Transport properties of high temperature air in local thermodynamic equilibrium

In the paper new calculated transport coefficients of air in the temperature range 50-100 000 K are presented. The results have been obtained by means of the perturbative Chapman-Enskog method, assuming that the plasma is in local thermodynamic equilibrium (LTE). The calculations include viscosity, thermal conductivity, electric conductivity and multicomponent diffusion coefficients. For the calculation, a recent compilation of collision integrals obtained by Capitelli et al. [1] has been utilized. Analytical expression for all transport coefficients and thermodynamic parameters of the air plasma are also reported. Received 17 November 1999     

双温度氩-氮等离子体热力学和输运性质计算

获得覆盖较宽温度和压力范围内的等离子体热力学和输运性质是开展等离子体传热和流动过程数值模拟的必要条件.本文通过联立Saha方程、道尔顿分压定律以及电荷准中性条件求解等离子体组分;采用理想气体动力学理论计算等离子体热力学性质;基于Chapman-Enskog方法求解等离子体输运性质.利用上述方法计算了压力为0.1, 1.0和10.0 atm (1 atm=101325 Pa),电子温度在300—30000 K范围内,非局域热力学平衡(电子温度不等于重粒子温度)条件下氩-氮等离子体的热力学和输运性质.结果表明压力和非平衡度会影响等离子体中各化学反应过程,从而对氩-氮等离子体的热力学及输运性质有较大的影响.在局域热力学平衡条件下,计算获得的氩-氮等离子体输运性质和文献报道的数据符合良好.     

Spectroscopic studies of laser-produced plasmas formed in CO and CO2 using 193, 266, 355, 532 and 1064 nm laser radiation

The wavelength dependence of laser-produced breakdown in air, CO and CO₂ has been studied using the four Nd:YAG harmonics (266 nm, 355 nm, 532 nm and 1064 nm) and the ArF-excimer laser (193 nm). Breakdown thresholds at these wavelengths are reported for air, CO and CO₂. A significant reduction in the breakdown thresholds for both CO and CO₂ is apparent when comparing 193 nm with the four Nd:YAG harmonics. This reduction is attributed to the resonance-enhanced two-photon ionization of metastable carbon atoms generated in the laser focus at the ArF-laser wavelength. In addition to reporting breakdown thresholds, the laser-produced plasmas in CO and CO₂ are characterized in terms of plasma temperatures and electron densities which are measured by time-resolved emission spectroscopy. Electron densities range from 9 × 10¹⁷ cm^–3 to 1 × 10₁₇ cm^–3. Excitation temperatures range from 22 000 K at 0.2 µs to 11 000 K at 2 µs. Ionization temperatures range from 22 000 K at 0.1 µs to 16 000 K at 2 µs. Evidence is presented to indicate that, like ArF-laser-produced plasmas, Nd:YAG-laser-produced plasmas formed in CO and CO₂ are in or near a state of Local Thermodynamic Equilibrium (LTE) soon after their formation.     

Investigations on the mechanism of carrier transport in plasma polymerized pyrrole thin films

Plasma polymerization is found to be an excellent technique for the preparation of good quality, pinhole-free, polymer thin films from different monomer precursors. The present work describes the preparation and characterization of polypyrrole (PPy) thin films by ac plasma polymerization technique in their pristine and in situ iodine doped forms. The electrical conductivity studies of the aluminium-polymer-aluminium (Al-polymer-Al) structures have been carried out and a space charge limited conduction (SCLC) mechanism is identified as the most probable mechanism of carrier transport in these polymer films. The electrical conductivity shows an enhanced value in the iodine doped sample. The reduction of optical band gap by iodine doping is correlated with the observed conductivity results.     

惰性气体磁流体发电机的等离子体性能分析

惰性气体磁流体发电机将热能直接转换为电能,本身无转动部件,具有转换效率高、功率密度大等特点,在大功率电源方面具有重要发展前景。等离子体性能是影响惰性气体磁流体发电机输出的关键因素之一,文章介绍了3种典型的电导率计算模型（Spitzer模型、Z&L模型、M&G模型）;描述了惰性气体添加种子的等离子体组分,并建立了适合于惰性气体的电导率计算模型;研究了温度、压力等参数对等离子体性能的影响.      

Dependence of Arc Plasma Dispersion Capability on its Temperature

The relationship between the dispersion capability and the temperature of argon arc plasma at 1 atm is deduced in view of the plasma＇s refractive index equation. The results indicate that argon arc plasma has a normal dispersion and its dispersion capability is nonlinear to the plasma＇s temperature in a wide range of temperature and wavelength region. According to the results of numerical calculation, the preferred optical methods are believed to be suitable for the diagnosis of argon arc plasma in different temperature regions.     

The effect of annealing on the proton conductivity of Mg-doped α-Al2O3

In order to evaluate the effect of annealing treatment on the proton conductivity of ??-alumina, the electrical conductivity of Mg-doped polycrystalline ??-alumina kept at 1,873?K under various conditions of the surrounding atmosphere and then cooled in the furnace was measured in the temperature range 1,173?C1,473?K. The H⁺/D⁺ isotope effect on the electrical conductivity was also examined under a hydrogen atmosphere at 1,273?K. The protonic conductivity measured at 1,273?K increased with the increase in the activity of oxygen and water vapor in the annealing atmosphere at 1,873?K. It is considered that the solubility limit of magnesium ions in ??-alumina in equilibrium with the small amount of the spinel phase increased with the increase in the activity of oxygen and water vapor at 1,873?K. This enhanced amount of magnesium ions is frozen in a non-equilibrium state to 1,273?K and works as the enriched acceptor dopant for the incorporation of protons.     

Xenon plasma with caesium as additive

The concentration dependence of xenon plasma with caesium as additive in the temperature region of 2 000 K to 20 000 K has been analysed. Plasma has been considered as weakly nonideal in the complete local thermodynamic equilibrium and the interaction between plasma and vessel walls was not taken into account. The values of some of the parameters for nonideality of plasma with 1% of caesium (=0·01010) and 10% of caesium (=0·11111) are computed, for initial pressure in plasma ofp ₀=13 000 Pa and initial temperatureT ₀=1 000 K. Also the ratio of electrical conductivity of plasma computed by Lorentz's formula and electrical conductivity computed by Spitzer's formula in the same temperature interval has been analysed.     

Measurement of neutral gas temperature in inductively coupled plasmas

Dependence of the neutral gas temperature on the gas pressure and discharge power in an inductively coupled plasma source has been investigated using optical emission spectroscopy. Both nitrogen and argon plasmas have been studied separately. In the case of argon plasma, about 5% nitrogen was added to the total gas flow as an actinometer. The maximum temperature was found to be as high as 1850 K at 1 Torr working pressure and 600 W radiofrequency power. The temperature increases almost linearly with the logarithm of the gas pressure, but changes only slightly with the discharge power in the range of 100–600 W. In a nitrogen plasma, a sudden increase in the neutral gas temperature occurs when the gas pressure is increased at a given discharge power. This suggests a discharge-mode transition from the H-mode (high plasma density) to the E-mode (low plasma density). In the H-mode, the gas temperature is proportional to the logarithm of the gas pressure, as in the argon plasma. However, the gas temperature increases almost linearly with the discharge power, which is in contrast to the case of argon plasma. The electron density in the nitrogen plasma is about 10% of that in the argon plasma. This may explain the observation that the nitrogen neutral temperature is always lower than the argon neutral temperature under the same discharge power and gas pressure.     

闪电首次回击过程中通道温度与电导率的演化特征

利用以高速摄像机为记录系统组装的无狭缝摄谱仪,在青海地区获得了多次云对地闪电首次回击过程400-900 nm波长范围的时间分辨光谱,分别计算了闪电电流核心通道和外围发光通道的温度;结合空气等离子体的传输理论,获得了闪电通道的电导率,探讨了回击过程中通道温度及电导率的演化特征.结果表明,闪电电流核心通道的温度比外围通道高约5000-7000 K,并且,与以往关于通道峰值温度持续时间的观点不同,回击过程中,通道保持高温的时间远远大于峰值放电电流存在的时间,在回击电流缓慢减小的数百微秒内,核心电流通道维持20000 K以上高温,这一特性是热效应导致雷电灾害的主要根源.     

闪电首次回击过程中通道温度与电导率的演化特征

利用以高速摄像机为记录系统组装的无狭缝摄谱仪,在青海地区获得了多次云对地闪电首次回击过程400-900 nm波长范围的时间分辨光谱,分别计算了闪电电流核心通道和外围发光通道的温度;结合空气等离子体的传输理论,获得了闪电通道的电导率,探讨了回击过程中通道温度及电导率的演化特征.结果表明,闪电电流核心通道的温度比外围通道高约5000-7000K,并且,与以往关于通道峰值温度持续时间的观点不同,回击过程中,通道保持高温的时间远远大于峰值放电电流存在的时间,在回击电流缓慢减小的数百微秒内,核心电流通道维持20000K以上高温,这一特性是热效应导致雷电灾害的主要根源.     

Enskog-Landau kinetic equation for multicomponent mixture. Analytical calculation of transport coefficients

The Enskog-Landau kinetic equation is considered to describe non-equilibrium processes of a mixture of charged hard spheres. This equation has been obtained in our previous papers by means of the non-equilibrium statistical operator method. The normal solution of this kinetic equation found in the first approximation using the standard Chapman-Enskog method is given. On the basis of the found solution the flows and transport coefficients have been calculated. All transport coefficients for multicomponent mixture of spherical Coulomb particles are presented analytically for the first time. Numerical calculations of thermal conductivity and thermal diffusion coefficient are performed for some specific mixtures of noble gases of high density. We compare the calculations with those ones for point-like neutral and charged particles. Received 10 June 1999 and Received in final form 15 October 1999     

Electrostatic fluctuations in nonequilibrium plasmas with particle collisions

We present a method for calculation of plasma fluctuations in a nonequilibrium plasma with stable particle distribution functions. The method takes into account particle collisions and collective particle interactions which affect the collision process. In contrast to the known approaches, our method makes no reference to a specific form of the collision integrals and distribution functions. Using the developed method, we calculate the high-frequency spectrum of the electric field fluctuations in a collisional plasma with arbitrary particle distribution functions.     

General electrical transport properties of polycrystalline multi-layered metallic thin films

We have derived, following the recent theoretical calculation of the electrical conductivity of multi-layered metallic thin films, a general solution of the electrical conductivity for those films with grain structures, since those structures give important contributions to the electrical transport properties of polycrystalline thin film. The temperature coefficients of resistivity have also been obtained.     

Evolution of statistical properties of ion temperature gradient driven turbulence during the formation of internal transport barrier in a tokamak

Statistical properties of ion temperature gradient driven turbulence and anomalous flux are analysed in plasmas with low and improved energy confinement. The turbulence is simulated using the three dimensional fluid code, where the source is prescribed and the turbulence and temperature profile evolve self-consistently. The transition to the improved core confinement with an internal transport barrier is obtained by increasing the heating power. It is found that the momentums of the probability distribution function of flux fluctuations reduce to their Gaussian values when the transport barrier on the temperature profile forms. The formation of the oscillating structure with the properties of linear wave has been found at very high heating power. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreux, Switzerland, June 23–24, 2002.     

One-component-plasma: Going beyond Debye-Hückel

Using field-theoretic methods, we calculate the internal energy for the One-Component Plasma (OCP). We go beyond the recent calculation by Brilliantov [N. Brilliantov, Contrib. Plasma Phys. 38, 489 (1998)] by including non-Gaussian terms. We show that, for the whole range of the plasma parameter , the effect of the higher-order terms is small and that the final result is not improved relative to the Gaussian theory when compared to simulations. Received 12 April 1999     

An adaptive line-by-line—statistical model for fast and accurate spectral simulations in low-pressure plasmas

An adaptive grid method is proposed for the simulation of low-pressure plasma radiation. The method relies on two complementary approaches which significantly reduce calculation times and the size of the obtained grids: Weak lines are calculated as a so-called “pseudo-continuum”, hence reducing the number of calculated lines, and a numerical algorithm has been developed for accurately calculating Voigt lineshapes using a minimum number of points. The method is fully user-parametric, allowing the choice of privileging calculation efficiency, or alternatively privileging the accuracy of the computed spectra. Sample radiative transfer calculations are presented, which show the efficiency of the method, also providing some guidelines on how to define lineshape calculation parameters, depending on the problem to be solved.     

双温度氦等离子体输运性质计算

获得覆盖较宽温度和压力范围内的等离子体输运性质是进行等离子体传热和流动过程数值模拟的必要条件.本文采用Saha方程计算等离子体组分, 采用基于将Chapman-Enskog方法扩展到高阶近似的方法, 计算获得了电子温度(T_e)不等于重粒子温度(T_h)的情形下, 在300 K到40000 K的温度范围内氦等离子体的黏性、热导率和电导率. 研究结果表明压力和热力学非平衡参数(θ =T_e/T_h)对氦等离子体的输运性质有较大的影响. 在局域热力学平衡条件下,计算获得的氦等离子体输运性质和文献报道的数据符合良好.     

Theoretical computation of the electrical conductivity of thermalplasmas-application to plasma torch design of an electrothermal launcher

Designing a plasma torch that allows the ignition of gun propellant is generally complex. In this paper, however, we show that it is possible to design a torch from using simplified calculation of electrical conductivity with the help of an experienced design method (Doehlert matrix). First, we explain how to obtain plasma composition both at and out of thermal equilibrium. Then, we compare the simplified calculation with the complete calculation of electrical conductivity. Then, we construct a Doehlert matrix as a function of temperature and thermal nonequilibrium. Finally, we study the length/diameter ratio versus the length and resistivity     

局域热力学平衡态空气电弧等离子体输运参数计算研究

空气电弧等离子体的物性参数为空气电弧放电过程的仿真提供了可靠的微观理论基础和参数输入. 假定体系处于局域热力学平衡态, 基于Chapman-Enskog理论, 采用Sonine多项式三级展开(对黏滞系数采用二级展开) 得到的输运参数表达式, 数值计算得到了不同气压条件下(0.1 atm-20 atm, 1 atm = 1.01325×10⁵ Pa)、 不同温度范围内(300-30000 K) 空气电弧等离子体的输运参数(扩散系数、黏滞系数、热导率、电导率). 与以往的理论研究相比, 最新的相互作用势和碰撞截面研究成果被应用到涉及粒子的碰撞积分计算中, 提高了输运参数计算结果的精度和可靠性.