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11 pages, 2464 KiB

Open AccessArticle

Modeling of the H_α Emission from ADITYA Tokamak Plasmas

by Ritu Dey, Malay B. Chowdhuri, Joydeep Ghosh, Ranjana Manchanda, Nandini Yadava, Umeshkumar C. Nagora, Parveen K. Atrey, Jayesh V. Raval, Y. Shankara Joisa, Rakesh L. Tanna and ADITYA Team

Atoms 2019, 7(4), 95; https://doi.org/10.3390/atoms7040095 - 5 Oct 2019

Cited by 3 | Viewed by 3115

Abstract

The spatial profile of H_α 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 H_α spectral emissions. Through [...] Read more.

The spatial profile of H_α 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 H_α spectral emissions. Through the modeling of the spectral line profile of H_α, it is found that the neutral hydrogen, which is produced from molecular hydrogen and molecular hydrogen ion dissociation processes contributes 56% to the total H_α 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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10 pages, 2413 KiB

Open AccessArticle

Poloidal Rotation and Edge Ion Temperature Measurements Using Spectroscopy Diagnostic on Aditya-U Tokamak

by Gaurav Shukla, Malay B. Chowdhuri, Kajal Shah, Nandini Yadava, Ranjana Manchanda, Kumarpalsinh A. Jadeja, Rakesh L. Tanna, Balamurali Krishna Mayya K., Joydeep Ghosh and Aditya-U Team

Atoms 2019, 7(3), 93; https://doi.org/10.3390/atoms7030093 - 19 Sep 2019

Cited by 5 | Viewed by 3218

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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10 pages, 1599 KiB

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

by Malay Bikas Chowdhuri, Joydeep Ghosh, Ritu Dey, Sharvil Patel, Nandini Yadava, Ranjana Manchanda, Amrita Bhattacharya, Izumi Murakami and Aditya Team

Atoms 2019, 7(3), 90; https://doi.org/10.3390/atoms7030090 - 9 Sep 2019

Cited by 4 | Viewed by 2816

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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9 pages, 1983 KiB

Open AccessArticle

Spatial Profile of Neutral Temperature Measurement in Aditya-U Tokamak Plasmas

by Nandini Yadava, Joydeep Ghosh, Malay Bikas Chowdhuri, Ranjana Manchanda, Sripathi Punchithaya K, Ritu Dey, Kumarpalsinh A. Jadeja, Rakesh L. Tanna, Deepti Tripathi and Aditya-U Team

Atoms 2019, 7(3), 87; https://doi.org/10.3390/atoms7030087 - 5 Sep 2019

Cited by 1 | Viewed by 3140

Abstract

The spatial profile of neutral hydrogen temperatures in Aditya-U tokamak plasma has been estimated from the spatial profile of the H_α 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 H_α 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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11 pages, 278 KiB

Open AccessArticle

Effect of the Ions on the Electron Collision Operator through Electronic Trajectory Modification

by Yasmina Ben Nana, Fethi Khelfaoui, Said Douis, Eshrat Sadeghzadeh Lari and Mohammed Tayeb Meftah

Atoms 2019, 7(3), 77; https://doi.org/10.3390/atoms7030077 - 16 Aug 2019

Cited by 1 | Viewed by 2813

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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12 pages, 1366 KiB

Open AccessArticle

Analytical Solution of the Hanle Effect in View of CLASP and Future Polarimetric Solar Studies

by Motoshi Goto, Ryohko Ishikawa, Yusuke Iida and Saku Tsuneta

Atoms 2019, 7(2), 55; https://doi.org/10.3390/atoms7020055 - 4 Jun 2019

Cited by 1 | Viewed by 3158

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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12 pages, 607 KiB

Open AccessArticle

Line Shapes in a Magnetic Field: Trajectory Modifications I: Electrons

by Spiros Alexiou

Atoms 2019, 7(2), 52; https://doi.org/10.3390/atoms7020052 - 27 May 2019

Cited by 14 | Viewed by 3054

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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6 pages, 1251 KiB

Open AccessArticle

On the Spatial Uniformity of the Degree of Ionization in a Helium ECR Plasma Produced under a Simple Cusp Field

by Akira Ueda, Taiichi Shikama, Yohei Iida and Masahiro Hasuo

Atoms 2019, 7(2), 49; https://doi.org/10.3390/atoms7020049 - 17 May 2019

Viewed by 2890

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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Review

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27 pages, 6135 KiB

Open AccessReview

Simulation of Spectra Code (SOS) for ITER Active Beam Spectroscopy

by Manfred von Hellermann, Maarten de Bock, Oleksandr Marchuk, Detlev Reiter, Stanislav Serov and Michael Walsh

Atoms 2019, 7(1), 30; https://doi.org/10.3390/atoms7010030 - 1 Mar 2019

Cited by 21 | Viewed by 5339

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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