Special Issue "Plasma Spectroscopy in the Presence of Magnetic Fields"

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

Deadline for manuscript submissions: closed (30 June 2019).

Special Issue Editor

Dr. Mohammed KOUBITI
E-Mail Website
Guest Editor
Physics of Ionic and Molecular Interactions (PIIM), UMR7345, Aix-Marseille Université—CNRS, Centre Saint Jérôme, Case 232, 13397 Marseille Cedex 20, France
Interests: Plasma spectroscopy; plasma diagnostics; line-shape modeling; Stark and Zeeman effects; magnetic fusion plasmas; atomic physics; astrophysical plasmas

Special Issue Information

Dear Colleagues,

Among laboratory and astrophysical plasmas, many are subject to magnetic fields. In these so-called magnetized plasmas, magnetic fields affect the plasma constituents in a number of ways: Motion of charged particles and internal atomic structure of neutrals and ions. From the spectroscopic point of view, the presence of a magnetic field in a plasma can have different signatures on the emission line spectra depending on its strength and on the plasma conditions. This Special Issue is intended to regroup all kinds of spectroscopic techniques based on static or transient magnetic fields in magnetized plasmas and the associated progresses made in the recent years. It concerns magnetic fusion and all other magnetized plasmas such as astrophysical plasmas and high-density laser-produced ones and encompasses passive, active and plasma polarization spectroscopy. Original papers on Stark-Zeeman line broadening, Zeeman effect, motional Stark effect and related topics within the scope of Atoms are welcome.

Dr. Mohammed KOUBITI
Guest Editor

Manuscript Submission Information

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Keywords

  • Magnetized plasmas
  • Passive plasma spectroscopy
  • Active plasma spectroscopy
  • Polarization spectroscopy
  • Diagnostics based on Zeeman effect
  • Motional Stark Effect (MSE)
  • Line broadening in magnetized plasmas
  • Stark and Zeeman effects
  • Magnetic fusion plasmas
  • Astrophysical plasmas
  • High-density plasmas

Published Papers (11 papers)

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Research

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Open AccessArticle
Modeling of the Hα Emission from ADITYA Tokamak Plasmas
Atoms 2019, 7(4), 95; https://doi.org/10.3390/atoms7040095 - 05 Oct 2019
Abstract
The spatial profile of Hα spectrum is regularly measured using a high-resolution multi-track spectrometer in ADITYA tokamak to study the neutral particle behavior. The Monte Carlo neutral particle transport code DEGAS2 is used to model the experimental Hα spectral emissions. Through [...] Read more.
The spatial profile of Hα spectrum is regularly measured using a high-resolution multi-track spectrometer in ADITYA tokamak to study the neutral particle behavior. The Monte Carlo neutral particle transport code DEGAS2 is used to model the experimental Hα spectral emissions. Through the modeling of the spectral line profile of Hα, it is found that the neutral hydrogen, which is produced from molecular hydrogen and molecular hydrogen ion dissociation processes contributes 56% to the total Hα emission, and the atoms which are produced from charge-exchange process have 30% contribution. Furthermore, the experimentally measured spatial profile of chord integrated brightness was modeled for the two plasma discharges having relatively high and low density to understand the neutral particle penetration. The presence of neutrals inside the core region of the ADITYA tokamak is mainly due to the charge-exchange process. Furthermore, it is observed that neutral particle penetration is lower in higher density discharge. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Line Shapes in a Magnetic Field: Trajectory Modifictions II: Full Collision-Time Statistics
Atoms 2019, 7(4), 94; https://doi.org/10.3390/atoms7040094 - 05 Oct 2019
Abstract
In a previous paper, a variation of the Collision-time Statistics method was applied to identify the relevant perturbers for line broadening under the action of a constant magnetic field. As discussed, that version was simplified and inadequate for low magnetic field and/or large [...] Read more.
In a previous paper, a variation of the Collision-time Statistics method was applied to identify the relevant perturbers for line broadening under the action of a constant magnetic field. As discussed, that version was simplified and inadequate for low magnetic field and/or large perturber mass (ions). The purpose of the present work is to augment the previous work, so that such cases can be handed efficiently. The results may also be used to construct analytic, i.e., impact/unified models under the usual assumptions in these models. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
Open AccessArticle
Poloidal Rotation and Edge Ion Temperature Measurements Using Spectroscopy Diagnostic on Aditya-U Tokamak
Atoms 2019, 7(3), 93; https://doi.org/10.3390/atoms7030093 - 19 Sep 2019
Abstract
The impurity ion poloidal rotation and ion temperature from the Aditya-U tokamak plasma have been measured using a high-resolution spectroscopic diagnostic. It comprises of a high resolution, 1 m, f/8.7, Czerny-Turner configuration spectrometer along with charge coupled device (CCD) detector. The system [...] Read more.
The impurity ion poloidal rotation and ion temperature from the Aditya-U tokamak plasma have been measured using a high-resolution spectroscopic diagnostic. It comprises of a high resolution, 1 m, f/8.7, Czerny-Turner configuration spectrometer along with charge coupled device (CCD) detector. The system monitors the spectral line emission of C2+ impurity ions at 464.74 nm from the top port of the Aditya-U vacuum vessel with the lines of sight covering the plasma minor radius from r = 11.55 cm to 21.55 cm. The impurity ion poloidal rotation velocity and temperature have been estimated using the Doppler shift and Doppler broadening of the spectral lines respectively. The maximum poloidal rotation at a radial location of 21.55 cm in the edge of the plasma during the plasma current flat top was observed to be ~4 km/s for the analyzed discharges and the ion temperatures measured in the edge were in the range of 32–40 eV. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Evaluation of an Oxygen Transport Coefficient in the Aditya Tokamak Using the Radial Profile of O4+ Emissivity and the Importance of Atomic Data Used Therein
Atoms 2019, 7(3), 90; https://doi.org/10.3390/atoms7030090 - 09 Sep 2019
Abstract
Oxygen impurity transport in the typical discharges of the Aditya tokamak was investigated using emissivity radial profile of emissivity of the spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm from the Be-like oxygen ion. This O4+ [...] Read more.
Oxygen impurity transport in the typical discharges of the Aditya tokamak was investigated using emissivity radial profile of emissivity of the spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm from the Be-like oxygen ion. This O4+ spectral line was recorded using a 1.0 m multi-track spectrometer capable of simultaneous measurements from eight lines of sight passing through the plasma. The oxygen transport coefficients were determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional impurity transport code, STRAHL, and photon emissivity coefficient (PEC) belonging to that transition. The PEC values were obtained from both ADAS and NIFS atomic databases. Using both the databases, much higher values of diffusion coefficients compared to the neo-classical values were observed in both high and low magnetic field edge regions of typical Aditya tokamak Ohmic plasma. Although, almost similar profiles of diffusion coefficients were obtained using PEC values from both databases, the magnitude differs considerably. The maximum values of diffusion coefficients in the plasma edge at low field side of tokamak were ~45 and ~25 m2·s−1 when modeling was done using the ADAS and NIFS databases, respectively. Further analysis on the atomic data used in the calculation indicates that the difference in diffusion coefficients is mainly related to the variation in the values of atomic data of the two databases. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Spatial Profile of Neutral Temperature Measurement in Aditya-U Tokamak Plasmas
Atoms 2019, 7(3), 87; https://doi.org/10.3390/atoms7030087 - 05 Sep 2019
Abstract
The spatial profile of neutral hydrogen temperatures in Aditya-U tokamak plasma has been estimated from the spatial profile of the Hα spectral emissions measured using a high-resolution multi-track spectrometer, having a spectral resolution of 0.023 nm at a 50 μm entrance slit [...] Read more.
The spatial profile of neutral hydrogen temperatures in Aditya-U tokamak plasma has been estimated from the spatial profile of the Hα spectral emissions measured using a high-resolution multi-track spectrometer, having a spectral resolution of 0.023 nm at a 50 μm entrance slit width. The neutral temperature estimation from the Doppler broadened spectral line was carried out after considering the Zeeman effect due to the magnetic field present in the tokamak. To accurately obtain the temperature of the neutral hydrogen, two temperature components (warm and hot) were required to be considered. A code was developed to obtain the neutral temperature and is used to analyze two typical plasma discharges. The temperature of warm components varies between 3 and 5 eV, while hot atoms have temperatures in the range of 15–30 eV. It was observed that the chord-integrated neutral temperature increases slightly towards the plasma core region compared to the plasma edge of Aditya-U tokamak. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Effect of the Ions on the Electron Collision Operator through Electronic Trajectory Modification
Atoms 2019, 7(3), 77; https://doi.org/10.3390/atoms7030077 - 16 Aug 2019
Abstract
We investigate the ion effect on the broadening of the spectral line profile by the free electrons collisions with the emitters in plasmas. We only considered the weak collisions’ contribution. This effect has a consequence on the trajectories of the free electrons through [...] Read more.
We investigate the ion effect on the broadening of the spectral line profile by the free electrons collisions with the emitters in plasmas. We only considered the weak collisions’ contribution. This effect has a consequence on the trajectories of the free electrons through the electric microfield created by the ions of the plasma. Thanks to the Meijer’s functions, the calculation of the electronic Stark broadening is precisely established. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Analytical Solution of the Hanle Effect in View of CLASP and Future Polarimetric Solar Studies
Atoms 2019, 7(2), 55; https://doi.org/10.3390/atoms7020055 - 04 Jun 2019
Abstract
We have solved a problem of the Hanle effect for the hydrogen Lyman- α line in an intuitive and straightforward way. The Stokes parameters amid an anisotropic radiation field and a magnetic field are derived as an analytical formula which enables us to [...] Read more.
We have solved a problem of the Hanle effect for the hydrogen Lyman- α line in an intuitive and straightforward way. The Stokes parameters amid an anisotropic radiation field and a magnetic field are derived as an analytical formula which enables us to conduct immediate analyses of observation data taken by spectro-polarimetry. The derived formula is, in particular, supposed to be used for the analysis of the data taken by CLASP (Chromospheric Lyman-Alpha Spectro-Polarimeter), which has aimed at measuring the linear polarization in the hydrogen Lyman- α line (121.6 nm) and then evaluating the magnetic field in the upper chromosphere and the transition region. The dependence of the Stokes parameters on the strength and direction of the magnetic field and on the observation angle is derived with our analytical model. The results show a satisfactory agreement with those of a more rigorous numerical calculation where the radiative transfer is taken into account and the consistency is assured between the anisotropic randiation field and the polarized atomic state. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Line Shapes in a Magnetic Field: Trajectory Modifications I: Electrons
Atoms 2019, 7(2), 52; https://doi.org/10.3390/atoms7020052 - 27 May 2019
Abstract
In recent work, the effect of a magnetic field on the line shapes via the modification of electron perturber trajectories was considered. In the present paper we revisit this idea using a variation of the Collision-time Statistics method, in order to account for [...] Read more.
In recent work, the effect of a magnetic field on the line shapes via the modification of electron perturber trajectories was considered. In the present paper we revisit this idea using a variation of the Collision-time Statistics method, in order to account for a l l relevant perturbers. We also obtain line profiles for the hydrogen L α line for conditions of astrophysical interest. Although the Collision-time statistics method works for both electrons and ions, we apply a simplification here that results in an excessive number of ions having to be simulated. As a result, the present, simplified version, is typically only appropriate for electrons. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
On the Spatial Uniformity of the Degree of Ionization in a Helium ECR Plasma Produced under a Simple Cusp Field
Atoms 2019, 7(2), 49; https://doi.org/10.3390/atoms7020049 - 17 May 2019
Abstract
Production of a plasma that has a large degree of ionization (DOI), volume, and spatial and temporal uniformities is a challenge for the improvement of the performance of plasma-based vapor deposition processes. As a potential candidate for the discharge, we investigate plasma parameters [...] Read more.
Production of a plasma that has a large degree of ionization (DOI), volume, and spatial and temporal uniformities is a challenge for the improvement of the performance of plasma-based vapor deposition processes. As a potential candidate for the discharge, we investigate plasma parameters arising in helium electron cyclotron resonance (ECR) discharges due to a simple cusp field. Two-dimensional distributions of helium atom emission-line intensities were measured using spectroscopy with multiple viewing chords and then de-convoluted by Abel inversion. The local plasma parameters, including the atomic density, were evaluated using collisional-radiative model analysis. The DOI calculated from the electron and atomic densities reached up to 35% and, in most of the region inside the ECR surface, it was more than 10%. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Open AccessArticle
Measurement of the Magnetic Field in a Linear Magnetized Plasma by Tunable Diode Laser Absorption Spectroscopy
Atoms 2019, 7(2), 48; https://doi.org/10.3390/atoms7020048 - 15 May 2019
Cited by 1
Abstract
Tunable diode laser absorption spectroscopy (TDLAS) is a commonly used technique to measure the temperature and density of atoms or molecules in a gas. In this work, we demonstrate that the TDLAS diagnostics could be effectively applied to measure the magnetic field in [...] Read more.
Tunable diode laser absorption spectroscopy (TDLAS) is a commonly used technique to measure the temperature and density of atoms or molecules in a gas. In this work, we demonstrate that the TDLAS diagnostics could be effectively applied to measure the magnetic field in a low-density weakly magnetized plasma using the Zeeman splitting of the absorption spectrum of lines from noble gases. The laser wavelength is tailored to fit the 1 s 5 2 p 6 transition of atomic Ar with the wavelength λ = 763.51 nm . Two mechanisms of line broadening and splitting are observed: Doppler broadening and Zeeman effect. The latter is especially pronounced by applying polarization-selective observation of the absorption to the TDLAS measurements. By fitting the σ and π components of the absorption spectrum, the line-integrated magnetic field on the order of 30–50 mT is determined. The agreement between the measured values and the vacuum field (neglecting the impact of the plasma) calculations on the axis of the PSI-2 is found to be about 15–20%. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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Review

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Open AccessReview
Simulation of Spectra Code (SOS) for ITER Active Beam Spectroscopy
Atoms 2019, 7(1), 30; https://doi.org/10.3390/atoms7010030 - 01 Mar 2019
Cited by 2
Abstract
The concept and structure of the Simulation of Spectra (SOS) code is described starting with an introduction to the physics background of the project and the development of a simulation tool enabling the modeling of charge-exchange recombination spectroscopy (CXRS) and associated passive background [...] Read more.
The concept and structure of the Simulation of Spectra (SOS) code is described starting with an introduction to the physics background of the project and the development of a simulation tool enabling the modeling of charge-exchange recombination spectroscopy (CXRS) and associated passive background spectra observed in hot fusion plasmas. The generic structure of the code implies its general applicability to any fusion device, the development is indeed based on over two decades of spectroscopic observations and validation of derived plasma data. Four main types of active spectra are addressed in SOS. The first type represents thermal low-Z impurity ions and the associated spectral background. The second type of spectra represent slowing-down high energy ions created from either thermo-nuclear fusion reactions or ions from injected high energy neutral beams. Two other modules are dedicated to CXRS spectra representing bulk plasma ions (H+, D+, or T+) and beam emission spectroscopy (BES) or Motional Stark Effect (MSE) spectrum appearing in the same spectral range. The main part of the paper describes the physics background for the underlying emission processes: active and passive CXRS emission, continuum radiation, edge line emission, halo and plume effect, or finally the charge exchange (CX) cross-section effects on line shapes. The description is summarized by modeling the fast ions emissions, e.g., either of the α particles of the fusion reaction or of the beam ions itself. Full article
(This article belongs to the Special Issue Plasma Spectroscopy in the Presence of Magnetic Fields)
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