共查询到20条相似文献,搜索用时 46 毫秒
1.
Ali Khumaeni Zener Sukra Lie Hideaki Niki Ken-ichi Fukumoto Tadashi Maruyama Kiichiro Kagawa 《Optical Review》2010,17(3):285-289
The analysis of hydrogen in a metal sample (zircaloy-4), which is usually difficult to perform using conventional laser-induced
breakdown spectroscopy (LIBS) techniques, has been achieved using a double-pulse technique under He gas at atmospheric pressure.
In this technique, a transversely excited atmospheric-pressure (TEA) CO2 laser (1.5 J, 200 ns) was focused onto the metal surface to induce a strong He gas plasma whilst simultaneously focussing
a Nd-doped yttrium aluminum garnet (Nd:YAG) laser (120 mJ, 8 ns), synchronized with the TEA CO2 laser, onto the metal to ablate
atoms into the resulting He gas plasma. The emission spectrum obtained shows a narrow H linewidth with low background intensity
and long lifetime emission, thereby indicating that excitation takes place via metastable He atoms. The H emission from H2O can be suppressed by a careful pretreatment involving heating the sample in a vacuum chamber. 相似文献
2.
AbstractA comprehensive review of important progress achieved over the last 30 years regarding knowledge of laser-induced plasmas generated by CO2 and Nd:YAG lasers in a variety of ambient gases is presented in this article, as well as research results on the extension of laser-induced breakdown spectroscopy (LIBS) for quantitative analysis of light elements, especially hydrogen and deuterium. First, the formation of shock wave–induced expanding secondary plasma in low-pressure ambient gases is discussed along with the dynamic characteristics of the secondary plasma expansion process. The unique advantages of low-pressure gas plasma are explained in relation to the successful detection of the sharp H and D emission lines. The experimental results using helium ambient gas are presented with emphasis on the role of He gas plasma in introducing an additional delayed excitation mechanism involving the helium metastable excited state, which resulted in the complete resolution of H and D emission lines, separated by only 0.18 nm. The development of a laser precleaning treatment and special double-pulse techniques further produced a linear calibration line with zero intercept applicable to quantitative H and D analyses of zircaloy sample, with either low- or high-pressure ambient He gas. More recent use of a transversely excited atmospheric (TEA) CO2 laser in place of an Nd:YAG laser has demonstrated the much desired larger excited helium plasma and thereby resulted in significant emission enhancement and improved detection sensitivity. 相似文献
3.
In plasma material processing, vacuum ultraviolet (VUV) emission is released from gas discharges, leading to undesirable results. Energetic VUV photons enable the creation of an electron-hole pair current when their energy is larger than the bandgap energy of the plasma-facing top layer during plasma material processing. For example, the high energy of VUV photons from helium (21.2 eV), argon (11.6 eV), and oxygen (13.6 eV) is sufficient to generate induced currents in SiO2 thin films. These feedstock gases are widely used in many procedures utilizing low-temperature industrial plasmas. Thus, the VUV emission evolution with both the power ratio between high (60 MHz) and low (2 MHz) frequencies and pulse duty ratio of the low-frequency radio frequency (rf) power in a dual-frequency capacitively coupled plasma, which is indispensable in modern plasma etching processes, was investigated. Both the power ratio between high and low frequencies and the pulse duty ratio changed the electron temperature, leading to evolution of the VUV emission intensity. 相似文献
4.
B.?Niermann M.?B?ke N.?Sadeghi J.?Winter 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(3):489-495
Space resolved concentrations of helium He* (3S1) and argon Ar* (3P2)
metastable atoms in an atmospheric pressure radio frequency micro-plasma jet were measured using tunable diode laser absorption
spectroscopy. Even small absorptions down to 10-4 could be measured using lock-in technique. The absolute density of metastable
atoms densities at different rf-power, flow rate and gas mixture was deduced from measured absorption rates. Metastable
concentrations range from 109 to 1011 cm-3. Analysis of spectral profiles provided the pressure broadening coefficients
of both metastable atoms by helium. The spatial distribution of metastable atoms in the plasma volume was obtained for various
discharge
conditions. Density profiles between the electrodes reveal the sheath structure and reflect the plasma excitation distributions
in the
discharge volume. It reveals the dominance of the α-mode discharge. 相似文献
5.
Koo Hendrik Kurniawan 《应用光谱学评论》2013,48(2):99-130
Abstract Hydrogen emission in laser plasma has been studied by focusing a TEA CO2 laser and Nd‐YAG lasers on various types of samples, such as glass, quartz, and zircaloy pipes doped with hydrogen. It was found that Hα emission with a narrow spectral width occurs with high efficiency when the laser plasma is produced in low‐pressure host gas. In contrast, the conventional well‐known laser‐induced breakdown spectroscopy (LIBS), which operates at atmospheric air pressure, cannot be applied for the analysis of hydrogen as impurity. The specific characteristic of hydrogen emission in low‐pressure plasma is interpreted on the basis of our shock wave model, taking account of the fact that the hydrogen mass is extremely light compared to that of the host target. Another experimental study on gas analysis was conducted using an Nd‐YAG laser and helium host gas at atmospheric pressure on a sample of mixed water (H2O) and heavy water (D2O) in vapor form. It was shown that completely resolved hydrogen (Hα) and deuterium (Dα) emission lines that are separated by only 0.179 nm could be obtained at a properly delayed detection time when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared. It is argued that a helium metastable excited state plays the important role in the hydrogen excitation process. 相似文献
6.
M. Pardede R. Hedwig M.M. Suliyanti Z.S. Lie T.J. Lie D.P. Kurniawan K.H. Kurniawan M. Ramli K. Fukumoto H. Niki S.N. Abdulmadjid N. Idris T. Maruyama K. Kagawa M.O. Tjia 《Applied physics. B, Lasers and optics》2007,89(2-3):291-298
An experimental study has been performed to demonstrate the advantage of employing ambient helium gas in the spectral quality
improvement of hydrogen emission in laser-induced plasma from zircaloy-2 samples at both atmospheric and low gas pressure.
It was further shown that the optimal results achieved in the two pressure regimes require the adoption of different sets
of experimental parameters consisting of the laser energy, the focusing lens position and the detection gate delay. A strictly
linear calibration line with extrapolated zero intercept was nevertheless exhibited in the case of atmospheric gas pressure
only. Additional time-evolution measurement of the emission intensities of hydrogen, helium and zirconium clearly suggests
a distinctly different excitation mechanism for hydrogen atoms associated with the presence of ambient helium atoms and their
meta-stable excited state.
PACS 52.38 Mf 相似文献
7.
《Current Applied Physics》2007,7(5):540-546
A TEA CO2 laser beam (500 mJ, 200 ns) was focused on film samples, under low pressure surrounding gas at around 1 Torr. It has been found that to generate the laser plasma for the sample of oil or powder, the sample should be attached in the form of thin film on the surface of a metal, such as copper plate, which acts as a sub-target. The plasma has favorable characteristics for spectrochemical analysis due to its low background and sharp line spectrum, and hence an optical multichannel analyzer (OMA) without gated function can be used for spectrum acquisition. Using the sub-target effect we have performed for analyses on water molecular layer and water impurities, where the water was condensed by heating process or electrolysis process on the sub-target so that impurities in the water were attached to the metal surface. It should be emphasized that in this case the sub-target itself has never been ablated and no any damaged on its surface. Another application of the sub-target effect is used for the analysis of oil contamination in soils. We have succeeded to detect clearly the emission line of C I 247.9 nm from the carbon as a major constituent of the oil. To derive the carbon emission intensity coming only from oil, compensation was made to cancel the contribution from other organic species using the emission of Ca, which inherently contains in other organic species in soil. As result, a good linear relationship between carbon emission intensity and oil concentration was obtained. 相似文献
8.
M. Ramli K. Kagawa S.N. Abdulmadjid N. Idris W.S. Budi M.A. Marpaung K.H. Kurniawan T.J. Lie M.M. Suliyanti R. Hedwig M. Pardede Z.S. Lie M.O. Tjia 《Applied physics. B, Lasers and optics》2007,86(4):729-734
A study of the experimental results on the plasma emissions of water and ethanol vapor samples, induced by Nd:YAG laser in
ambient helium and nitrogen gases at atmospheric pressure, is presented here. The result reveals distinct geometrical and
spectral characteristics of the plasma emissions generated in the helium gas when compared to those observed from nitrogen
gas plasma. Most remarkable is the narrow line width and low continuum background exhibited by emission lines of the analyte
atoms from helium plasma, including the hydrogen emission line which is known to suffer from notorious broadening effects
in conventional laser induced breakdown spectroscopy (LIBS). It is further shown on the basis of the measured spatial distributions
and time profiles of the emission intensities, that the excellent spectral quality is attained by taking advantage of the
meta-stable excited state of helium atoms for the delayed excitation of the hydrogen and other analyte atoms, this allows
the detection of those atomic emissions to be performed under more favorable conditions. The result of this study has thus
demonstrated the feasibility of achieving high-quality spectrochemical analysis, including hydrogen analysis with laser-induced
helium gas breakdown spectroscopy.
PACS 52.38.Mf 相似文献
9.
《Current Applied Physics》2014,14(3):451-454
Taking advantages of the special characteristics of a transversely excited atmospheric (TEA) CO2 laser, the analysis of sodium aerosol has been successfully conducted by using laser-induced gas plasma spectroscopy (LIGPS) method. In this study, the sodium aerosol was deposited on a nickel metal plate; the metal plate functions as a subtarget to initiate a gas plasma. When a pulsed TEA CO2 laser was focused on the metal surface, a large-volume and high-temperature gas plasma was induced. The fine particles of sodium then entered into the gas plasma region to be dissociated and excited. By using this technique, a semi quantitative analysis of sodium aerosol was made. The detection limit of sodium was approximately 200 ppb. 相似文献
10.
Selenium is determined by atomic emission technique with microwave induced helium plasma as the excitation source. A continuous hydride generation system using a peristaltic pump, an effective serpentine hydride generator and a gas-liquid separator is developed and interfaced to the He-plasma. The selenium hydride and the reaction by-products are carried directly and continuously by the He carrier gas (0.6 L/min) into the plasma sustained in a tangential torch. The power level is 100 W and the tangential helium flow-rate is 4.5 L/min. The detection limit (3 0) is 40 ppb, the linear dynamic range is over three orders of magnitude, and the precision is 6.7% RSD for a 1 ppm solution. Applications to a soil sample showed comparable results to a conventional hydride generation atomic absorption system. 相似文献
11.
《Current Applied Physics》2014,14(3):467-471
A clad-modified fiber optic sensor with nanocrystalline CeO2 is proposed for gas detection. As-prepared and annealed CeO2 (500 °C) samples have been used as gas sensing media. The spectral characteristics of the fiber optic gas sensor are studied for various concentrations of ammonia, ethanol and methanol gases (0–500 ppm). The sensor exhibits linear variation in the spectral peak intensity with the gas concentration. The characteristics of the sensor are also studied for gas selectivity. The time response characteristics of the sensor are reported. 相似文献
12.
发射光谱法是对等离子进行在线诊断的常用方法。在丙酮/H2、丙酮/H2/He和丙酮/H2/Ar三种体系中,对热丝化学气相沉积金刚石薄膜过程中的等离子体进行了在线测量。研究了不同体积分数的惰性气体对等离子体中各活性基团强度的影响,以及CH,H与C2的相对强度的比值、电子温度的大小随惰性气体体积分数的变化关系。结果表明,各基团的强度随着惰性气体体积分数的增加呈现上升趋势,且加入同体积分数的氩气比加入氦气的影响更大;CH,H与C2的相对强度比值、电子温度随着惰性气体体积分数的增加而呈现下降趋势,且在丙酮/H2/Ar体系中要比丙酮/H2/He体系中小。 相似文献
13.
A new seeded velocity measurement technique, N2O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO
tag line. Nitrous oxide “laughing gas” is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N2O to O(1D) that subsequently reacts with N2O to form NO. O2 fluorescence induced by the ArF laser “writes” the original position of the NO line. After a time delay, the shifted NO line
is “read” by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with
4% N2O in air, ∼1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations
predict 800–1200 ppm of NO for 190–750 K at 1 atm and 850–1000 ppm of NO for 0.25–1 atm at 190 K. Decreasing the gas pressure
(or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation.
The very short NO formation time (<10 ns) makes the N2O MTV method amenable to low- and high-speed air flow measurements. The N2O MTV technique is demonstrated in air jet to measure its velocity profile. The N2O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of
N2O with O(1D) from N2O photodissociation and thus does not depend on the bulk gas composition. 相似文献
14.
C.G. Teodoro D.U. Schramm M.S. Sthel G.R. Lima M.V. Rocha J.R. Tavares H. Vargas 《Infrared Physics & Technology》2010,53(2):151-155
In this work, CO2 laser photoacoustic spectroscopy was used to detect and monitor ethylene concentrations from about 0.6 ppmV up to 47 ppmV emitted by urban public transports in Campos dos Goytacazes city in Rio de Janeiro state, Brazil. The photoacoustic method proved to be a very sensitive and selective gas detection technique. As ethylene is a rather reactive compound due to its double bond between the two carbon atoms, it acts as one of the precursors for the tropospheric ozone generation, a gas species that is present in the photochemical smog, is an important greenhouse gas and whose formation is strongly associated with the presence of sun light and nitrogen oxide compounds. For this reason, ethylene renders itself an important pollutant in the atmosphere. In addition, the valid Brazilian legislation is only concerned with the total emission of hydrocarbons from the vehicle exhausts. It means that it does not discriminate the emission of some pollutant gas compounds, such as ethylene. This situation is greatly aggravated by the fact that most of the mass and cargo transport in Brazil is made by roads and powered by diesel oil. 相似文献
15.
A near-infrared (NIR) dual-channel differential acetylene (C2H2) detection system was experimentally demonstrated based on tunable diode laser absorption spectroscopy (TDLAS) technique and wavelength modulation spectroscopy (WMS) technique. A distributed feedback (DFB) laser modulated by a self-developed driver around 1.534 μm is used as light source. A miniature gas chamber with 15 cm path length is adopted as absorption pool, and an orthogonal lock-in amplifier is developed to extract the second harmonic (2f) signal. Sufficient standard C2H2 samples with different concentrations were prepared, and detailed measurements were carried out to study the detection performance. A good linear relationship is observed between the amplitude of the 2f signal and C2H2 concentration within the range of 200–10,000 ppm, and the relative measurement error is less than 5% within the whole range. A long-term monitoring lasting for 20 h on a 1000 ppm C2H2 sample was carried out, and the maximum concentration fluctuation is less than 2%. Due to the capability of using long-distance and low-loss optical fiber, the gas-cell can be placed in the filed for remote monitoring, which enables the system to have good prospects in industrial field. 相似文献
16.
In this work, the uniform and vertically aligned single wall carbon nanotubes (SWCNTs) have been grown on Iron (Fe) deposited Silicon (Si) substrate by plasma enhanced chemical vapor deposition (PECVD) technique at very low temperature of 550 °C. The as-grown samples of SWCNTS were characterized by field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM) and Raman spectrometer. SWCNT based chemiresistor gas sensing device was fabricated by making the proper gold contacts on the as-grown SWCNTs. The electrical conductance and sensor response of grown SWCNTs have been investigated. The fabricated SWCNT sensor was exposed to ammonia (NH3) gas at 200 ppm in a self assembled apparatus. The sensor response was measured at room temperature which was discussed in terms of adsorption of NH3 gas molecules on the surface of SWCNTs. The achieved results are used to develope a miniaturized gas sensor device for monitoring and control of environment pollutants. 相似文献
17.
W. Hardjoutomo H. Munechika H. Kurniawan I. Hattori T. Kobayashi K. Kagawa 《Optics & Laser Technology》1992,24(5)
A compact capacitor-transfer TEA CO2 laser of 180 mJ output energy and 50 ns pulse duration in half width was designed and constructed for field use. This laser is suitable for laser microprobe spectrochemical analysis on geological and mining samples. Experiments show that the use of helium as a surrounding gas suppresses the continuous emission spectrum of the plasma, thus increasing the S/N ratio. Using glass as standard samples, the minimum detectable concentrations are estimated with Zn neutral line and F ionic line to be 60 ppm and 500 ppm, respectively. 相似文献
18.
We present the results of studies of the optical characteristics and parameters of a gas discharge plasma produced by a barrier
discharge at atmospheric pressure, based on a mixture of mercury dibromide vapor and helium (the working medium of a small
(emitting area 8 cm2) exciplex gas discharge emitter). An average emission power of 70 mW (λmax = 502 nm) was achieved for pump pulse repetition frequency 6 kHz, voltage pulse amplitude 2.3 kV, and current pulse amplitude
8 A of duration ~100 nsec. We established the plasma parameters: the electron energy distribution functions, the transport
characteristics, the discharge power losses per unit pressure going toward electron processes, the electron concentration
and temperature, and also the rate constants for processes of elastic and inelastic scattering of electrons by the components
of the working mixture as a function of the parameter E/N, where E is the electric field strength and N is the total concentration
of mercury dibromide molecules and helium atoms. 相似文献
19.
A sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was evaluated for the detection of trace levels of ethylene
at atmospheric pressure using a fiber coupled DFB diode laser emitting in the 1.62 μm spectral range. A noise-equivalent QEPAS signal of ∼4 ppm C2H4 was achieved for a 0.7 s data acquisition time using wavelength-modulation with a second-harmonic detection scheme on the
strongest C2H4 absorption peak at 6177.14 cm−1 with an average optical power of ∼15 mW. Improved detection sensitivity of 0.5 and 0.3 ppm C2H4 (1σ) was demonstrated using longer averaging time of 70 and 700 s, respectively. Important characteristics for the QEPAS based
sensor operation in real-world conditions are presented, particularly the influence of external temperature variations. Furthermore,
the response time of the ethylene sensor was measured in different configurations and it is shown that the QEPAS technique
can provide a response time in a few seconds range even without active gas flow. 相似文献
20.
M.I. Katı M. Türemis I.C. Keskin B. Tastekin R. Kibar A. Çetin N. Can 《Journal of luminescence》2012,132(10):2599-2602
Natural blue-green beryl from Turkey has been investigated using scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and Cathodoluminescence (CL). Beryl has the chemical formula Be3Al2Si6O18 and is hexagonal with space group P6/mcc. Chemical analyses of the beryl sample utilised inductively coupled plasma-atomic emission spectroscopy (ICP-AES) for major oxides and trace elements. It shows that the beryl sample is rich in Cs (531 ppm) and contains low concentrations of transition-metal ions, in total 2.29 wt.% Fe, 269 ppm Mn, V<5 ppm and Cr 20 ppm. Ideas on the origin of the green colour of this mineral are presented. The CL spectrum of the bulk sample display intense broad band emission from ~360 to ~800 nm. 相似文献