• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.6
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• pp.479-487
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• 2020

A new double-pulse laser system that combines Raman and laser induced plasma spectroscopy (LIPS) in a single unit is proposed. The study attempts to enhance the laser induced plasma signals while simultaneously extracting the desired molecular signals from Raman spectroscopy. In low pressure conditions such as the lunar atmosphere, the measuring of plasma emission is hard because of the low electron density and short persistence time causing a rapid plasma expansion. Furthermore, in the integration of the detecting system aimed at space exploration, the minimization of laser system is important in terms of the payload mass. Simultaneous molecular and atomic detection that gave highly resolved spectral data at pressure below 0.07 torr is demonstrated amongst eight rock samples test. The plasma stacking produced from the double-pulse laser enhanced the signal intensity of calcium and oxygen lines in calcite matrix by twofold, compared to a conventional LIPS.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.9-17
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• 2020

In this study, the surface changes of titanium alloy using laser surface treatment and the surface analysis using laser-induced plasma spectroscopy were carried out. The laser surface treatment induced changes in surface roughness and the diffusion of atmospheric elements. Excessive melting or less melting caused roughness changes, but when moderate levels of energy were applied, a smoother surface could be obtained than the initial surface. In the process, the diffusion of atmospheric elements took place. To analyze the diffusion of atmospheric elements with respect to surface morphology, the surfaces were re-shaped with grinding. In this experimental conditions, the effect of plasma formation by surface roughness was identified. Compensated plasma signals for the material properties were obtained and analysed by removing the background plasma signal.

• Analytical Science and Technology
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• v.32 no.4
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• pp.121-130
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• 2019

Alumina is one of the most important ceramic materials because of its useful physical and chemical properties. Recently, high-purity alumina has been used in various industrial fields. This leads to increasing demand for reliable elemental analysis of impurities in alumina samples. However, the chemical inertness of alumina makes the sample preparation for conventional elemental analysis a tremendously difficult task. Herein, we demonstrated the feasibility of laser ablation for effective sampling of alumina powder. Laser ablation performs sampling rapidly without any chemical reagents and also allows simultaneous optical emission spectroscopy and mass spectrometry analyses. For six alumina samples including certified reference materials and commercial products, laser-induced breakdown spectroscopy (LIBS) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) analyses were performed simultaneously based on a common laser ablation sampling. LIBS was found to be useful to quantify alkali and alkaline earth metals with limits-of-detection (LODs) around 1 ppm. LA-ICP-MS could quantify transition metals such as Ti, Cu, Zn, and Zr with LODs in the range from a few tens to hundreds ppb.

• Analytical Science and Technology
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• v.33 no.2
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• pp.86-97
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• 2020

Reconstruction and separation of explosive-contaminated overlapping fingerprints constitutes an analytical challenge of high significance in forensic sciences. Laser-induced breakdown spectroscopy (LIBS) allows real-time chemical mapping by detecting the light emissions from laser-induced plasma and can offer powerful means of fingerprint classification based on the chemical components of the sample. During recent years LIBS has been studied one of the spectroscopic techniques with larger capability for forensic sciences. However, despite of the great sensitivity, LIBS suffers from a limited detection due to difficulties in reconstruction of overlapping fingerprints. Here, the authors propose a simple, yet effective, method of using chemical mapping to separate and reconstruct the explosive-contaminated, overlapping fingerprints. A Q-switched Nd:YAG laser system (1064 nm), which allows the laser beam diameter and the area of the ablated crater to be controlled, was used to analyze the chemical compositions of eight samples of explosive-contaminated fingerprints (featuring two sample explosive and four individuals) via the LIBS. Then, the chemical validations were further performed by applying the Raman spectroscopy. The results were subjected to principal component and partial least-squares multivariate analyses, and showed the classification of contaminated fingerprints at higher than 91% accuracy. Robustness and sensitivity tests indicate that the novel method used here is effective for separating and reconstructing the overlapping fingerprints with explosive trace.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.99-101
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• 2013

The equivalence ratio is measured by LIBS(Laser-induced Breakdown spectroscopy) in hydrocarbon flame and high temperature (${\sim}3200^{\circ}C$) oxyhydrogen flame, where a stoichiometric mixture of hydrogen and oxygen is produced from water through electrolysis. The ratio of the hydrogen and oxygen (H/O) atomic lines intensities is used for quantitatively determining the quivalence ratio. laser energy is evaluated for determining the optimal condition for plasma diagnostics. The minimum laser energy for generating plasma in a laminar premixed hydrocarbon flame was about 70 mJ, whereas oxyhydrogen flame. consequently the irradiated spot of a lower density in high temperature oxyhydrogen flame gave rise to bigger plasma in size, thus limiting the spatial resolution of the LIBS measurement.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.451-457
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• 2011

A short laser pulse irradiates a sample to create the highly energetic plasma that emits light of a specific wavelength peak according to the material. By identifying different peaks for the analyzed samples, its chemical composition can be rapidly determined. The LIBS (Laser-Induced Breakdown Spectroscopy) has great advantages as an elemental analyzer on board a space rover, namely real-time rapid analysis and stand-off detection. The LIBS signal intensity is remarkably increased by using double-pulse LIBS system for component analysis of lunar environments where the surrounding pressure is low. Also the angle of target is adjusted for replicating arbitrary shapes of the specimen.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.50-54
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• 2014

In this paper we studied the laser-induced crater depth, mass, and emission spectra of laser-ablated high-density polyethylene (HDPE) polymer using the laser-induced plasma spectroscopy (LIPS) technique. This study was performed using a Nd:YAG laser with 100 mJ energy and 7 ns pulse width, focused normal to the surface of the sample. The nanoscale change in ablated depth versus number of laser pulses was studied. By using scanning electron microscope (SEM) images, the crater depth and ablated mass were estimated. The LIPS spectral intensities were observed for major and minor elements with depth. The comparison between the LIPS results and SEM images showed that LIPS could be used to estimate the crater depth, which is of interest for some applications such as thin-film lithography measurements and online measurements of thickness in film deposition techniques.

• Analytical Science and Technology
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• v.22 no.2
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• pp.141-147
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• 2009

A laser induced breakdown spectroscopy (LIBS) measurement was carried out to derive an optimized measurement condition with a high reproducibility and to grow a plasma sphere to 20 mm high under a 600 mtorr vacuum in order to improve an accuracy of measurement. The measurement of the plasma was taken at a 6.0 mm distance, in the direction of a plasma sphere, from a sample. This location belongs to the outer sphere region in the plasma. The calibration curve of 'Ni' and 'Cu' was acquired by the signal intensity ratio and the atomic ratio for the samples, and linear regression of 'Cu' was $R^2$=0.9886, and the linear regression of 'Ni' was $R^2$=0.9988. The accuracy of LIBS was improved pre-existence as the measurement error of 'Ni' was 0.78%.

• Transactions of the KSME C: Technology and Education
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• v.3 no.4
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• pp.291-297
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• 2015

As promising future energy source, hydrogen has been drawing much attention; however, it is easily leaked from the small gap in any storage container due to its find molecule size. In this study, Laser induced breakdown spectroscopy(LIBS) was used for hydrogen leak detection, and feasibility of the scheme was evaluated based on different way for plasma generation. Laser power of 295 mW was required for generating plasma on metal surface to measure hydrogen atomic emission while approximately 2.5 times higher laser power was needed for plasma formation directly in the hydrogen gas stream. It was shown that peak to base ratio increased linearly with increasing the concentration of hydrogen. It can be concluded that LIBS is a viable technique for hydrogen sensing when the concentration of hydrogen is less than 5%.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.98-99
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• 2012

Deposition of thin films using magnetron sputtering plasmas is a well-developed, classical technology. However, detailed investigations using advanced diagnostics are insufficient in magnetron sputtering, in comparison with plasma-aided dry etching and plasma-enhanced chemical vapor deposition. In this talk, we will show examples of diagnostic works on magnetron sputtering employing metal targets. Diagnostic methods which have fine spatial resolutions are suitable for magnetron sputtering plasmas since they have significant spatial distributions. We are using two-dimensional laser-induced fluorescence spectroscopy, in which the plasma space is illuminated by a tunable laser beam with a planer shape. A charge-coupled device camera with a gated image intensifier is used for taking the picture of the image of laser-induced fluorescence formed on the planer laser beam. The picture of laser-induced fluorescence directly represents the two-dimensional distribution of the atom density probed by the tunable laser beam, when an intense laser with a relatively wide line-width is used. When a weak laser beam with a relatively narrow linewidth is used, the laser-induced fluorescence represents the density distribution of atoms which feel the laser wavelength to be resonant via the Doppler shift corresponding to their velocities. In this case, we can obtain the velocity distribution function of atoms by scanning the wavelength of the laser beam around the line center.