Feasibility of Laser Induced Plasma Spectroscopy for (original) (raw)
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Experiments in Fluids, 2012
In this paper, experimental results obtained with Laser Induced Plasma Spectroscopy to retrieve local compositions are presented for an ambient pressure up to 5.0 MPa in a still cell. Well controlled mixtures of gases are introduced and plasma is obtained with the fundamental emission of a pulsed Nd:YAG laser. Simultaneously, plasma shape and spectrally resolved data are taken with a temporal resolution down to 2 ns. First, the temporal evolutions of a high-pressure nitrogen plasma are analyzed as function of spark energy. It is shown that plasma changes orientation from an elongated shape parallel to the laser line to a perpendicular one in a very short time. Results are reported for both spatial and spectral variations. Afterwards, the effects of increased carbon concentration are discussed in both shape and spectra. It is seen that strong intensity due to the atomic carbon emissions appear for the high-pressure case. From those experiments, calibration strategies are proposed to get equivalence ratio under high pressure conditions with a ratio of carbon versus nitrogen and oxygen. The delay between plasma and measurements is set to 2000 ns and the signal is integrated for 5000 ns, so as to yield a good signal to noise ratio and a good sensitivity of the technique to changes in mixture fraction. Calibration curves are reported for equivalence ratio up to 1.00 and for pressure from 1.0 to 5.0 MPa. It is shown that typical uncertainties are limited to 7.5% regardless the equivalence ratio in a single shot approach using a spectral fit procedure,whereas it accounts to two times more in a more classical peak ratio approach. Increasing the pressure tends to increase the precision as lower pressure had higher uncertainties.
Fundamentals and applications of Laser Induced Plasma Spectroscopy
HAL (Le Centre pour la Communication Scientifique Directe), 2019
The purpose of this article is to review the possibilities provided by the Laser Induced Plasma Spectroscopy measurement technique to get insights into gaseous or spray reacting systems under different working pressure. After a brief review and an overall presentation the requirements of the laser source and the detection systems are described. The processing of the spectral information is discussed before showing typical applications in gaseous, sprays and high-pressure environments. Finally, the potential of LI3PS (LIPS & Ignition & Interferometry) is presented and future directions for developments are given.
Measurements of mixture fraction with Laser Induced Plasma Spectroscopy (特集 燃焼制御における光学計測の応用)
日本燃焼学会誌, 2008
Laser Induced Plasma Spectroscopy (LIPS) is a technique aiming at obtaining mixture fraction inside practical combustor. The fundamental bases of the technique are first exposed and effects of pressure or blended fuels are discussed. A typical experimental setup is discussed as far as the application of LIPS to high-pressure is concerned. Some results obtained in combining LIPS and laser ignition are presented and discussed. Finally, strategies for global control are presented, in which plasma spectroscopy is becoming a sensor-actuator, quite unique and with several interesting possibilities.
2012
An extension of the Laser Induced Plasma Spectroscopy technique has been presented to achieve a very high spatial resolution. It is based on the simultaneous recording of the plasma with cameras equipped with different interferential filter centered on the main atomic emission wavelengths. For mixing between air and nitrogen, emissions of N(744) and O(777) are used whereas for ignition tests, H(656) is chosen for the fuel and O(777) for the oxidizer. Exact calibration procedure is explained and typical results obtained in a laminar burner using air and nitrogen are presented. This technique can be easily coupled to other planar images, like Particle Image Velocimetry to yield simultaneous velocity and scalar information. Typical uncertainties were quantified in a laminar burner and are lower than classic (0D) LIPS approaches. A procedure to obtain spatially resolved energy deposition has been proposed based both on the mixture fraction measurement and the absolute intensity of oxyge...
Applied Physics B, 2006
A comprehensive experimental study was performed to demonstrate the effects of ambient air pressure on the emission characteristics of analyte elements in a variety of host materials in laser-induced plasma spectroscopy in low ambient air pressures. It was shown that the pressure-dependent characteristics of the emission lines are generally influenced by host elements when significant mass difference exists between the analyte and the host elements. Further investigation on the time profiles of the spatially integrated emission intensities reveal the important interplay among the dynamical factors associated with the mass-difference effect, which effectively influence the shock wave excitation process and hence the related emission intensities. The result of this study also indicates the need of proper control of time delay for the detection of maximum emission intensity in the cases considered.
Laser plasma plume kinetic spectroscopy of the nitrogen and carbon species
Contributions to Plasma Physics, 2003
The formation and decay of carbon and nitrogen atoms, CN radicals and C2 molecules were monitored using spatial-and time-resolved emission spectroscopy in a plasma plume formed during laser ablation of a graphite target in nitrogen atmosphere. A simple exponential model was used to explain the effect of the individual chemical reactions and plasma dynamics on the measured kinetic characteristics. The succession of emissions C → N → CN was observed in the time-resolved spectra, supporting the suggestion that the CN radical is formed mainly by the direct reaction C + N → CN or C2+ N2 → 2 CN. The formation of CN radical was enhanced by the additional generation of atomic nitrogen through the RF discharge.
Laser-induced plasma as a function of the laser parameters and the ambient gas
2014
Laser-induced breakdown spectroscopy (LIBS) has been invented for more than 50 years, which analyzes the spectrum of the laser-induced plasma to determine the elemental composition of the ablated sample. Recently, LIBS technique has been well developed and applied in different domains, for example oceanic exploration, pollution monitoring in the environment. LIBS uses the ablation plasma as a light source that contains the elemental composition information of the sample. However, the laser-induced plasma exhibits a transient behavior. Although time-resolved and gated detection can greatly improve the performance of the LIBS technique especially that of calibration-free LIBS (CF-LIBS) with a better determination of plasma temperature, the temporal evolution of the plasma is correlated to its morphology and its spatial inhomogeneity. The determination of the morphology as well as the internal structure of the plasma together with their evolution during plasma expansion into the ambien...