Accurate quantitative CF-LIBS analysis of both major and minor elements in alloys via iterative correction of plasma temperature and spectral intensity

The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes. A quantitative calibration-free laser-induced breakdown spectroscopy（CF-LIBS） analysis method, which carries out combined correction of plasma temperature and spectral intensity by using a secondorder iterative algorithm and two boundary standard samples, is proposed to realize accurate composition measurements. Experimental results show that, compared to conventional CF-LIBS analysis, the relative errors for major elements Cu and Zn and minor element Pb in the copperlead alloys has been reduced from 12%, 26% and 32% to 1.8%, 2.7% and 13.4%, respectively.The measurement accuracy for all elements has been improved substantially.

Influence of Plasma Temperature on the Concentration of NO Produced by Pulsed Arc Discharge

This study conducted experiments on producing inhaled medical nitric oxide （iNO） by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discharge, as well as the change of the ratio of NO2/NO under different discharge current were investigated. Through the analysis of plasma emission spectrum, the relationship between discharge current and arc plasma temperature was studied. The results indicate that, as discharge current increases, the arc plasma temperature increases, which then leads to the increase of NO concentration, the decrease of NO2 concentration, and the rapid decrease of the ratio of NO2/NO. When the plasma temperature is 9000 K, the ratio of NO2/NO is approximately 60%, while when the plasma temperature varies between 10550 K and 11300 K, the NO2/NO ratio is within the range of 4.2% to 4.6%.

Experimental Study on Plasma Temperature of Semiconductor Bridge

The plasma temperature of the semiconductor bridge (SCB) was measured in real-time according to relative intensity ratio of dual lines of atomic emission spectrum.The plasma temperature under different discharge pulses and the influence of discharge pulse energy on it were studied.The results show that the plasma peak temperature rises gradually with the increase of initial discharging voltage and charging capacitance.For the capacitance of 22 μF,if the initial discharging voltage increases from 21 V to 63 V,the plasma peak temperature rises from 2 000 K to 6 200 K.For the discharging voltage of 39 V,the peak temperature rises from 2 200 K to 3 800 K when the capacitance increases from 6.8 μF to 100 μF.The change of pulse discharge has a very small effect on the plasma temperature at the late time discharge (LTD).In view of the change of plasma temperature with the pulse energy,the discharging voltage has a greater effect on the plasma temperature than the capacitance.The results provide some experimental basis for the further research on SCB ignition and detonation mechanisms.

Study of plasma parameters of coaxial plasma source using triple Langmuir probe and Faraday cup diagnostics

Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma.The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are(1.6±0.5)×10^(19)m^(-3)and(2.8±0.6)×10^(19)m^(-3)for hydrogen and carbon plasma respectively and the peak temperature is 3.02±0.5 eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be 4.54±0.25 cm/μs and 1.81±0.18 cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.

Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

Nitric oxide （NO） is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide （NO2）, which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.

Femtosecond laser-induced Cu plasma spectra at different laser polarizations and sample temperatures

Laser-induced breakdown spectroscopy(LIBS) is a good technique for detecting and analyzing material elements due to the plasma emission produced by the high-power laser pulse. Currently, a significant topic of LIBS research is improving the emission intensity of LIBS. This study investigated the effect of laser-polarization on femtosecond laser-ablated Cu plasma spectra at different sample temperatures. The measured lines under circularly polarized lasers were higher than those under linearly and elliptically polarized lasers. The enhancement effect was evident at higher Cu temperatures when comparing the plasma spectra that have circular and linear polarizations for different target temperatures. To understand the influence of laser-polarization and sample temperature on signal intensity, we calculated the plasma temperature(PT)and electron density(ED). The change in PT and ED was consistent with the change in the atomic lines as the laser polarization was being adjusted. When raising the Cu temperature, the PT increased while the ED decreased. Raising the Cu temperature whilst adjusting the laser-polarization is effective for improving the signal of femtosecond LIBS compared to raising the initial sample temperature alone or only changing the laser polarization.

Influence of the position relationship between gas–liquid interface and laser focus on plasma evolution characteristics in jet LIBS technology

In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between laser focus and gas–liquid interface,this work takes the plasma generated by laser-induced liquid jets as the object of study and discusses the changes in the spatial and temporal evolution characteristics and spectral radiation of the plasma when the position parameters between the laser focal point and the gas–liquid interface are different.The initial breakdown position is always between the front interface and the focus when the laser focus moves along the vertical direction of the interface,forming a phenomenon like’interface effect’.The relationship between laser pulse energy and breakdown probability exhibits a law similar to a‘hysteresis curve’in the study of breakdown threshold.In this work,plasma with smaller size,rounder shape,stronger radiation,higher temperature,and higher density can be produced when the focus position is in the liquid column 0.2 mm away from the front interface.Simultaneously,the spectral signal intensity and signal-to-back ratio of the characteristic peaks of target elements in water reach maximum values,and the spectral signal becomes more stable(relative standard deviation value reaches 2%).The Ca element’s ion radiation at 393.366 nm and atomic radiation at 422.673 nm are studied using narrow-band filtering imaging and time-space resolution spectroscopy.The findings demonstrate that the laws of ion and atomic radiation are not perfectly consistent in space and time.

Applications and challenges of low temperature plasma in pharmaceutical field

Low temperature plasma(LTP)technology has shown an outstanding application value in the pharmaceutical filed in recent ten years.This paper reviews the research advances in LTP,including its effects on enhancing or inhibiting drug activity,its combined use with drugs to treat cancers,its effects on the improvement of drug delivery system,its use in preparation of new inactivated virus vaccines,its use with mass spectrometry for rapid detection of drug quality,and the anti-tumor and sterilization effects of plasma-activated liquids.The paper also analyzes the challenges of LTP in the pharmaceutical filed,hoping to promote related research.

Influence of sample temperature on the expansion dynamics of laser-induced germanium plasma

In this paper, we investigated the influence of sample temperature on the expansion dynamics and the optical emission spectroscopy of laser-induced plasma, and Ge was selected as the test sample. The target was heated from room temperature（22 °C） to 300 °C, and excited in atmospheric environment by using a Q-Switched Nd：YAG pulse laser with the wavelength of 1064 nm. To study the plasma expansion dynamics, we observed the plasma plume at different laser energies（5.0, 7.4 and 9.4 mJ）and different sample temperatures by using time-resolved image. We found that the heated target temperature could accelerate the expansion of plasma plume. Moreover, we also measured the effect of target temperature on the optical emission spectroscopy and signal-to-noise ratio.

Numerical Investigation on the Flow and Temperature Fields in an Inductively Coupled Plasma Reactor

This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.

Oxidation Degradation of Aqueous Carbofuran Induced by Low Temperature Plasma

The oxidative degradation of aqueous carbofuran, a heavily used toxic carbamate insecticide by low temperature plasma, was investigated. The results show that the treatment efficiency increases with the increase in initial concentration. Raising the treatment temperature and changing the pH value can result in enhanced degradation of carbofuran in solution. The results also show that low temperature plasma treatment can effectively remove chemical oxygen demand （COD） of carbofuran in the solution.

Effect of Treatment Temperature on Iron Nitride Foils Irradiated with Nitrogen Plasma

We investigated the effect of treatment temperature on the magnetic property of iron nitride foils irradiated with nitrogen plasma. The iron nitride foils irradiated with nitrogen plasma were composed of ε-Fe2/3N, γ'-Fe4N and γ nitrogen austenite in α-Fe of the matrix. The saturation magnetization of the iron nitride foils decreased with increasing the surface temperature. The coercive force of the iron nitride foils increased with increasing the surface temperature.

A STUDY ON THE STRUCTURE AND PROPERTIES OF POLYBUTYLALDEHYDE FORMED IN LOW TEMPERATURE PLASMA

The polybutylaldehyde obtained by plasma polymerization was investigated by means of IR, X-ray diffraction, GC-MS, elementary analysis, TEM, electron diffraction and contact angle measurements etc. The results showed that the polymer formed in plasma is amorphous crosslinked polymer, and its backbone is made of carbon atoms. The surface energy of the polymer film is independent of the polymerization conditions. No addition reaction has taken place in the carbonyl group of butylaldehyde in the plasma condition. The result of the wettability measurements showed that the polymer film is generally hydrophobic and the surface energy of the film is about 41 dyn/cm, in which the dispersion force contribution is the majority. The electron diffraction proved that some crystal substance, even the single crystals were present in the polymer. X-ray diffraction also proved the presence of crystal and showed about 15% crystaUinity fraction.

Deposition of Amorphous Carbon Films using ECR Plasma byVarying the Substrate Temperature

Amorphous hydrogenated carbon thin films have been deposited with benzene plasma in an electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition system. The characteristic of Benzene discharge plasma has been monitored by Mast spectrometry. It shows that the majority of the plasma species in the downstream ECR Plasma with benzene as gas source are acetylene, ethylene and higher mass species. In the experiments, the effects of the substrate temperature on the deposition rates have been emphatically studied. The structures of the films were analyzed by FTIR and Ramam spectrum.The results show that when the substrate temperature rises, the deposition rate drops down, the hydrogen Foment decreases, with the higher SP3 content being presented in the film.

Observation of Temperature Induced Plasma Frequency Shift in an Extremely Large Magnetoresistance Compound LaSb

We report an optical spectroscopy study on LaSb, a compound recently identified to exhibit extremely large magnetoresistance. Our optieal measurement indicates that the material has a low carrier density. More inter- estingly, the study reveals that the plasma frequency increases with decreasing temperature. This phenomenon suggests either an increase of the conducting carrier density or/and a decrease of the effective mass of carriers with decreasing temperature. We attribute it primarily to the latter effect. Two possible scenarios on its physical origin are examined and discussed. The study offers new insight into the electronic structure of this compound.

Diagnostics of electron temperature and ions distribution in expanding Al plasmas pumped by a ns-pulsed 1.06μm laser

Resonance lines are extensively used to diagnose electronic temperature Te and ions distribution. However, the analysis of the x-ray spectroscopy emitted from plasmas produced by a ns laser Jsually needs the help of a code or some assumptions. In this paper, a diagnostic idea of using line-pairs emitted from a doubly-excited state is proposed. By using the method presented in this paper, Te and the fractional population ratio of bare nuclei and H-like ions are directly obtained from the emission intensity ratios.

低温等离子治疗儿童鼻咽部第二鳃裂囊肿分析

目的探讨儿童鼻咽部第二鳃裂囊肿的临床特征和治疗方式,提高诊治能力。方法回顾性分析河北省儿童医院收治的4例儿童鼻咽部第二鳃裂囊肿的临床资料,包括年龄、性别、症状、影像学资料和治疗过程。总结分析病变部位特点,B超、CT或MRI特征,术后病理结果及治疗方式。结果4例鼻咽部第二鳃裂囊肿患儿均表现为鼻咽侧壁咽鼓管咽口与腭咽弓后上方连线上的囊性肿物,囊壁较厚,影像学检查结果均为囊性病变。4例患儿选择内镜下低温等离子病变切除术,其中2例为内侧囊壁大部分切除术,将囊腔充分敞开,2例为囊肿全部切除术。术后病理提示衬覆纤毛柱状上皮或复层上皮,周围淋巴组织增生。术后随访1.5~3年无复发。结论儿童鼻咽部第二鳃裂囊肿临床罕见,诊断主要依靠病变部位及术后病理结果,内镜下低温等离子切除病变组织是微创、安全、有效的治疗方式。

Atmospheric pressure plasma jet utilizing Ar and Ar/H_2O mixtures and its applications to bacteria inactivation

An atmospheric pressure plasma jet generated with Ar with H2O vapor is characterized and applied to inactivation of Bacillus subtilis spores. The emission spectra obtained from Ar/H2O plasma shows a higher intensity of OH radicals com- pared to pure argon at a specified H2O concentration. The gas temperature is estimated by comparing the simulated spectra of the OH band with experimental spectra. The excitation electron temperature is determined from the Boltzmann＇s plots and Stark broadening of the hydrogen Balmer H/3 line is applied to measure the electron density. The gas temperature, ex- citation electron temperature, and electron density of the plasma jet decrease with the increase of water vapor concentration at a fixed input voltage. The bacteria inactivation rate increases with the increase of OH generation reaching a maximum reduction at 2.6% （v/v） water vapor. Our results also show that the OH radicals generated by the Ar/H2O plasma jet only makes a limited contribution to spore inactivation and the shape change of the spores before and after plasma irradiation is discussed.

Time-Resolved Emission Spectroscopic Study of Laser-Induced Steel Plasmas

Laser-induced steel plasma is generated by focusing a Q-switched Nd：YAG visible laser（532 nm wavelength） with an irradiance of 1 x 109 W/cm2 on a steel sample in air at atmospheric pressure.An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions.Using time-resolved spectroscopic measurements of the plasma emissions,the temperature and electron number density of the steel plasma are determined for many times of the detector delay.The validity of the assumption by the spectroscopic methods that the laser-induced plasma（LIP） is optically thin and is also in local thermodynamic equilibrium（LTE） has been evaluated for many delay times.From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value,the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns,900 ns and 1000 ns.

Spatio-temporal evaluation of Zr plasma parameters in a single-beam-splitting double-pulse laser-induced plasma

The plasma shielding effect is one of the major weaknesses of laser-induced breakdown spectroscopy(LIBS)as it causes non-linearity in signal strength.Although LIBS is typically carried out in constant laser energy,this non-linearity causes a reduction in sensitivity.In this work,we systematically examine laser-induced plasma,formed by two different excitation source modes,i.e.single pulse(SP)-excitation and single-beam-splitting double-pulse(SBS-DP)-excitation over Zr-2.5%Nb alloy.The two most important plasma parameters influencing the emission line intensity,plasma temperature(Te)and electron density(Ne)were studied and compared for both modes of laser excitation.Comparison of the results conclusively demonstrates that due to the splitting of the laser energy in the SBS-DP mode,the plasma shielding effect is significantly reduced.The reduced plasma shielding translates to an increased laser–sample coupling under SBS-DP mode.Temporal imaging of the total intensity of the laser-induced plasma in both excitation modes was also studied.The study shows how the plasma shielding effect can be reduced to improve the analytical quality of the LIBS methodology.