by recombination. Thus the brightnesses of the Balmer Series (and Lyman serie...
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density measurements in the edge divertor and x point regions of alcator c mod from Balmer Series emission
Physics of Plasmas, 1995Co-Authors: B. Welch, H. R. Griem, J.l. Terry, C. Kurz, Brian Labombard, Bruce Lipschultz, E.s. Marmar, G.m. MccrackenAbstract:The electron density in the edge, divertor and X‐point regions of Alcator C‐Mod [Proceedings of the IEEE 13th Symposium on Fusion Engineering (Institute of Electrical and Electronic Engineers, New York, 1990), Vol. 1, p. 13] has been measured using the Stark broadening of high‐n (n=8 through 11) transitions of the Balmer Series of deuterium. These measurements have been made during typical single null, diverted operation and during gas‐puffing through capillaries located within the first wall and divertor. Electron densities up to 1.6×1021 m−3 have been measured in the X‐point region and slightly lower densities (5−7×1020 m−3) have been measured in the divertor and edge regions. These results are factors of 2 to 5 larger than the density measurements from the CO2 laser interferometer system in the main chamber (3×1020 m−3) and comparable with probe measurements in the divertor. The ratios of the widths of adjacent lines within the Balmer Series have been compared with ratios calculated for the Stark broad...
Ghaneshwar Gautam - One of the best experts on this subject based on the ideXlab platform.
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Laser plasma diagnostics and self-absorption measurements of the Hβ Balmer Series line
Journal of Quantitative Spectroscopy and Radiative Transfer, 2016Co-Authors: Ghaneshwar Gautam, David M. Surmick, Ashraf M. El SherbiniAbstract:Abstract In this work, the peak-separation of the Balmer Series hydrogen beta line was measured to determine the electron density of laser-induced plasma from spatially and temporally resolved spectra collected in laboratory air at standard ambient temperature and pressure. The self-absorption phenomenon is investigated by using a mirror that retro-reflects the emitted radiation through the plasma. The experimental data with and without the mirror were analyzed with available hydrogen beta computer simulations. Hardly any self-absorption was found as indicated by the correction factors that only marginally differ from unity. The obtained electron density values are also compared with the electron densities from nearby nitrogen lines. The hydrogen beta H β peak-separation method yields reliable results for an electron density of the order of 1 × 10 17 cm − 3 for time delays of 5 μ s from plasma generation, which confirms that self-absorption is insignificant for such electron densities.
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hydrogen alpha laser ablation plasma diagnostics
Optics Letters, 2015Co-Authors: Christian G Parigger, David M. Surmick, Ghaneshwar Gautam, A El M SherbiniAbstract:Spectral measurements of the Hα Balmer Series line and the continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2×1024 m−3 are determined from absolute calibrated emission coefficients for time delays of 100–650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5–0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The redshifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The electron densities inferred from power law formulas agree with the values obtained from the plasma emission coefficients.
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Hydrogen Balmer Series Measurements in Laser-Induced Air Plasma
Journal of Physics: Conference Series, 2014Co-Authors: Lauren D. Swafford, David M. Surmick, Michael J. Witte, Alexander C. Woods, Ghaneshwar GautamAbstract:Time-resolved spectroscopy is employed to analyze micro plasma generated in laboratory air. Stark-broadened emission profiles for hydrogen alpha and beta allow us to determine plasma characteristics for specific time delays after plasma generation. Stark shift, asymmetry, and full width half maximum measurements are used to infer electron density. The measurements of hydrogen alpha and beta Balmer Series line shapes are analyzed using various theory results. Our laser-induced breakdown spectroscopy arrangement uses a Q- switched Nd:YAG laser operating at the fundamental wavelength of 1064 nm that is focused for plasma generation. The hydrogen alpha and beta lines emerge from the free electron background radiation for time delays larger than 0.3 ps and 1.4 ps, respectively. Neutral and ionized nitrogen emission lines allow us to infer electron density for time delays from 0.1 to 10 μs. The electron density values are compared with results obtained from hydrogen Balmer Series line shapes.
G De Holanda Cavalcanti - One of the best experts on this subject based on the ideXlab platform.
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on the determination of plasma electron number density from stark broadened hydrogen Balmer Series lines in laser induced breakdown spectroscopy experiments
Spectrochimica Acta Part B: Atomic Spectroscopy, 2013Co-Authors: L Pardini, S Legnaioli, G Lorenzetti, V Palleschi, R Gaudiuso, A De Giacomo, Diego Diaz M Pace, Anabitarte F Garcia, G De Holanda CavalcantiAbstract:Abstract In this work, different theories for the determination of the electron density in Laser-Induced Breakdown Spectroscopy (LIBS) utilizing the emission lines belonging to the hydrogen Balmer Series have been investigated. The plasmas were generated by a Nd:Yag laser (1064 nm) pulsed irradiation of pure hydrogen gas at a pressure of 2 · 10 4 Pa. H α , Η β , Η γ , Η δ , and H e Balmer lines were recorded at different delay times after the laser pulse. The plasma electron density was evaluated through the measurement of the Stark broadenings and the experimental results were compared with the predictions of three theories (the Standard Theory as developed by Kepple and Griem, the Advanced Generalized Theory by Oks et al., and the method discussed by Gigosos et al.) that are commonly employed for plasma diagnostics and that describe LIBS plasmas at different levels of approximations. A simple formula for pure hydrogen plasma in thermal equilibrium was also proposed to infer plasma electron density using the H α line. The results obtained showed that at high hydrogen concentration, the H α line is affected by considerable self-absorption. In this case, it is preferable to use the H β line for a reliable calculation of the electron density.
