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。     

不同时空结构的四边形放电斑图等离子体参量研究

采用发射光谱法,研究了不同时空结构四边形斑图的等离子体参量。实验发现,在低气压区和高气压区,四边形斑图表现出不同的时空结构。利用N₂分子第二正带系的六条谱线强度计算了分子振动温度;利用第一负带系N+₂(391.4 nm)与第二正带系N₂(394.1 nm)谱线强度比,研究了电子能量的变化;利用Ar原子696.54 nm谱线的展宽和频移来反映电子密度;利用Ar原子特征谱线强度比法计算了电子激发温度。结果表明：低气压区四边形斑图的分子振动温度、电子激发温度和电子平均能量均大于高气压区四边形斑图,而电子密度小于高气压区四边形的电子密度。     

大气压下石英毛细管内氩等离子体放电的发射光谱诊断

在长度为20 cm的石英毛细管内利用两个边缘锋利的中空的针型电极之间的氩气放电产生了高电子密度的大气压等离子体。利用发射光谱对所获得的等离子体的几个重要参数进行了诊断。利用计算机谱线拟合法合成了300 nm附近OH(A-X)的(0-0)转动谱带并通过与测量谱线的比较确定了等离子体的气体温度,根据H_β谱线Stark展宽法计算了等离子体的电子密度,采用玻尔兹曼曲线斜率法依据测得的有关氩的发射光谱估算了等离子体的电子温度。研究结果表明,这种石英毛细管内弧光放电等离子体的气体温度约为(1 100±50)K;电子密度数量级在1014 cm-3;电子温度约为(14 515±500)K。     

傅里叶变换法计算焊接电弧光谱Stark展宽研究

利用电弧光谱,采用Stark展宽法计算电子密度是测量等离子体电子密度最有效、最准确的方法。而如何从众多展宽机制复合的谱线中分离出Stark展宽是应用Stark展宽法的难点。利用傅里叶变换从测得的光谱线形中分离出Lorentz线形,从而准确获得Stark展宽,并且计算了TIG焊电弧等离子体电子密度的分布。这种方法不需要准确测量电弧温度,不需要测量仪器展宽并且对数据有去噪作用。计算结果表明：在轴线上,TIG焊电弧电子密度随着离钨极距离的增大而减小,变化范围在1.21×1017~1.58×1017 cm-3之间;在径向,电子密度随离轴距离的增大而降低,在靠近钨极区域具有离轴最大的性质。     

Stark线形与ICF等离子体诊断

本文理论计算了ICF等离子体中离子或原子的发射谱线线形函数,该线形主要是由Stark效应产生的.我们的研究表明该谱线线形函数的宽度随电子温度变化很缓慢,而随电子密度变化很敏感.结合局部热动平衡理论,并利用实验测量的氩(Ar)和硫(S)的α线与β线的线强比,分别估算出等离子体的电子温度为885 eV和793 eV.通过理论计算的Stark线形函数与ICF实验谱线的比较,估算出ICF等离子体的电子密度Ne=1.0×1024.     

Ar/CH4等离子体射流发射光谱诊断研究

为了更加深入的研究大气压条件下Ar/CH₄等离子体射流的放电机理和其内部电子的状态,通过自主设计的针-环式介质阻挡放电结构,在放电频率10 kHz、一个大气压条件下产生了稳定的Ar/CH₄等离子体射流,并利用发射光谱法对其进行了诊断研究。对大气条件下Ar/CH₄等离子体射流的放电现象及内部活性粒子种类进行诊断分析,重点研究了不同氩气甲烷体积流量比、不同峰值电压对大气压Ar/CH₄等离子体射流电子激发温度、电子密度以及CH基团活性粒子浓度的影响规律。结果表明,大气压条件下Ar/CH₄等离子体射流呈淡蓝色,在射流边缘可观察到丝状毛刺并伴有刺耳的电离声同时发现射流尖端的形态波动较大;通过发射光谱可以发现Ar/CH₄等离子体射流中的主要活性粒子为CH基团,C,CⅡ,CⅢ,CⅣ,ArⅠ和ArⅡ,其中含碳粒子的谱线主要集中在400~600 nm之间,ArⅠ和ArⅡ的谱线分布在680~800 nm之间;可以发现CH基团的浓度随峰值电压的增大而增大,但CH基团浓度随Ar/CH₄体积流量比的增大而减小,同时Ar/CH₄等离子体射流中C原子的浓度随之增加,这表明氩气甲烷体积流量比的增大加速了Ar/CH₄等离子体射流中C-H的断裂,因此可以发现增大峰值电压与氩气甲烷体积流量比均可明显的加快甲烷分子的脱氢效率,但增大氩气甲烷体积流量比的脱氢效果更加明显。通过多谱线斜率法选取4条ArⅠ谱线计算了不同工况下的电子激发温度,求得大气压Ar/CH₄等离子体射流的电子激发温度在6 000~12 000 K之间,且随峰值电压与氩气甲烷体积流量比的增大均呈现上升的趋势;依据Stark展宽机理对Ar/CH₄等离子体射流的电子密度进行了计算,电子密度的数量级可达1017 cm-3,且增大峰值电压与氩气甲烷体积流量比均可有效的提高射流中的电子密度。这些参数的探索对大气压等离子体射流的研讨具有重大意义。     

大气压微等离子体射流电子密度研究

采用微空心阴极放电装置,利用光学方法和电学方法研究了大气压流动Ar和N₂混合气体中产生的微等离子体射流特性。研究发现,随着电源输入功率增大到一定数值,微空心阴极装置中两个电极间气体发生击穿,通过击穿气隙气体的流动会沿着气流方向产生最大为4 mm的等离子体射流。放电电流为准连续的脉冲放电形式,其中放电电流脉冲宽度约为0.1 μs。分别利用爱因斯坦方程和等离子体发射光谱中谱线的Stark展宽方法计算了电子密度。结果发现,2种计算方法得出的微等离子体射流的电子密度均在1015·cm-3的量级。研究还发现,功率对微等离子体射流电子密度影响不大。利用气体击穿理论,对以上结论进行了定性分析。     

小尺寸瞬态等离子体电子密度光谱法试验研究

本文对SCB等离子体发射光谱进行了试验研究,在局部热力学平衡条件下,用AlⅠ394.40nm谱线Stark的展宽法测量了SCB等离子体的电子密度;在发射光谱和Saha方程理论的基础上,设计并建立一套测试仪器,时间分辨率为0.1μs,将其测量的电子密度与同种试验条件下的Stark展宽法得到的结果相比较,电子密度的数量级都为1015cm-3－1016cm-3,且随时间的变化的规律相同。     

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采用光学多通道分析仪等设备对532nm YAG激光诱导产生的Al等离子体光谱进行了时空分辨测量,得到了等离子体时空分辨光谱。利用局部热平衡(LTE)模型和谱线的Stark展宽计算得到了等离子体电子温度和电子密度的时空演化曲线,获得了与文献[9～11]一致的结果。     

激光诱导等离子体中Al原子发射光谱的时间、空间演化特性实验研究

实验测定了激光诱导Al等离子体中390.068,394.4,396.152,466.3056 nm等谱线的时间、空间分辨特性,由发射光谱线的强度和Stark展宽计算了 Al等离子体中的电子密度,并由实验结果讨论了电子密度的时间空间演化特性.实验结果表明,当延时在100～1500 ns变化时,等离子体巾的电子密度变化范围为0.02×1017～1.4×1017cm-3,在沿激光束方向上,当距离靶表面0～1.8 mm范围内变化时,相应的电子密度范围为0.28x1017～0.95×1017cm-3,等离子体电子密度在沿激光束方向上具有很好的对称性.     

Determination of the Electron Density in an Argon Laser Plasma by Spectroscopy of the Hydrogen Hα and Hβ Lines

From measurements of the H_α and H_β spectral line profiles in a plasma, a method is developed which allows to separate the contributions of Doppler and Stark broadening. This method is superior to the deconvolution of Voigt profiles, in particular, when the lines are of low intensity. The electron density in the plasma can be calculated from the Stark broadening. An example is the low pressure (p ≈ 1 hPa) arc discharge of argon ion lasers which is characteristised by electron densities of approximately 10¹⁴ cm^?3 at heavy particle temperatures of about 10⁴ K. These plasma parameters lead to a broadening of the Balmer H_α and H_β spectral lines of hydrogen, which has a low concentration within the discharge area. The spectral lines are broadened due to the electron density dependent Stark effect and the temperature responsive Doppler effect. The results are consistent with predictions of the argon ion laser modelling.     

Kinetic temperature and electron density measurement in?an?inductively coupled plasma torch using degenerate four-wave mixing

Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively coupled plasma. Measurements are performed in a 1 kW, 27 MHz radio-frequency plasma using a continuous-wave, tunable 811.5 nm diode laser to excite the 4s³P₂→4p³D₃ argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000±150 K. Electron densities measured range from 6.1 (±0.3)×10¹⁵ cm⁻³ to 10.1 (±0.3)×10¹⁵ cm⁻³. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. The Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.     

Measurements of electron density and Stark width of neutral helium lines in a helium arc plasma

Electron densities in an atmospheric helium arc plasma have been measured with the Stark broadening parameters of helium spectral lines. The spatially distributed radiation intensities are converted to plasma emission coefficients at every wavelength by means of Abel inversion. From the inverted profiles of He I lines of 4713 ?, 5016 ?, and 6678 ? electron density has been calculated, which ranges from 0.5 ×10¹⁶ to 4 ×10¹⁶ cm^-3 for a helium arc with current 200 A. Stark widths of He I lines of 3889 ? and 7065 ? are determined based on the measurements and compared with existing data.     

Axial variation of electron number density in thermal plasma spray jets

The electron number density has been measured in a plasma spray torch using Stark broadening of H and Ar-I (430 nm) line. A small amount of hydrogen (1% by volume in argon gas) was introduced to study the H line profile. Axial variation of electron number density has been determined up to a distance of 20 mm from the nozzle exit point of spray torch. The plasma torch was operated at 5 and 10 kW power level and flow of argon was kept at 25 liters per minute. Using the measured excitation temperature data under same experimental conditions, the electron number density has also been calculated using Saha equation. Comparison of electron number densities measured from Stark broadening with those derived from excitation temperature measurements under the assumption of local thermodynamic equilibrium (LTE) in thermal plasma jets indicate about the deviation from LTE in thermal plasma jets. The electron number density measurement using Stark broadening of Ar-I (430 nm) line will be particularly useful when only argon gas is used in thermal plasma jets.Received: 6 January 2003, Published online: 22 July 2003PACS: 52.70.Kz Optical (ultraviolet, visible, infrared) measurements - 52.77.-j Plasma applications - 52.25.-b Plasma properties     

Measurement of the Stark broadening parameters of some singly ionized argon lines

Half-widths of fifteen Stark broadened argon II lines have been measured in argon plasma behind the reflected shock wave produced in an electromagnetically driven “T” tube. The plasma electron density was determined by the laser interferometry at three different wavelengths, while the plasma temperature was measured from relative intensities of A II lines. Temperatures were in the range 8,500–16,500 °K; electron densities varied from 1.82 to 3.94 · 10¹⁷ cm^?3. The measured A II linewidths are compared with theoretical and other experimental results. It is shown that a) the broadening of A II lines is in good agreement with the theory, b) line broadening increases linearly with electron density, and c) the Stark broadened lines follow the dispersion profile to the distance of at least three halfwidths from the line center.     

Experimental Stark broadening studies of the CI transition 3s1P1o ? 3p1S0 at 833.5 nm

Experimental Stark broadening studies of the infrared CI transition 3s ¹ P ₁ ^o − 3p ¹ S ₀ at 833.5 nm are reported for the first time. A high-current wall-stabilized arc, operated in a mixture of helium, argon, carbon dioxide and hydrogen, was applied as the plasma source. Radiation emitted from homogeneous and optically thin plasma layers was analyzed. Stark broadening studies of the selected CI transition and the hydrogen Balmer β line were performed. As expected from theoretical considerations, the CI line width depends linearly on the electron density of the plasma. Applying theoretical Stark broadening data for the H _gb line, the measured Stark widths of the CI line were calibrated for the purpose of electron density determination in low temperature plasmas.     

On plasma parameters of a self-organized plasma jet at atmospheric pressure

Electron temperature and electron concentration in the active zone of a miniaturized radio frequency (RF) non-thermal atmospheric pressure plasma jet in argon have been determined using two independent approaches: the spectroscopic measurement of the broadening of Balmer H_b_\beta and H_g_\gamma lines and a time-dependent, spatially two-dimensional fluid model of a single discharge filament. The plasma source has been configured as a capacitively coupled RF jet (27.12 MHz, 8 W generator output power) with two outer ring electrodes around a quartz capillary with diameter of 4.0 mm between which Ar flows at typical rates of 0.3 slm. The discharge has been operated in a self-organized mode, where equidistant, stationary filaments rotate regularly with a constant frequency at the inner wall of the outer capillary. For the purpose of calculating the spectral line broadening different models applicable at higher electron concentration have been evaluated. Resulting electron concentrations are between 2.2 and 3.3 × 1014 cm^-3. The calculation according to the line broadening model provides electron temperatures between 20 000 and 30 000 K which is in agreement with the results of the fluid model calculations. Here, a broad radial profile with a maximal value of about 22 000 K in the centre of the column and an electron concentration of about 7 × 10¹³ cm^-3 have been obtained. Moreover, the results of the model calculations reveal a structural change of the filament from the dielectric surface through the sheath to the column. The axially inhomogeneous region has an extension of about 0.5 mm. In the column a concentration of about 10¹³ cm^-3 has been found for the excited argon atoms, whose collisions with electrons represent the most important ionization channel there.     

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。     

High density measurements of the Stark broadened profile of the He(II)4686 Å line

The Stark broadened profile of the He(II)4686 Å line has been scanned in the electron density range of 1–3 × 10¹⁸ cm^-3. The electron temperature, as determined from the line to continuum ratio, ranged from 9.4 to 19.9 eV. The plasma which emitted the He(II)4686 Å line was created in a 60-kJ theta pinch operated with a high fill pressure (3 and 5 torr) of pure helium. Electron densities were calculated from the half-half widths of the He(II)4686 Å line using two Stark broadening theories. These electron densities are compared with the electron densities determined from the absolute value of the continuum intensity and a total sweep up compressional model. The two theoretical models predict electron densities in good agreement with the electron densities from the absolute value of the continuum intensity.     

Experimental stark parameters of carbon C II 2993 Å line

Total Stark profiles of the C II 2993 Å line of a plasma jet of a slit discharge with an evaporating wall. In the interval of electron densities of 10¹⁷ to 6 × 10¹⁷ cm^?3, the electron impact width, the ionic broadening and the shift of the intensity maximum of the line are measured. It is found that, at an inversely quadratic dependence of the electron impact width on the electron concentration, the Stark shift and the ionic contribution to the total width of the profile are linear. It is noted that calculated values of the shift regularly exceed measured values, while the signs of the measured and calculated shifts coincide. The method of approximating experimental data is proposed, which takes into account the interrelation of the main Stark parameters in plasma with a strong interparticle interactions.