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Determination of Major Inorganic Nutrients in Maize Tissues by Calibration-Free Laser Induced Breakdown Spectroscopy
摘要： The quality of the available food is the main issue in the developing countries and maize is one of the commonly used foodstuffs in these countries. Laser-induced breakdown spectroscopy (LIBS) was employed to characterize the presence of the major inorganic nutrients in the maize samples. Each of the samples was shown to contain following elements: K, Ca, Mg, Fe, Na, Si, Li, Sr, Ti, Al, and C while Cr was only detected in the seeds. The electron number density was evaluated by the use of the Stark broadened profile of calcium line and the plasma temperatures have been determined using the Boltzmann plot method. Calibration-free LIBS (CF-LIBS) has been used for the quantitative elemental analysis of the samples. The consistency of the concentrations determined by CF-LIBS was validated using inductively coupled plasma – optical emission spectroscopy (ICP-OES).
关键词： calibration-free laser–induced breakdown spectroscopy (CF-LIBS),Maize,Plasma parameters,inductively coupled plasma–optical emission spectroscopy (ICP-OES)
更新于2025-09-12 10:27:22
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Spatial confinement of laser-induced plasma by laser-induced and obstacle-reflected shock wave and its effect on optical emission of laser-induced plasma
摘要： The laser-induced plasma (LIP) and the shock wave generated by pulsed laser ablation of a graphite target in air and reflected by a flat obstacle were examined by optical emission spectroscopy and probe beam deflection measurements. The interaction between the LIP and the shock wave and its effects on the expansion of the LIP as well as on the optical emission of carbon atoms were studied. The carbon atomic emission can be enhanced or reduced in the situation with a flat obstacle standing in the propagation path of the shock wave. The enhancement or reduction of the carbon atomic emission has a close connection with the shock wave generated by graphite ablation and reflected by the obstacle. The reflected shock wave confines the expansion of the LIP and impedes the travelling of the plasma species. The enhancement was observed at the detection position close to the target and with a short block-target distance. The shock wave thus reflected encounters the luminous LIP at its early expanding stage and confines the expansion of the LIP, resulting in the enhancement in the optical emission of carbon atoms. But at the detection position far from the target and with a longer block-target distance, a reduction in the optical emission due to spatial confinement was observed. The possible mechanisms responsible for the effects of spatial confinement on the optical emission were discussed.
关键词： laser-induced plasma,spatial confinement,optical emission spectroscopy,shock wave,probe beam deflection
更新于2025-09-12 10:27:22
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Investigation on plasma characteristics in a laser ablation pulsed plasma thruster by optical emission spectroscopy
摘要： In order to further improve the propulsion performance of pulsed plasma thrusters for space micro propulsion, a novel laser ablation pulsed plasma thruster is proposed, which separated the laser ablation and electromagnetic acceleration. Optical emission spectroscopy is utilized to investigate the plasma characteristics in the thruster. The spectral lines at different times, positions and discharge intensities are experimentally recorded, and the plasma characteristics in the discharge channel are concluded through analyzing the variation of spectral lines. With the discharge energy of 24 J, laser energy of 0.6 J and the use of aluminum propellant, the specific impulse and thrust efficiency reach 6808 s and 70.6%, respectively.
关键词： plasma,optical emission spectroscopy,propulsion performance,laser ablation pulsed plasma thruster
更新于2025-09-11 14:15:04
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Complementary Characterization of Laser-Induced Plasmas by Optical Emission Spectroscopy and Triple Langmuir Probe
摘要： In this article, we study the temporal evolution of the electron density and temperature of carbon laser-produced plasmas (LPP) using a combination of optical emission spectroscopy (OES) and the triple Langmuir probe (TLP) method. OES has been widely used to characterize LPPs but it is limited to distances relatively close to the target. On the other hand, the main advantage of TLP over the single-probe method is that it allows to obtain simultaneous measurements of electron temperature (Te) and density (Ne), without any voltage sweeping. In this article, we compare both techniques; measurements by OES were performed at distances from the target <1 cm, whereas the triple probe was employed for distances >5 cm. The plasma was generated by focusing nanosecond laser pulses onto a high purity graphite target placed inside a vacuum chamber. Our results show that the values of Te measured using both techniques predict decreasing exponential behavior. Ne determined by the spectral line Stark broadening in OES (<1 cm) was two orders of magnitude larger than that measured by the TLP (>5 cm). This difference in the electron density can be explained by radiative recombination and the presence of different kinds of plasma species detected by the TLP technique. The results show that both methods are complementary and their combination can be used to characterize LPP in a wide range of distances and timescales.
关键词： triple Langmuir probe (TLP),optical emission spectroscopy (OES),Laser-induced plasmas
更新于2025-09-11 14:15:04
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Measurement of Argon emission spectral of ICP plasma using a diagnostic system based on photomultiplier tubes array
摘要： Optical emission spectroscopy (OES) is one of the most important diagnostic tools in plasma physics. A self-built spectroscopic diagnostic system, owning temporal and spatial resolution, has been constructed using photo multiplier tubes (PMTs) array, spectrometer and other parts. The problem of superposition between inlet plane of bundle fiber and the focal plane of the spectrometer is analyzed and solved. In addition, the synchronization regulation of output of PMTs has been completed. This system is installed on an inductively coupled (ICP) plasma chamber in order to study the Argon (Ar) emission spectrum generated from typical radio frequency (RF) and pulse discharges. The test results show that the intensity of Ar emission spectrum increases with the power and pressure, but increase less with the flow and current ratio. Under pulse discharge condition, the intensity of spectrum does not change with the frequency, neither does the broadening of spectrum with time.
关键词： PMTs array,ICP plasma,Argon emission spectrum,Optical emission spectroscopy,RF and pulse discharges
更新于2025-09-10 09:29:36
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In situ measurement of the spectral reflectance of mirror-like metallic surfaces during plasma exposition
摘要： Visible spectroscopy in fusion plasmas crucially depends on the optical properties of first mirrors withstanding a considerable amount of radiation and particle fluxes. As a result of this interaction the optical properties of the mirrors could be changed so that a cleaning of the mirror is regularly required. Thus the reflectance of the first mirror must be monitored in situ. The newly developed Doppler-Shifted Reflectance Measurement (DSRM) diagnostic provides the spectral reflectance of mirrors in the absence of any calibration sources. It is based on the emission of fast H/D atoms in a low density Ar-H plasma by applying a negative potential on the order of to the mirror surface. Until now, the experimental data were restricted to measure only the fast atoms emission at the Hα line. In this work we prove that the new technique also provides the mirror reflectance at the Hβ line (Cu) (486 nm) relevant for the charge-exchange recombination spectroscopy (CXRS) measurements of the He II line (468 nm) in ITER. Moreover, the DSRM diagnostic remains sensitive to the polarization of the reflected light of a W mirror. We present the first experimental data on the time-dependent regime of operation: in situ monitoring of the degradation of an Al mirror is shown as a function of the mirror temperature. The passive heating of the mirror was performed by the plasma itself, which makes the separation between the impact of high temperature and plasma erosion on the mirror reflectance for the temperatures above 500 K impossible. A very good agreement of the experimental and the theoretical data calculated using the Drude theory for the temperature below 500 K is found. For the temperatures above 500 K the degradation of the reflectance of the mirror is determined by the erosion of Al, which is confirmed by monitoring the Al I spectral lines in unison.
关键词： light polarization,CXRS,surface degradation,optical emission spectroscopy,fast neutral atoms,spectral reflectance
更新于2025-09-10 09:29:36
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Experimental investigation on the optical emission spectroscopy of dielectric barrier discharge plasma actuators at different atmospheric pressures
摘要： The experiment of dielectric barrier discharge (DBD) plasma actuator using an asymmetrical electrodes configuration is conducted to investigate optical emission spectroscopy of the plasma discharge at pressures from 0.02 to 0.1 Mpa in air mixed with various concentrations of Ar (0%, 20%, 50%, and 80%). The measurements were performed with a sinusoidal driven DBD having an amplitude of 12 kV and a frequency of 1 kHz. The diffuse DBD discharge images and the optical emission spectra are recorded successfully, and the effects of pressure and concentration of Ar are investigated, respectively. It is found that the emission intensities of air discharge increase with decreasing the pressure but increasing the concentration of Ar to some extent. Especially, when the pressure is lower than 0.04 Mpa or the concentration of Ar is over 50%, the emission intensities increase obviously rapidly. The experimental results indicate that the low pressure environment and the high concentration of Ar are beneficial to improve the performance of the DBD plasma discharge actuators.
关键词： atmospheric pressure,plasma actuator,optical emission spectroscopy,dielectric barrier discharge,Ar concentration
更新于2025-09-09 09:28:46
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Optical emission spectroscopy investigation of the current sheet in a small-bore parallel-plate electromagnetic plasma accelerator
摘要： The optical emission spectrum of the propagating current sheet in a small-bore parallel-plate electromagnetic plasma accelerator has been studied. The accelerator is powered by a fourteen stage pulse forming network, which yields a damped oscillation square wave of current with a pulse width of 20.5 ls. The movement of the first current sheet and the second current sheet is identified using three single magnetic probes placed at various axial positions. Current sheet canting is measured by two double magnetic probes. The spectrum of the current sheet is measured using a spectroscopic system. The electron density of the current sheet plasma is determined via Stark broadening of the hydrogen Ha line. The current sheet is almost perpendicular to the electrode. The current sheet electron density increases as the current sheet propagates. The current sheet electron density is mainly determined by the prefill pressure rather than the discharge current. The impurity charged particles caused by ablation of the back wall insulator exists in the current sheet. Residual particles are generally left behind the first current sheet and are swept and ionized by the second current sheet. The estimated current sheet sweeping efficiency is greater than 80%. The parallel-plate electromagnetic plasma accelerator developed in this paper shows great potential in generating high electron density plasma jets.
关键词： Stark broadening,optical emission spectroscopy,parallel-plate electromagnetic plasma accelerator,current sheet,electron density
更新于2025-09-09 09:28:46
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Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD
摘要： The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.
关键词： Real time spectroscopic ellipsometry,Microcrystalline silicon,High rate deposition,Optical emission spectrum,Growth mechanism
更新于2025-09-09 09:28:46
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Blue-Emitting CsPbCl <sub/>3</sub> Nanocrystals: Impact of Surface Passivation for Unprecedented Enhancement and Loss of Optical Emission
摘要： High-energy-emitting CsPbCl3 nanocrystals have shown significant loss and enhancement of their emission intensity (～40?50 folds) during purification and surface treatments, respectively. This confirms that the surfaces of these nanocrystals are very sensitive. In this Letter, physical insights of the interface bindings on the surface of these blue-emitting CsPbCl3 nanocrystals with different passivating agents and their impact on purification are investigated. Using various metal chlorides consequential irrespective of the charge and size of the metal ions, metal acetates, and nonmetal chloride, the predominant influence of chloride ions in helping retrieve/intensify the blue emission is established. The purification processes are observed to be very delicate, and successive purifications with introduction of polar nonsolvents led to the transformation of an emitting cubic CsPbCl3 phase to nonemitting tetragonal CsPb2Cl5 phase nanocrystals irreversibly. The impact of various salt additions only temporarily helped in enhancing the emission, but the phase change remained inevitable upon successive purification. However, as a remedy, by in situ use of alkylammonium chloride salt in high-temperature reactions, the surface binding was improved, and significant emission as well as the phase could be retained with successive purifications.
关键词： surface passivation,purification,optical emission,CsPbCl3 nanocrystals,blue-emitting
更新于2025-09-09 09:28:46