Laser-induced Fluorescence Method Research Articles

Spatial Profile of Ion Velocity Distribution Function in Helicon High-Density Plasma by Laser Induced Fluorescence Method

Spatial Profile of Ion Velocity Distribution Function in Helicon High-Density Plasma by Laser Induced Fluorescence Method

Experimental Research of Reliability of Plant Stress State Detection by Laser-Induced Fluorescence Method

Experimental laboratory investigations of the laser-induced fluorescence spectra of watercress and lawn grass were conducted. The fluorescence spectra were excited by YAG:Nd laser emitting at 532 nm. It was established that the influence of stress caused by mechanical damage, overwatering, and soil pollution is manifested in changes of the spectra shapes. The mean values and confidence intervals for the ratio of two fluorescence maxima near 685 and 740 nm were estimated. It is presented that the fluorescence ratio could be considered a reliable characteristic of plant stress state.

テイラー・ディーン流れを利用したマイクロミキサの研究

Chaotic mixing in three different types of curved-square channel flow has been studied experimentally and numerically. The wall of channel rotates around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. Effects of three different types of moving walls, top and inner walls (B.C.1; Boundary Condition 1), an inner wall (B.C.2; Boundary Condition 2), and a top wall (B.C.3; Boundary Condition 3) on chaotic mixing, have been investigated experimentally and numerically. The secondary flow is measured using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of B.C.1.

Hyperfine structure of the configuration in the Tb atom

Within this work new experimental results concerning the hyperfine structure (hfs) in the terbium atom are presented. Hfs constants A and B for eight levels belonging to the even-parity configuration were determined, based on the results of measurements performed using the laser-induced fluorescence method in a hollow cathode discharge at 18 spectral lines. The configuration in the terbium atom was hitherto very scarcely investigated; for seven of the levels examined within this work results concerning the hfs were obtained for the first time. As a by-product, hfs constants for 12 odd-parity levels, involved as upper levels in the transitions investigated, were also determined. A preliminary attempt at a semi-empirical analysis of Tb I hfs on a multi-configuration basis, based on the results of this work, yielded a value of the one-electron parameter as well as the respective radial integral , which can be compared with the values along the lanthanide elements series reported in the literature. More conclusive results can certainly be obtained once the experimental database for Tb I becomes more extensive.

Landé factor and lifetime measurements for odd-parity levels of Cr I by time-resolved laser spectroscopy

The Landé gJ factors of 35 levels, and the radiative lifetimes of 43 levels, of neutral chromium in the energy range 23 305.0026 to 53 782.78 cm−1 were measured by time-resolved laser-induced fluorescence and Zeeman quantum beat methods in laser-ablation plasma. Good agreements between the present results and the previous experimental values were achieved for both gJ factors and lifetimes. The measured gJ values are quite close to those calculated under the pure LS-coupling scheme. The lifetime values obtained are in the range 11.4 to 193 ns. To the best of our knowledge, 15 of the Landé factors and 17 of the lifetimes are reported for the first time.

Method for detecting the isomeric stateI=(3/2)+inTh229with laser-induced fluorescence

There are different predictions regarding the position of the isomeric state of $^{229m}\mathrm{Th}$. There is some question as to whether it even exists. We propose simple experiments to provide the evidence of the existence of this isomeric state. If the metastable isomeric state exists, we should be able to observe the effects of mixing of the nuclear wave functions of the ground state $I=5/2$ and the isomeric $I=3/2$ state via electronic shells. It will be shown as the differences between the hyperfine $A$ and $B$ constants, which will be measured by means of the laser-induced fluorescence methods and those predicted by semiempirical calculations. The wave function for the atomic state $|\mathrm{conf}.SLJIF\ensuremath{\rangle}$ contains contributions from both nuclear states $I=5/2$ and $3/2$, thus its effects on the hyperfine-structure patterns of spectral lines should be observed, confirming the existence of this isomeric state.

Laser induced fluorescence monitoring of the etching processes with the inward plasma

Laser induced fluorescence (LIF) spectroscopy has been used to monitor the etching processes in a localized plasma etching system. An inward plasma was employed for etching in which etching gas was discharged in the narrow gap between the etched sample and the entrance of an evacuating capillary tube. By observing the LIF spectrum, it was confirmed that the etch product SiF2 exists near the both Si and SiO2 sample surfaces being etched with CF4 inward plasma. The plasma gas temperature was estimated to be ∼400 K from the comparison of the LIF spectrum with the rotational simulation. LIF method was applied to the etching endpoint detection of two kinds of material, thermally-grown SiO2 on Si and spin-coated Polyimide Isoindoro Quinazorindione (PIQ) film on Si. The endpoint was detected from the onset of SiF2 production by the etching of Si substrate in the case of PIQ/Si. The signal intensity of SiF2 from the Si substrate during etching was several times larger than that from the SiO2 layer, and thus, the endpoint of SiO2 etching was detected by the abrupt increase of SiF2 signal. The etch rates of PIQ and SiO2 at the center of the capillary were determined to be 1.09 μm/min and 1.66 μm/min, respectively.

Hyperfine structure of the 4f85d6s2 configuration of the Tb atom

In this work, A and B hyperfine structure constants of electronic levels belonging to the configuration 4f85d6s2 of the terbium atom are presented, obtained via investigation of the hyperfine structure of 42 spectral lines, performed with the method of laser-induced fluorescence (LIF) in a hollow cathode discharge. Results for 14 of the investigated levels belonging to the configuration 4f85d6s2 were obtained for the first time. Also results concerning the hyperfine structure of 29 levels, involved in the transitions as upper levels, are presented. For these levels, almost all the results were obtained for the first time. On the basis of the results obtained within this work and those known from the literature, parametrization of the hyperfine structure was performed. The determined values of one-electron parameters for configuration 4f85d6s2 were compared to the values known from literature, determined so far on the basis of a much lower number of electronic levels. Values of relativistic radial integrals of the hyperfine structure for electrons 4f and 5d of the configuration 4f85d6s2 were calculated with the use of the MCDF code. The comparison of radial integrals calculated semi-empirically with those determined with MCDF method yielded an estimate of the values of configuration interaction parameters in the case of both magnetic dipole and electric quadrupole interactions of the terbium atom.

Comparison of Large Eddy Simulations and κ-ε Modelling of Fluid Velocity and Tracer Concentration in Impinging Jet Mixers

Abstract Simulations of turbulent mixing in two types of jet mixers were carried out using two CFD models, large eddy simulation and κ-ε model. Modelling approaches were compared with experimental data obtained by the application of particle image velocimetry and planar laser-induced fluorescence methods. Measured local microstructures of fluid velocity and inert tracer concentration can be used for direct validation of numerical simulations. Presented results show that for higher tested values of jet Reynolds number both models are in good agreement with the experiments. Differences between models were observed for lower Reynolds numbers when the effects of large scale inhomogeneity are important.

Characterization of Motor Oil by Laser-Induced Fluorescence

A new laser-induced fluorescence method is presented to classify brands of motor oil. A 266-nanometer radiation was employed to collect sixty sets of fluorescence spectra for each brand. Cluster analysis and support vector machine were employed to distinguish motor oils with principal component analysis, which was applied to extract spectral characteristics. The recognition accuracy was up to 100 percent. The results demonstrate that laser-induced fluorescence offers rapid response, high recognition, and high sensitivity for the classification of motor oils.

On-line molecular iodine isotopologue detection in gaseous media during spent nuclear fuel reprocessing using a laser-induced fluorescence method

The paper reports on on-line measurement of the 127I129I, and concentrations during spent nuclear fuel (SNF) reprocessing using a laser-induced fluorescence method. A He–Ne laser (632.8 nm) was used as a fluorescence excitation source. The detection limits obtained for molecular iodine isotopologue concentrations demonstrate the possibility of using this method for iodine control both in gaseous technological media generated during SNF reprocessing and after passing through the gas purification system (in atmosphere emission).

Effects of argon gas pressure on its metastable-state density in high-density plasmas

The effect of argon gas pressure on its metastable density in inductively coupled plasmas (ICPs) is investigated by using the laser-induced fluorescence method. Our results show that the metastable-state density of argon varies with the gas pressure depending on the measurement position; the density decreases with the pressure at a position far from the ICP antenna, whereas it increases with the pressure at a position near the antenna. This contrast in the metastable-state density trend with the pressure is explained by considering the electron temperature variations at the two measurement positions. The theoretical interpretation and calculation using a global model are also addressed in detail in this paper.

Radiative lifetimes and transition probabilities in Rh I

Radiative lifetimes of 17 high-lying excited states in Rh I aremeasured using the time-resolved laser-induced fluorescence method. Out of these lifetimes, 13 are new and the remaining four confirm previous measurements. Furthermore, we report the first theoretical investigation of Rh I, where the radiative decay properties of all experimentally known levels below 47 000 cm(-1) are calculated using a pseudo-relativistic Hartree-Fock method including core polarization effects. The theoretical calculations are found to be in very good agreement with the experimental results. A large set of new transition probabilities is presented for lines of astrophysical interest in the spectral range 2200-10 000 angstrom.

Active control of coaxial jet mixing with manipulation of primary vortical structures by arrayed micro flap actuators

Active mixing control of a methane/air isothermal coaxial jet was achieved using micro magnetic flap actuators arranged on the inner surface of the outer annular nozzle. The spatio-temporal evolution of vortical structures and the scalar mixing were studied through the particle image velocimetry and planar laser-induced fluorescence methods. In contrast to studies on jet control using acoustic forcing, the mechanical movement of the flap directly generated large-scale intense vortices. The mixing was enhanced significantly by the vortices formed in the inner shear layer, although the control input was given to the outer shear layer. It was found that the primary vortex rings dominated the near-field mixing, while streamwise vortices were responsible for the downstream mixing. It was also demonstrated that the radial range of the inner fuel transportation could be manipulated flexibly by adjusting the shedding interval of the vortices. Especially, the mixing was enhanced most significantly when the primary vortices were most densely populated near the nozzle exit at the control Strouhal number of unity.

Proposal and examination of method of water removal from gas diffusion layer by applying slanted microgrooves inside gas channel in separator to improve polymer electrolyte fuel cell performance

The objective of this study was to improve the management of moisture from the gas diffusion layer (GDL) in the gas channel of a separator for PEFC. At the cathode-side, oxygen is transported as reactant gas from gas channel through GDL. When large quantity of moisture is generated during high power generation, moisture blocks transport of oxygen, and the cell voltage drops drastically. Narrow microgrooves with axes at tilt angle to the air flow were arranged inside channel walls. The water from GDL was discharged along microgrooves to facing top of GDL by forces of capillary and air flow shearing. Laser induced fluorescence method was used to measure water velocity in microgrooves. The effect of air velocity in the gas channel on water velocity in microgrooves was investigated. It was shown microgrooves manufactured inside gas channel worked properly. Water velocity in microgrooves increased with increasing air velocity, and moisture could be discharged from GDL by applying microgrooves. Furthermore, effective length of the microgrooves needed to remove water from the GDL surface increased with decreasing inclination angle of microgrooves in the range of 20°–45°. An effective length of approximately 200 mm was attained, which was overall length of experimental apparatus.

H111 対向流プール燃焼を用いたエタノールの蒸発・燃焼過程に対する研究(一般講演(3))

For obtaining the data that contributes to propose detailed chemical reaction mechanism including the evaporation process of the liquid fuel, experimental study of counter-flow pool combustion was conducted. The one-dimensional diffusion flame was formed in this configuration. With respect to the counter-flow pool combustion of ethanol in this study, we carried out the temperature measurement by thermocouple and OH measurement by laser induced fluorescence method. The results obtained by the experiments were compared with the numerical simulation with OPPDIF/CHEMKIN-Pro. Results showed good agreement with experimental results and numerical results. In addition, we also tried numerical simulation of hydrazine as a realistic fuel.

Development of Ar I and Ar II Measuring System using Laser-Induced Fluorescence Methods in High-Density Helicon Plasma

Development of Ar I and Ar II Measuring System using Laser-Induced Fluorescence Methods in High-Density Helicon Plasma

Exploration of spontaneous vortex formation and intermittent behavior in ECR plasmas: The HYPER-I experiments

HYPER-I (High Density Plasma Experiment-I) is a linear device that combines a wide operation range of plasma production with flexible diagnostics. The plasmas are produced by the electron cyclotron resonance (ECR) heating with parallel injection of right-handed circularly polarized microwaves of 2.45 GHz from the high-field side. The maximum attainable electron density is more than two orders of magnitude higher than the cutoff density of ordinary waves. Spontaneous formation of a variety of large-scale flow structures, or vortices, has been observed in the HYPER-I plasmas. Flow-velocity field measurements using directional Langmuir probes (DLPs) and laser-induced fluorescence (LIF) method have clarified the physical processes behind such vortex formations. Recently, a new intermittent behavior of local electron temperature has also been observed. Statistical analysis of the floating potential changes has revealed that the phenomenon is characterized by a stationary Poisson process.

The matrix influence on the determination of low uranium concentrations by laser induced fluorescence method

A measurement technique enabling the determination of low uranium concentration utilizing system used for time resolved laser induced fluorescence spectroscopy (TRLFS), based on a commercially available kinetic phosphorescence analysis method has been developed. The effect of the matrix, complexing agent, and the level of acidification on the fluorescence spectra and integral intensity was studied. The method is highly influenced by the sample matrix; particularly if different starting uranium salts are in the calibration solutions and in the samples. In the initial study of these effects, TRLFS measurements have been used in order to clarify this behavior.

Flow structure formation in an ion-unmagnetized plasma: The HYPER-II experiments

The HYPER-II device has been constructed in Kyushu University to investigate the flow structure formation in an ion-unmagnetized plasma, which is an intermediate state of plasma and consists of unmagnetized ions and magnetized electrons. High density plasmas are produced by electron cyclotron resonance heating, and the flow field structure in an inhomogeneous magnetic field is investigated with a directional Langmuir probe method and a laser-induced fluorescence method. The experimental setup has been completed and the diagnostic systems have been installed to start the experiments. A set of coaxial electrodes will be introduced to control the azimuthal plasma rotation, and the effect of plasma rotation to generation of rectilinear flow structure will be studied. The HYPER-II experiments will clarify the overall flow structure in the inhomogeneous magnetic field and contribute to understanding characteristic feature of the intermediate state of plasma.