Special Issue "Spectral Line Shapes in Plasmas"


A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (31 March 2014)

Special Issue Editors

Guest Editor
Dr. Evgeny Stambulchik
Plasma Laboratory, Weizmann Institute of Science, Rehovot 7610001 Israel
Website: http://plasma-gate.weizmann.ac.il/people/stambulchik-evgeny/
E-Mail: Evgeny.Stambulchik@weizmann.ac.il
Phone: 972-8-9343610
Fax: 972-8-9343491
Interests: line-shape broadening in plasmas; Stark and Zeeman effects; polarization spectroscopy; non-LTE kinetics in plasmas

Guest Editor
Dr. Hyun-Kyung Chung
International Atomic Energy Agency, Atomic and Molecular Data Unit, Nuclear Data Section, P.O. Box 100, A-1400 Vienna, Austria
E-Mail: h.chung@iaea.org
Phone: +43 1 2600 21729
Fax: +43 1 26007
Interests: atomic, molecular and plasma-surface interaction data for fusion applications; atomic processes in plasmas; non-LTE kinetics in plasmas; radiative properties of hot dense matter; plasma spectroscopy modeling

Guest Editor
Dr. Annette Calisti
Laboratoire PIIM, UMR7345,Aix-Marseille Université - CNRS,Centre Saint Jérôme case 232, 13397 Marseille Cedex 20, France
E-Mail: annette.calisti@univ-amu.fr
Phone: +33(0)491282719

Guest Editor
Dr. Manuel Á. González Delgado
Departamento de Física Aplicada, Escuela Técnica Superior de Ingeniería Informática, Universidad de Valladolid, Paseo de Belén 15, 47011 Valladolid, Spain
E-Mail: manuelgd@termo.uva.es
Interests: atomic line shape calculation; plasma diagnostics; computer simulation; mLearning; biometrics

Special Issue Information

Line-shape analysis is one of the most important tools for diagnostics of both laboratory and space plasmas. Its reliable implementation requires sufficiently accurate calculations, which imply the use of analytical methods and computer codes of varying complexity, and, necessarily, varying limits of applicability and accuracy. However, studies comparing different computational and analytical methods are almost nonexistent. The Spectral Line Shapes in Plasma (SLSP) code comparison workshop series was established to fill this gap.

Numerous computational cases considered in the two workshops organized to date (in 2012 and 2013) not only served the purpose of code comparison, but also have applications in research of magnetic fusion, astrophysical and laser-produced plasmas, and more. Therefore, although the first workshop was shortly reviewed elsewhere[1], and will likely be followed by a review of the second one, it was unanimously decided by the participants that a dedicated volume devoted to results of the workshops is desired. It is the purpose of this special issue.

In addition, we welcome contributions from the wider community working on diverse aspects of calculations of spectral line shapes in plasmas.

[1] E. Stambulchik, High Energy Density Phys. 9, 528-534 (2013).


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spectral line shapes; line broadening; Stark effect; Zeeman effect; code comparison

Published Papers

No papers have been published in this special issue yet, see below for planned papers.

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Influence of Micro-Fields Directionality on Line Shapes
Authors: A. Calisti 1, A. Demura 2, M. Gigosos 3 , D. González-Herrero 3, V. Lisitsa 2, E. Stambulchik 4
Affiliations: 1 PIIM, Aix-Marseille Université - CNRS, Campus St Jérôme, Marseille, France; 2 Russian Research Center Kurchatov, Moscow, Russia; 3 Departamento de Óptica, Universidad de Valladolid, Valladolid, Spain; 4 Faculty of Physics, Weizmann Institute of Science, Rehovot, Israel

Abstract: The effect of ionic field fluctuations on spectral line shapes of hydrogen and hydrogen-like emitters has been studied for a long time by different groups. In the 1970s, the observed deviations between experiments and theories were attributed to ion motion. At the same time, the first attempts to include ion motion effects in theories appeared [1–4] and the experimental proof on hydrogen has been obtained nearly concomitantly by Wiese and co-workers [5]. The first N-body molecular dynamics simulations appeared in the early 1980s [6]. In the framework of the Spectral Line Shapes in Plamas Code Comparison Workshop (SLSP) [7], large discrepancies appeared between the different approaches to account for ion motion effects in spectral line shape calculations. For a better understanding of these effects, in the second edition of the SLSP in August 2013, two cases were dedicated to the study of the ionic field directionality on line shapes. In this paper, the effects of the direction and magnitude fluctuations are separately analyzed. To this end, ”rotational” and ”vibrational” micro-fields have been defined such as:

Frot(t) = F0 F(t)/|F(t)|


Fvib(t) = nz|F(t)|

with F0 the Holtsmark field and F(t) the field created at the emitter by the surrounding charges (protons) interacting through a Debye screened Coulomb potential. The effects of these two variants of electric field models together with the effects of F(t) on spectral line shapes are discussed on the He II Lyman-α and -β lines for different densities and temperatures.

[1] Dufty, J. Phys. Rev. A 1970, 2(2).
[2] Frisch, U.; Brissaud, A. J.Q.S.R.T. 1971, 11(12); Brissaud, A.; Frisch, U. J.Q.S.R.T. 1971 11(12).
[3] Hey, J.D.; Griem, H.R. Phys. Rev. A 1975, 12, 169.
[4] Demura, A.V.; Lisitsa, V.S.; Sholin, G.V. Sov. Phys. JETP 1977, 46(2).
[5] Kelleher, D.E.; Wiese, W.L. Phys. Rev. Lett. 1973, 31 ; Wiese, W.L.; Kelleher, D.E., V. Helbig, Phys. Rev. A 1975, 11.
[6] Stamm, R.; Voslamber, D., J.Q.S.R.T. 1979, 22(599).
[7] Stambulchik, E. High Energy Density Physics 2013, 9(528). Available online at http://plasma-gate.weizmann.ac.il/slsp/.


Title: Spectral-Kinetical and Statistical-Dynamical Couplings in Stark Broadening
Author: A.V. Demura
Affiliation: National Research Center “Kurchatov institute”, Moscow, Russia

Abstract: The article is devoted to general problems in Stark broadening of spectral lines by plasmas. It is related to inadequacy of standard reduced simplified descriptions, when it is supposed that the density matrix is diagonal while the plasma microfield dynamics is unchangeable for any frequency detuning from the line center. These general concepts are illustrated in more detail by consideration of several problems. The contradiction of the achievements of current computer simulations with the general thesis, that the searched result could be given by the equilibrium thermodynamical average, is outlined and discussed as well.


Title: Hydrogen Line Shape Formation in Thermonuclear Reactor Plasma
Authors: V.S. Lisitsa, M.B. Kadotsev, V.A. Shurygin, V. A. Neverov
Affiliation: National Research Center “Kurchatov Institute”, Moscow, Russia

Abstract: Spectroscopic diagnostics of plasma based on Balmer lines of hydrogen isotopes is adopted as one of the main diagnostics in ITER. The main goals of the diagnostics are determination of neutral-atom fluxes from the reactor wall as well as the isotope ratio (deuterium to tritium) during reactor operation. In the present study we describe briefly problems related to the line-shape formation in SOL plasma corresponding mostly to observations along the horizontal chord. The SOL domain is related to relatively low electron densities (1012–1013 cm–3) and high temperatures (30 eV up to 1 keV). The main effects responsible for the line-shape formation in SOL are Doppler and Zeeman effects. The main problem is in a correct determination of the neutral velocity distribution function. The function is determined by a number of atomic processes, namely: molecular dissociation, ionization and charge exchange of neutral atoms on plasma ions, electron excitation accompanied by charge exchange from atomic excited states, and atom reflection from the wall. All the processes take place step by step during atom motion from the wall to the plasma center. In practice, the largest contribution to the atom radiation comes from a thin lower near the wall with typical size 10–30 cm, which is small as compared with minor ITER radius (2 m). The important problem is a strongly non-uniform distribution of plasma parameters (electron and ion densities and temperatures). The distributions change along different observation hordes and ITER working regimes.

There are a number of problems for the theoretical treatment of hydrogen line shapes in the SOL domain of ITER. The first one is a correct calculation of the neutral velocity distribution function. Then, calculation of Zeeman–Doppler line shapes along the observation chord, with account of plasma parameters distributions determining the intensity of radiation from a specific horde point. Finally, one needs to extract information about D–T composition from the signal integrated along the chord, that is, to solve the inverse problem of the local signal reconstruction with account for strong overlapping of the isotope line shapes.

In the present report, most attention is devoted to the problem of the velocity distribution function calculations. The most correct method for the problem solution is application of Monte Carlo method for atom motion near the wall. At the same time, the method is too complicated to be combined with other numerical methods for plasma modeling and for different regimes of operation. Thus, it is important to develop simpler methods for neutral distribution in space and velocities. The efficiency of such methods has to be tested by comparison with Monte Carlo codes for specific plasma conditions.

A new simplified method for description of neutral penetration into plasma is suggested. The method is based on the ballistic motion of neutrals along the line of sight in the forward–back approximation, well-known in radiation transport theory. As a result, the two dimensional distribution function, depending on line-of-sight coordinate and the velocity projection on the line responsible for the Doppler broadening, will be calculated. The comparison of the method with Monte Carlo calculations confirms the high precision of the ballistic model.


Title: Ideal Coulomb Plasma Approximation in Line Shape Models:Problematic Issues
Authors: J. Rosato *, H. Capes, and R. Stamm
Affiliation: Laboratoire PIIM, UMR 7345 Université d’Aix-Marseille / CNRS, Centre de Saint-Jérôme, Case 232, F-1339, Marseille Cedex 20, France; E-mail: joel.rosato@univ-amu.fr

Abstract: The Spectral Line Shapes in Plamas Code Comparison Workshop (SLSP) focuses on a set of standardized physical problems to be addressed using codes from different research groups/labs. Amongst these problems is the description of Stark line shapes with ion dynamics effects, referred to as the cases “1” and “2” in the first (2012) and second (2013) editions of the Workshop. In order to get a simple interpretation of what the codes effectively calculate, a set of idealizing assumptions has been considered. For example, the electrons and the ions are assumed to move along straight path trajectories and they produce unscreened Coulomb potentials (ideal plasma approximation). The purpose of this paper is to show that the latter assumption raises a problem of consistency in the interpretation of ab initio numerical simulations, i.e., simulations that are free from physical approximations in the evaluation of the plasma microfield and in the calculation of the atomic dipole autocorrelation function. They commonly serve as a reference for testing other models. Although very convenient in practice (in particular for programming purposes), the simulations can take a long time and become useless in the case where a large number of particles are required in the evaluation of the microfield. This occurs for weakly coupled plasmas, when the Debye length is much larger than the mean interparticle distance. A relevant strategy when performing a simulation is to take a box (either of a cubic, spherical, or more complex shape) of characteristic size of the order of the Debye length (typically larger by a factor of several units), which means that the number of particles can be very large in weakly coupled plasma conditions. If the plasma is so weakly coupled that a calculation cannot be performed on a reasonable time scale, the box size is reduced and the corresponding number of particles is adjusted in such a way that a relevant statistical quantity (like the microfield probability density function) is well reproduced within a few percentage error bars. We suggest that this procedure does not suffice to obtain reference profiles. Our argument is based on the use of an analytical model for Stark broadening in regimes such that the impact approximation is not far from being satisfied by the perturbers under consideration (ions or electrons) [1]. We apply it to the Lyman a line broadened due to the electrons at N = 1017 cm–3 and T = 100 eV (subcase “” of the 2013 SLSP), using an unscreened Coulomb electric field as required in the Workshop statement of cases. The resulting profile is about twice larger than that obtained from simulations, suggesting that the latter underestimate the Stark broadening because too small a box is used. The relevance of using a Coulomb electric field can be questioned because it implies taking an infinite Debye length and, accordingly, a box of infinite size in a simulation. With an analysis of our model, we suggest that there exists a natural length scale proper to the line under consideration which can serve for a setting of the box size.

[1] J. Rosato, H. Capes, and R. Stamm, Phys. Rev. E 86, 046407 (2012); Phys. Rev. E 88, 035101 (2013)


Title: Review of Isolated Lines: Li-Like 2s-2p Code Comparisons
Author: Spiros Alexiou
Affiliation: University of Crete, TETY, 71409 Heraklion, TK 2208, Greece

Abstract: In this work we briefly summarize theoretical aspects of isolated line broadenining and present and discuss test run comparisons from different participating lineshape codes for the 2s-2p transition for LiI, BIII and NV.

Last update: 25 November 2013

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