Path Integral Formalism for Line Broadening in Plasmas: Lyman‐α case

Using the path integral formalism, the fine structure and dynamics effects are taken into account for the study of the spectral line broadening in plasmas. A compact expression of the dipolar autocorrelation function (DAF) for an emitter in the plasma is derived for Lyman alpha lines with fine structure. The expression of the DAF takes into account the dynamics effects, which are represented by the time autocorrelation function of the electric microfield. The spectral line for the Lyman‐alpha case has been obtained in a compact form and plotted in the quasi‐static approximation and compared to a line obtained by a simulation. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

不同微场分布函数下的光谱线型

根据光谱学,总的光谱线型是各种加宽机制的卷积结果。考虑到等离子体中的离子碰撞,Stark加宽本质上是一种非对称的光谱线型, 其中微场分布函数对光谱线型起着非常关键的作用。该文利用不同的微场分布函数研究了微场分布函数对总的光谱线型的影响。研究结果表明,在电子加宽参数和离子加宽参数很小时,不同微场分布函数对整个光谱线型的影响基本相似,但随着离子加宽参数的增加,3种不同的微场分布函数对Stark光谱线型的影响逐渐增加; 随着电子加宽参数的增加,不同的微场分布函数对Stark光谱线型的影响也逐渐增加; 但总体上Holtsmark分布和Nearest-Neighbor场分布下的光谱线型差别较小,但是Mayer模型对光谱线型影响较大。特别是,当离子加宽参数较大时,Mayer模型对光谱线型的影响异常明显,这也正说明离子间碰撞剧烈时对光谱线型的影响很大。该结果对等离子体参数诊断有一定参考价值。     

Effects of individual line shapes on composite profiles and line series

We consider (i) the use of approximate ion microfield distributions as inputs into spectral line shapes and (ii) the effects of individual lines on unresolved transition array (UTA) profiles observed in highly ionized plasmas. Spectral line shapes and line wings have significant effects on mean opacity calculations.     

Effect of a magnetic field on the radiation emitted by a nonequilibrium hydrogen and deuterium plasma

Radiative transfer in a nonequilibrium plasma in an external electric field is considered. The system of kinetic equations determining the populations of atomic levels is written taking into account the combination of collision and radiative processes and is solved together with the kinetic equation for photon of various frequencies, which are emitted and absorbed in the radiative transitions from the states of the continuous and discrete spectra. The shape of spectral lines is determined from the solution of the quantum-mechanical problem on the emission of an atom in the electric field of the plasma and an external magnetic field, taking the Doppler effect into consideration. The developed approach is used in the model calculation of radiative transfer under the conditions corresponding to the edge plasma in a tokamak, which is simulated by a homogeneous plane layer of a deuterium plasma. It is shown that the joint action of the external magnetic field and the electric plasma fields considerably affects the spectral and integrated characteristics of the radiation.     

Determination of temperature profiles from optically thick lines

A method for the evaluation of high-pressure discharge temperature profiles is proposed, which is based on a numerical solution of the radiative transfer equation. The measured quantities that have to be provided for the numerical evaluation are readily obtainable because only the absolute side-on intensity of a spectral line as a function of the lateral coordinate has to be measured. The method has been applied to several optically thick mercury lines. A comparison with temperatures obtained from optically thin lines shows good agreement. This method has the following two advantages: (i) temperature determination is possible in cases where no optically thin line is available, (ii) using optically thick lines of transitions with low excited states (e.g., resonance lines), the temperature profile can be determined for larger radii than from optically thin lines.     

Analysis of an Inhomogeneous Semitransparent Plasma by the Lines in the Emission Spectrum

Using the methods of numerical simulation, we have investigated the dependence of the intensity and parameters of the spectral line profiles in the radiation of semitransparent plasma on its optical thickness, the degree of inhomogeneity, and the parameter distribution. As a model, we used the equilibrium plasma of argon with a given temperature profile on the observation line. The calculation has been performed for the spectral lines of the argon atom characterized by different broadening constants. On the basis of the results obtained it has been shown that it is possible to diagnose the plasma and determine the degree of its inhomogeneity and reabsorption by the parameters of the self-reversed profiles of the spectral lines. To diagnose the plasma in the absence of self-reversal, we propose to use the line intensities in the emission spectra of the plasma, including those obtained by probing it by its self-radiation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 404–411, May–June, 2005.     

Theoretical basis for the quantitative characterization of impurities in n-type III–V compound semiconductors by photoelectromagnetic spectroscopy

Theoretical results are described for the quantitative characterization of impurities by photoelectromagnetic spectroscopy. The diagnostics is based on a study of profiles of spectral lines. Line broadening is caused mainly by the influence of electric fields of charged impurities on neutral donors, in which optical transitions occur. The profile of the spectral line for the intradonor transition between 1s and 2p₀ states is calculated taking into account Coulomb correlations in the distribution of charged impurities in space at low temperatures. Calculations were carried out by computer simulation of the impurity system over a wide range of compensation degrees. This parameter can be found by a study of line profile evolution with an increase of temperature. The concentration of donors can then be found by a comparison of the experimental curve with the theoretical line profile for the corresponding degree of compensation. For low compensations an analytical theory is developed for the evolution of line profile with temperature.     

Contribution to Calculation of Ion Microfield Nonuniformity Effect on the Asymmetry of Lyman‐α Line in Dense Plasma

The high orders of Stark effects on spectral line shapes are examined in the ion‐static and electron‐impact ap‐proximations. At first the distribution functions of the spatial derivative of the ion microfield in He⁺ plasma are calculated for different plasma conditions when the coupling parameter is weak. We present new results about the spatial derivative ion microfield distributions and apply them to show the asymmetry of the Lyman‐α (Ly‐α) line in He⁺ plasma. At the second stage we show that asymmetry is affected by the spatial derivative tensor of the local ion electric field. We have used the Monte‐Carlo simulation (MCS) to compute the distribution functions for all tensor components and use them to solve the evolution equation of emitter whose solution serves to compute and therefore to show the line shape asymmetry. Good agreement of our distribution functions of ion microfield gradients and the line asymmetry with other results are obtained (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electric Microfield Distributions in Dense One‐ and Two‐Component Plasmas

The electric microfield distributions have been calculated using an integral‐equation method for one‐component plasmas proposed by Iglesias [1] and the coupling‐parameter integration technique for two‐component plasmas proposed by Ortner et al. [2]. Electric microfield distributions are studied in the frame of the Kelbg pseudopotential model, taking into account quantum‐mechanical effects (diffraction, quantum symmetry effects) and screening effects. The screened pseudopotential is represented in a numerically approximated form. The results are compared with simulation results obtained by other authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

强迫耗散系统的有序结构和系统的发展(Ⅰ)，最小熵产生原理和有序结构

一个系统的发展总是由不可逆热力过程和非线性动力过程所驱动.将大气动力学方程组同考虑了动能变化的Gibbs关系结合起来构建的熵平衡方程，才能更好地描述大气系统的不可逆热力过程和非线性动力过程.至今非平衡态热力学仅利用Onsager线性唯象关系证明了最小熵产生原理.利用新建立的熵平衡方程和大气动力学方程的性质证明，最小熵产生原理在热力学线性区和非线性区都是普遍成立的.且当热量输送平衡、水汽输送平衡和动量输送平衡时，系统达到不可逆过程最弱的最小熵产生热力学状态.当系统又是动力平衡且无平流时，这种最小熵产生态就是 关键词： 非线性热力学 熵产生 最小熵产生原理 有序结构     

Diagnostics of Langmuir oscillations in a superdense plasma

The level and the angular distribution of Langmuir oscillations in a dense plasma produced on the Phoenix plasma radiation source (PRS) were measured. Line profiles of several lines in the Lyman series of Al XIII were measured using crystal spectrometers. A spectral line shape model was used, which attempted to take into account all significant broadening mechanisms. The parameters of the plasma and the Langmuir oscillations were found by generating profiles using the model and comparing these profiles to the experimental spectra. The strength of the Langmuir oscillations was found to be E₀≈1-9 GV/cm, indicative of a strong Langmuir turbulence. The polarization analysis of the profiles of the Al XIII Lyman γ line has shown that the Langmuir oscillations develop anisotropically, primarily in the direction of the plasma current     

Effect of parallel flows and toroidicity on cross-field transport of pellet ablation matter in tokamak plasmas

The first complete set of time-dependent equations describing the cross-field drift of ionized pellet ablation matter in tokamak plasma caused by polarization in the nonuniform magnetic field has been developed and solved numerically. Important new features impacting the drift dynamics have been identified, including the effect of pressure profile variations in the tokamak plasma, curvature drive by near-sonic field-aligned (parallel) flows, and the rotational transform of the magnetic field lines, and are considered from the viewpoint of the parallel vorticity equation. These new features are necessary to obtain favorable quantitative agreement between theory and experimental fuel deposition profiles for both inner and outer wall launched pellet injection cases on the DIII-D tokamak.     

Calculation of radiative heat transfer in argon arc plasmas

Radiation emission and absorption in arc plasmas are important energy transfer processes. Exact calculations, though possible in principle, are usually impossible in practice because of the need to treat a large number of spectral lines and also the continuum radiation in the whole spectrum range. Recently, we have used an approximate method of partial characteristics to evaluate the radiation intensities, radiation fluxes and the divergence of radiation fluxes for SF₆ arc plasma with cylindrical symmetry. In this paper, we have extended our calculations toargon arc plasmas for the plasma pressures of 0.1, 0.5 and 1.0 MPa. We have calculated the coefficients of absorption for Ar plasmas at temperatures from 300 to 35 000 K, and have used these coefficients to calculate the partial characteristics. Both the continuum and the line spectra have been included in calculations. We have taken into account the radiative photo-recombination and bremsstrahlung for the continuous spectrum, and over 500 spectral lines for the discrete spectra.The method of partial characteristics has been applied to three-dimensional calculations of radiative heat transfer — i.e. radiation intensity, radiation flux and its divergence — in simplified temperature profiles. Conclusions have been made concerning validity and utilization of the method of partial characteristics in general gas dynamics problems.     

A new approach to determination of the asymmetry parameter of Stark-broadened isolated spectral lines

A new approach to evaluation of asymmetry parameters of Stark-broadened isolated spectral lines is presented. The procedure is discussed on the example of the N I line at λ = 9822.75 Å. Line shape measurements were performed using a wall-stabilized arc, operated at atmospheric pressure. The radiation of the plasma, emitted from homogeneous plasma layers in end-on direction, was measured using a grating spectrometer equipped with a two-dimensional CCD detector. Griem-like profiles, convoluted with the corresponding Doppler and apparatus profiles, were fitted to experimental data. In this way the Stark broadening parameters (electron impact widths, shifts and asymmetry) have been determined. Detailed analysis of the line shapes shows that the standard Griem-like profile does not explain the observed line asymmetry satisfactorily. The results of preliminary studies indicate that including collision-duration effects in profile calculations provides a better agreement between experiment and calculations. PACS. 32.70.Jz Line shapes, width, and shift – 52.70.Kz Optical (ultraviolet, visible, infrared) measurements.     

Das Mikrofeld im Plasma

By taking full account of the Coulomb interaction and energy conservation, the probability distribution of the electric and magnetic microfield in an ionized gas is calculated. It results a Gaussian distribution instead of the hitherto used Holtsmark function and its variants which exhibit certain deficiencies. The mean square electric field is found to be proportional to the temperature, in analogy to the Nyquist formula. The probability of finding an atomic charge in the vicinity of another is established. With this, the time correlation function of the microfield and an average of the correlation time is deduced. Applications to the theory of transport phenomena and spectral line broadening are briefly discussed.     

Plasma temperature measurements using self-absorbed spectral lines: A discussion of the methods due to Bartels and Kruithof

The plasma temperature measuring methods due to Bartels and Kruithof, which make use of self- absorbed spectral lines, are particular solutions of the radiative transfer equation. For conditions found in typical high-pressure gas discharges used as light sources, the radiative transfer equation has been solved numerically. These results are used to investigate the influence of several of the simplifying assumptions which are necessary in order to apply the two methods. Particular attention has been paid to the influence of the line profile and the plasma temperature distribution. It is shown that, for conditions found in typical high-pressure light sources, some of the simplifying assumptions can be relaxed without serious loss of accuracy. Possible extension of the methods to include resonance lines has also been considered.     

The Broadening of He I lines including ion dynamic corrections,with application to λ4471Å

A theory is developed for the broadening of He I lines with forbidden components which is valid at low densities (where the forbidden line is reasonably well isolated). This theory takes into account the effects of dynamic ion broadening. Application to λ4471Å gives good agreement with experiment and with a recent calculation of Lee; reasons for agreement with Lee are discussed in detail. Comprehensive tables for 4471Å are presented. These have been extended further into the line wings than previous tabulations. Static ion theory is found to be adequate for densities greater than ～ 5 × 10¹⁵ cm^?3. A simple numerical profile for allowed lines, taking into account dynamic ion effects, is also presented.     

Correction of self-absorption spectral line and ratios of transition probabilities for homogeneous and LTE plasma

Expressions for fundamental spectral line parameters are reported for Gaussian and Lorentzian shape profiles for homogeneous plasma at equilibrium in presence of the self-absorption. These expressions for Lorentzian profiles are applied to the determination of the ratios of transition probabilities and the ratios of optical thicknesses by a new method that we propose in this article. The self-absorption is computed by spectral line profiles with a Simplex algorithm program fitting. Applications to some experimental lines illustrate the appropriate corrections.     

Spektrallinienprofile des neutralen Argons im nahen infraroten Spektralbereich

The line profiles of ArI in the infrared spectral range have been investigated. The radiances of the plasma column has been recorded on the plates using the spectrograph PGS2. For selected ArI lines the spectral distribution of intensity has been measured. The electron concentration and temperature of the plasma has been determined on the basis of the measured half width and total intensity of the hydrogen Hβ line. Using this parameter (N_e, T) the profiles for selected ArI lines have been calculated and compared with those obtained from experiment. The agreement between the theoretical and experimental profiles is satisfactory.