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.     

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.     

Emission Spectrometric Analysis of Fresh Waters with U-Shaped D.C. Arc with Aerosol Supply

Abstract

The application of a U-shaped d.c. arc with aerosol supply for analysis of fresh waters has been described. Limits of detection obtained with d.c. plasma compare well with those reported for ICP. A number of spectral lines and molecular bands were examined and the most suitable are selected to ensure the best limits of detection or wide dynamic ranges. Limits of detection in ng ml^?1, given in the parenthesis, following the element symbol, are: Al(0.9), B(0.6), Ba(0.2), Be(0.15), Ca(0.05), Cd(3.5), Co(1.1), Cr(0.2), Fe(2.4), Ga(0.5), Hg(9.0), K(0.3), Li(0.008), Mg(0.4), Mn(0.3), Mo(0.7), Na(0.04), Ni(2.0), P(45), Pb(12), Si(9.0), Sr(0.04), Zn(1.3).     

发射光谱法对早期激光诱导铝合金等离子体诊断研究

对激光诱导等离子体参数进行诊断有多种方法,其中采用发射光谱法对其诊断是一种重要的方法。文中采用Nd∶YAG固态激光器,输出波长1 064 nm红外激光与铝合金样品相互作用,深入研究了铝合金等离子体产生早期(<1 μs)谱线轮廓、谱线强度、线背比、谱线半峰宽及位移等随时间演变规律。研究表明,激光与物质相互作用早期,电子数密度非常大,电子与离子及原子之间的相互作用非常强烈,谱线的Stark展宽效应非常明显,导致多重谱线重叠在一起,随时间演变,电子数密度及电子温度的降低,多重谱线的半峰宽越来越窄且谱线轮廓对称性越来越好。MgⅠ285.212 6 nm谱线强度早期逐渐增强,大约100 ns左右谱线强度达到最大值,然后谱线强度呈逐渐减小的趋势,这是由于等离子体产生早期,电子及离子占主导地位,故早期原子谱线强度较弱,随时间演变,电子与离子之间的复合,原子数密度逐渐增加,故原子谱线逐渐增强,达到最大值之后,由于等离子体激发温度的降低,故谱线强度逐渐减弱。以NIST波长位置为参考,等离子体产生的早期谱线发生了红移,连续背景强度随时间演变呈幂函数形式急剧递减,与之相反,谱线的连续背景强度与谱线强度相比,连续背景衰减的速度更为迅速,故导致谱线信背比随时间演变呈增大趋势,本研究对等离子体早期这些现象从理论角度进行了深入探讨。     

165—350nm同步辐射与壁稳氩弧光谱分布的比对

以合肥８００ＭｅＶ电子储存环同步辐射和壁稳氩弧作为初级标准光源，在１６５－３５０ｎｍ波段，标定了石英窗口氙灯的光谱分布，最大偏差为１１％，以石英窗口氘灯为传递标准光源，在紫外及真空紫外辐射区完成了同步辐射和壁稳氩弧两种基准之间的对比。     

光谱方法研究大气压氩气等离子体喷枪的放电特性

利用同轴介质阻挡放电喷枪,通过氩气的流动在大气压空气中产生了均匀的等离子体羽。等离子体羽沿气流方向较为均匀,但在喷嘴处为白色且亮度较高,远离喷嘴处为蓝色,亮度较低。研究了等离子体羽长度与外加电压幅值、驱动频率和气体流速的关系,气流小于4 L·min-1时等离子羽的长度随气流的增大而增大,而当气流大于4 L·min-1时长度随气流的增大而减小。当气流保持恒定时,等离子体羽的长度随外加电压幅值或驱动频率的增大而增大。结合气体放电理论以及分析湍流和平流对放电的影响,对等离子体羽长度随实验参数的变化进行了定性解释。光学方法研究发现在外加电压正半周期等离子羽有一个发光脉冲,而负半周期没有发光信号。同轴介质阻挡放电正半周期有两个发光脉冲,负半周期有一个发光脉冲。通过对该N₂现象的分析,为等离子体羽的产生机制提供了一种可能的解释。采集了同轴介质阻挡放电和等离子体羽的发射光谱,研究发现除等离子体羽存在明显的OH和N₂的发射谱线外,其发射光谱没有明显差别。利用光学发射谱N+₂第一负带系,对等离子体羽转动温度进行了测量,发现转动温度沿远离喷嘴的方向逐渐降低,且转动温度随电压幅值的增大而增大。     

光学发射光谱法测量氩气微空心阴极放电中特性参数

针对微空心阴极放电(MHCD)装置,通过在氩气中添加少量氮气,分析氮分子第一正带系N2(B3ΠgA3u+)发射光谱的方法测量了MHCD中的气体温度,通过氩气中混有的少量氢气,分析Hβ谱线Stark加宽得到电子数密度。研究表明,MHCD在极小的体积和很高的功率密度下维持放电,致使发生了明显的气体加热现象,气体温度可高于700 K,并且随着放电室压强和放电电流呈有规律的变化,具有较好的可控性,电子数密度的量级为1014～1015cm-3。通过对不同条件下等离子体特性参数的诊断和分析,得到了其量级和变化规律,对MHCD的广泛研究和应用提供了重要的实验数据和技术支持。     

大气压氩气针-板介质阻挡放电的光电诊断

利用针-板介质阻挡放电装置,在4 mm长的气隙中产生了大气压氩气射流等离子体。利用电学方法实现了对放电电流和电荷量的同时测量,并且对放电脉冲数和放电功率进行了研究;利用发射光谱法对放电等离子体进行了空间分辨测量,并根据ArⅠ696.54 nm的Stark展宽计算了等离子体的电子密度。结果发现:随着外加电压的增加,每个周期内的放电脉冲数增加,放电功率也增加。随着针头距离的增加,电子密度由2.94×1015cm-3逐渐减小到2.28×1015cm-3。实验结果表明:电场强度对放电脉冲数和电子密度的空间分布起重要作用。     

Investigation of the Anode Boundary Layer of an Atmospheric Pressure Argon Arc

This paper is concerned with the thermodynamic state of the plasma in the anode region of a high intensity arc. Spectrometric studies of the boundary layer in front of a plane anode perpendicular to the axis of a wall-stablized, high-intensity arc in argon atmosphere indicate substantial deviations from LTE. Data taken at distances of 0.5 to 2 mm from the anode surface are evaluated with two different but not entirely independent non-equilibrium data reduction techniques in order to obtain radial distributions of electron temperature and electron density. The electron temperature distribution displays an off-axis peak which increases in magnitude with decreasing distance from the anode. Both electron temperatures and electron densities are considerably higher than the corresponding LTE values.     

Spectroscopic Diagnostics of Atmospheric Argon Microwave Plasma Based on an Inductive Coupling Window-Rectangular Resonator

We present a novel microwave plasma source based on an inductive coupling window-rectangular resonator. A definite volume of atmospheric argon microwave plasma is excited in the source under the input of several kilowatts of microwave power operating at 2.45 0Hz. The excitation temperature and electron temperature of the argon plasma are separately researched by using Boltzmann plot and line-to continuum intensity ratio of Ar I spectral lines. Its electron density is inferred from the Stark broadening of the Hβ line at 486.13nm.     

大气压直流氩等离子体光谱诊断研究

通过光谱诊断系统测量了大气压直流氩等离子体射流在弧室内和弧室出口的发射光谱,利用波尔兹曼曲线斜率法计算了射流的电子温度,根据Ar Ⅰ谱线的斯塔克展宽得到射流的电子密度,并对氩等离子体射流满足局域热力学平衡(LTE)状态的判定标准进行了分析,结果表明在文章的实验条件下大气压直流氩等离子体射流达到局域热力学平衡。     

The Study on the Arc Plasma Temperature Measurement by Optical Emission Spectroscopy with Fiber Optical Transmission

Abstract

A method for transmitting radiation of the arc plasma with multimode fused quartz fiber onto the spectrograph has been studied. The plot of the Boltzmann function in emission spectral analysis is used for measuring temperature of the arc plasma. The measured temperature of the arc plasma is 5946.6K from least square linear regression of ln[λI/(gA)] and E_i for a number of the emission line intensities of the excited copper atom. Its regression coefficient and measured precision are ?0.97% and 1.7%, respectively. The advantages of the method of the diagnostic temperature for the arc plasma are absolute measurements of the temperature, remote sensing, precision and suitable for mal-environment, such as high temperature, toxic, explosion, strong magnetic or/and electrical fields.

In addition, we have discussed the effect of the spectroscopic constants, such as transition probability, A , the statistical weight of the upper level, g , and the energy of the upper level, E_i , of copper lines on calculating temperature with a plot of the Boltzmann function in detail. The results show that the accurate measurement of the temperature for the arc plasma is obtained only when the spectroscopic constants are selected correctly.     

Optical Emission Spectroscopy Used to Study the Characteristics of the Capacitive Radio-Frequency Discharge in Argon

Capacitively coupled radio-frequency (13.56 MHz) glow discharge in argon at low pressure (200 mTorr) has been studied by optical emission spectroscopy (OES) and electrical probe. Increasing power density resulted in lowering of the electron temperature T _e and increase of the electron density n _e. The to transition in this case takes place smoothly. The intensity (I _750.4) of the emission line at 750.4 nm due to 2p₁1s₂ transition closely follows the variation of n _e with power density. Calculation of the electron-energy probability function shows that electron occupation mainly changes in the high-energy tail, which explains close resemblance of I _750.4 to n _e. At moderate pressures, only OES method was applied to observe - transition which is abrupt in this pressure range.     

Thermal Nonequilibrium of a Free-Burning Argon Arc Plasma

The axial distributions of the electron temperature and number density of a free-burning atmospheric argon arc plasma at 15 Amps have been measured using a Thomson scattering technique. In addition, the excitation temperature of singly ionized argon has been found spectroscopically by relative line intensity method. The results are presented in terms of the degree of electron temperature nonequilibrium as compared with the calculated Saha equilibrium temperature and with the measured ionic excitation temperature along the axis of the arc. The observed temperatures are discussed with respect to the theoretical ion-like particle temperature and to the effect of electrode geometry.     

A Power Interruption Technique for Investigation of Temperature Difference in Stabilized Low Direct-Current Arc Burning in Pure Argon on Atmospheric Pressure

Plasma of argon stabilized arc column, in a current range 3-11 A, is investigated using emission spectrometric diagnostic techniques. Temperatures are evaluated using several methods： argon line to adjacent recombinational continuum intensity ratio, absolute emissivity of argon line, measurement of electron number density, and power interruption. Electron number density is evaluated from absolute emissivity of recombinational continuum. The difference between electron Te and heavy particle Th temperature ranged from 4500 K for 3 A to 2300 K for 11A arc current. By comparing the present with the previously obtained results, using the same arc device but with the introduction of water aerosol, it is concluded that water aerosol reduces the difference Te - Th and brings plasma closer to the partial thermodynamic equilibrium state.     

发射光谱研究氩气/空气混合气体介质阻挡放电能量传递过程

使用水电极介质阻挡放电装置,对比氩气与氩气/少量空气的混合气体以及空气与空气/少量氩气的混合气体放电的发射光谱,研究了氩气与空气相混合时气体放电中的能量传递过程。实验发现, 当氩气中加入少量的空气时,氩原子谱线均变弱,说明空气中的氮分子对氩原子的各激发态具有猝灭作用。并且随着空气含量的增加,各谱线变弱的速率不同。越是与氮分子的激发电位接近的氩原子的激发态被猝灭的作用越明显。另一方面,当空气中加入少量氩气时,发现氮分子第二正带系和氮分子离子第一负带系的谱线均被增强。说明在空气/少量氩气放电中,氮分子的激发由于亚稳态氩原子的潘宁激发传能而增强。因此在氩气/空气混合气体放电中,气体成分及比例影响放电的发光特性和能量传输特性。     

等离子体电子温度的发射光谱法诊断

电子温度是表征等离子体性质的一个重要参数。由于等离子体放电过程非常复杂,要实时准确测定其电子温度值非常困难。发射光谱法作为一种等离子体诊断技术,因其所使用的仪器相对简单,并采用非接触测量,灵敏度高,响应速度快,可广泛地应用于各种等离子体性质的研究和参数的诊断。文章介绍了测定等离子体电子温度的双谱线法、多谱线斜率法、等电子谱线法、Saha-Boltzmann法、谱线绝对强度法等多种发射光谱法,同时综述了这些方法在等离子体电子温度诊断中的应用,旨在为实际过程中选择合适的等离子体诊断方法提供参考。     

Diagnostics of Electron Beams Based on Cherenkov Radiation in an Optical Fiber

Russian Physics Journal - The use of an optical fiber in which Cherenkov radiation is generated instead of a metal wire for scanning a beam profile allows a compact and noise-proof device for...     

基于光谱诊断的氩-氮P-TIG焊引弧的动态电弧物理特性研究

焊接电弧等离子体的物理特性直接决定了焊接接头的成形形貌,分析双组分保护气体的脉冲钨极惰性气体保护焊（P-TIG）动态电弧物理特性,为深入开展混合气体保护焊的焊缝成形物理过程研究提供理论基础。氩-氮混合气体保护焊电弧具有高热特性可以增加熔深,但在焊接前混合均匀的保护气体,引弧后气体浓度会重新分布,使电弧等离子体物理特性的实时动态变化特点变得复杂。光谱诊断是电弧等离子体物理特性测量的最重要手段,但对双组分气体保护的P-TIG焊电弧特性的研究仍需深入进行,特别是对于易引起缺陷的起弧过程,其动态物理特性亟需深入分析。针对氩-氮混合气体P-TIG焊的引弧过程,以P-TIG焊产生的氩-氮双组分电弧等离子体为研究对象,提出利用窄带滤光片与CCD相结合的高速摄影实验系统采集双组分电弧等离子的动态光谱信息,获取特征谱Ar Ⅰ 794.8 nm和N Ⅰ 904.6 nm的P-TIG焊电弧光谱强度动态分布;提出利用双元素双组分标准温度法计算P-TIG焊引弧过程中距离钨极下方1,2,3和4 mm位置处电弧等离子体的动态温度及浓度,定量分析80%Ar+20%N₂保护的P-TIG焊从引弧至电弧稳定过程的电弧等离子体物理特性实时分布。实验结果表明,80%Ar+20%N₂保护的P-TIG焊电弧强度、电弧温度及浓度的变化均与脉冲电流的变化同步,焊接电流在3 ms内达到稳定状态,而电弧等离子体的强度、温度及浓度需要更长时间达到平衡状态。从起弧到电弧等离子稳定燃烧的过程中,基值期间和峰值期间的电弧等离子体强度均呈现先升高再降低的趋势;由于阴极的热传导及电流密度的变化,使得电弧等离子体轴向位置的峰值温度及基值温度均出现迅速升高再缓慢降低的现象;由于粒子间碰撞及摩擦力的影响,使得电弧等离子体的峰值及基值期间氩的浓度均呈迅速减小再缓慢增加的趋势,且氩的浓度均低于焊前浓度。     

大气压中频氩∕丙酮等离子体发射光谱诊断

目前, 等离子体发射光谱应用于中频丙酮等离子体的研究鲜有报道。自建大气压氩∕丙酮喷射中频交流放电等离子体装置, 采用HR2000光纤光栅光谱仪对放电光谱进行记录, 并对实验中的光谱信号进行分析诊断。研究结果说明, 对大气压环境下, 使用氩气为“载气”, 对可挥发有机溶剂进行等离子发射光谱分析是一种可行的技术; 大气压下丙酮等离子体的活性成分和真空环境下丙酮等离子体产生的活性成分有很大区别, 氧元素对两种气压下等离子体活性成分有很大改变; 这种诊断方法对大气压下挥发性有机试剂的等离子体化学反应原理的研究, 有重要的指导意义。此外, 文中展示了大气压下丙酮沉积膜在两种光源下的形貌图, 结果说明在一定实验条件下得到了连续的沉积膜。