Multicomponent Thermal Plasma of Arc Discharges

This paper deals with investigations of thermal electric arc plasma in complex gas - metal vapour mixtures. Experimental techniques in the diagnostic were widely discussed. The study of non-steady-state discharges was performed with an appropriate temporal and spatial resolution. Spectroscopy investigations of plasma parameters in some modes of discharge operation were carried out. Spatial profiles of temperatures and electron densities were obtained. Plasma composition was calculated in an assumption of the local thermodynamic equilibrium. The influence of some mechanisms on plasma condition was analysed.     

Parameters of the Plasma of the Argon Arc Used to Deposit Coatings

We consider an argon d.c. arc in the device devised by us for depositing metallurgical coatings. The temperature and concentration fields of electrons needed to construct the quantitative model of heating of particles in a plasma stream are determined by spectroscopic methods.     

活性剂等离子弧焊焊接电弧的光谱与热分析

针对活性剂等离子弧焊焊接过程,利用光谱分析方法对活性剂等离子弧焊焊接电弧进行光谱分析,采用红外热像伪着色法测定活性剂等离子弧焊焊接电弧温度场,并建立活性剂等离子弧焊焊接电弧热流密度径向分布模型,对焊接电弧的成分及焊接电弧温度场进行了研究。研究结果表明,常规等离子焊焊接电弧以氩原子和氩一次电离离子的谱线为主,金属蒸气谱线不突出,焊接电弧以气体粒子为主,属于气体电弧;活性剂等离子弧焊焊接电弧的光谱中氩原子及氩一次离子谱线的辐射强度增强,Ti,Cr,Fe金属谱线大量涌现;活性剂等离子弧焊焊接电弧的温度分布比较紧凑,温度场外形窄,温度分布范围较集中,电弧径向温度梯度较大;电弧径向温度分布呈现正态Gauss分布模式。     

Spectroscopic Investigation of Plasma Composition of U-Shaped Argon Stabilized D.C. Arc

The spectroscopic analysis of emitted radiation from the U-shaped argon stabilized d.c. arc is performed when the arc was burning without and in the presence of water aerosol. The special attention is paid to the emission of molecular components. The radial distribution of rotational temperature is obtained from the OH band spectra. The arc plasma composition is also theoretically calculated supposing the state of local thermodynamic equilibrium and compared with experimental results.     

Emission of Ions from a Nonequilibrium Plasma

A model of a plasma ion emitter is considered for two types of velocity distribution of plasma electrons: the sum of two Maxwellian velocity distributions with different temperatures and the sum of a Maxwellian distribution and a directed flux. Criteria for the formation of a plasma emission surface are derived. The effect of the parameters of the electron distribution on the magnitude of the perturbation of the quasi-neutral emitting plasma by the external electric field of the negative electrode and on the emission current density is considered. A comparison with the Bohm case is performed.     

Optical Emission from a Low-Density Argon Plasma

In many laboratory experiments, the plasma parameters do not satisfy the requirements of the various theoretical radiation models that are needed for spectral plasma diagnostics. We report here a coaxial system from which we determine the empirical relationship between the electron number density of a low-pressure argon plasma and the intensity of atomic line emission. This system is unique in that it allows the concurrent determination of electron number density and line emission intensity at various locations in the plasma. Dependence of emission intensity on the neutral background pressure and the strength of the microwave pulse, which generates the plasma, suggests that the steady-state corona model is relevant for this system.     

Application of Thermal Plasma Arc Melting for Critical Alloy Ingot Preparation

Volatile foreign dependence, cyclic availability, and restricted critical material stockpiles have focused considerable attention on the feasibility of new and more efficient processing/ recycling schemes. Over the past several years United Technologies Research Center (UTRC) has been investigating plasma processing techniques for the reprocessing and upgrading of critical materials and alloys. As part of this effort, a laboratory scale dc thermal plasma reactor operating in the transferred mode was developed and successfully demonstrated. The reactor was originally developed for recycling MCrAlY and Ni alloy materials and more recently modified for processing titanium (Ti) alloys. The reactor demonstrated the ability to produce homogeneous void-free 5-cm-diameter ingots in an inert atmospheric pressure environment without loss of volatile alloy constituents and with no significant contamination introduction. Exploratory experiments were also conducted to investigate the effectiveness of this type of plasma reactor for reducing the surface oxygen contamination of the Ti alloy feed material, as generated during high-speed machining operations. The process is based on high-reactivity atomic hydrogen species generated in the plasma region for reducing the oxygenated titanium surface compounds (measured to be predominantly TiO2). Only modest oxygen reductions were achieved. Aspects of this research and development will be described in this paper.     

Rotational Temperatures Determined from C2 Molecular Band Spectra in a Thermal Argon Plasma Interacting with Insulating Materials

The interaction between argon plasma and an insulating material is studied in an arc chamber. Argon plasma is put in contact with insulator by means of a magnetic field produced by Helmoltz coils. Arc spectrum is analysed by means of an optical multichannel analyser (O.M.A) connected to a monochromator and a Personal Computer.

The spectral analysis shows, for each insulator, the molecular spectrum of C₂ Swan system (d³ P_g,v' = 0-> a ³P_u,v'' = 0) with head band at 516,52 nm.

The rotational temperature is determined from the slope calculation of the Boltzmann plot.     

直流氩等离子体射流电子温度的测量

直流等离子体射流的电子激发温度,是等离子体射流物理特性中的一个非常重要的参数,并且影响着射流中其他众多特征参数。文章采用发射光谱诊断技术对直流氩等离子体射流进行实验研究,对实验所测得的射流的光谱强度信号进行分析,并采用玻尔兹曼曲线斜率法计算等离子体射流的激发温度。实验结果表明,等离子体射流的激发温度在等离子体发生器的轴向上的分布,随着离出口的距离增大,激发温度显著地下降。并且激发温度受电流和流量的影响较大,提高电源的输出电流,或者增加氩气的流量,激发温度都会升高。     

Temperature Determination from the Continuous Emission of a Dense Argon Plasma

The temperature of the laser sustained plasma has been determined from the continuum emission coefficient at different wavelengths. The experiments were performed in an argon plasma at the pressure of 10 atm. The spurious continuum resulting from merging of spectral lines was investigated numerically. Its influence on the measured emission coefficient in the red region has been found to be considerable.     

Analytical Models of Free-Burning Electric Arcs

Two-dimensional electric arc model based on the solution of the energy equation by means of variables separation method in curve-line orthogonal coordinates, associated with electrical arc characteristics, is suggested. Quite accurate solution of MGD-equations complete system for the arc with radial current spreading out of the top nozzle of the conic electrode is produced. Influence of electrode geometry on arc column characteristics in some particular cases has been analysed.     

The Rotation of Ions and Neutrals in a Cylindrical Magnetized Hollow Cathode Argon Arc

In a magnetized hollow cathode arc rotational velocities of ions and neutrals and their temperatures were measured in axial and radial dependence. In comparison with theory experimental results give a detailed analysis of radial transport phenomena.     

Non-LTE Argon Plasma Composition at Atmospheric Pressure

The knowledge of plasma composition is very important for various plasma applications and the prediction of other plasma properties. Most of the plasma currently used in plasma-aided processing is in the non-LTE (Local Thermodynamic Equilibrium) state. In this paper, the Saha equations, Debye-length equation, lowering-of-ionization-energy equation and pressure-correction equation, used to calculated the non-LTE plasma composition, are analyzed. The recently published theoretical results are compared with experimental data.     

激光诱导氩气等离子体时间分辨特性研究

激光诱导击穿光谱(L IB S)以激光诱导微等离子体的原子发射为技术特征,在科研与工业领域正得到重视与蓬勃发展.作为环境气体的氩气对等离子体演化过程中粒子的碰撞过程有重要影响,决定着L IBS技术分析性能的发挥.利用光谱诊断技术深入研究LIBS技术条件下氩气的光谱特征,对于提升LIBS技术及其应用水平具有重要的意义.利...     

Electrical and Optical Properties of High-Pressure Argon Plasma

Argon plasma has been investigated in the pressure range p ? 200 bar and at temperatures up to 13 000 K. The experiments were performed by using a wall-stabilized arc in an uncooled copper cascade. The measured electrical conductivity agrees with theoretical predictions based on the unified theory. Line and continuous intensities, as well as width and shift of the Ar I line at ? = 696.5 nm, were determined. A set of optimized atomic constants for these radiative processes was obtained by a newly developed multiple approximation method. While linewidth due to Stark and Van der Waals broadening are in fair agreement with theory, the line shift has to be corrected.     

Laboratory Observation of a Very Low Frequency Instability in an Argon Plasma

Very low frequency (50 to 500 Hz) self-excited electrostatic waves are detected in a cylindrical argon plasma column with a weak axial magnetic field (10 to 100 G). The waves propagate azimuthally with a phase velocity in the electron diamagnetic drift direction, but with a speed at least an order of magnitude less than the ion acoustic speed. A number of known plasma instabilities are considered as possible explanations, though most of them do not seem to account for the observed characteristics of the waves.     

Temporal Evolution of Excited Level Populations in a High-Velocity Argon Plasma Flow

A simplified collisional-radiative model is applied to a high velocity plasma flow through the arcjet nozzle to investigate the temporal evolution of excited level population densities in the selected spatial positions inside arcjet thruster. Oomputations are carried out for various sets of input parameters such as electron temperature, electron number density, atom temperature, and pressure. The numerical results illustrate that the exter~t of the ionization-recombination non-equilibrium is strongly dependent on the electron temperature and pressure, and is significantly affected by resonance radiation.