Studies of the structure of C pellet ablation clouds in W7-AS

Bakhareva, O. A.; Sergeev, V. Yu.; Kuteev, B. V.; Skokov, V. G.; Timokhin, V. M.; Burhenn, R.; Team, W As

doi:10.1134/1.1904144

Cited by 8 publications

(7 citation statements)

References 5 publications

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“…The assumption of LTE populations for those levels implicitly includes such processes. Therefore, the direct ionization and recombination processes are omitted in equation (14). The level populations which are assumed to be in LTE are fixed at the values evaluated by equation ( 2) with the derived T e and n e .…”

Section: Discussionmentioning

confidence: 99%

“…When the plasmas are optically thick, however, A(p, q) should actually be approximated as A(p, q) 0 (p, q) in equation (14), where 0 (p, q) is the escape factor for the corresponding transition. Since 0 (p, q) depends on the lower level population n z (q), equation ( 14) becomes nonlinear.…”

Section: Discussionmentioning

confidence: 99%

“…With regard to the experimental study of pellet ablation, most measurements have focused on taking pictures of ablation clouds through an interference filter at the wavelength of a certain emission line. Pellet trajectories and cloud shapes have been derived from such pictures [1,2,7,11,14]. With this kind of measurement, however, it is difficult to investigate the detailed atomic processes in the ablation cloud.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic study of a carbon pellet ablation cloud

Goto¹,

Morita²,

Koubiti³

2010

J. Phys. B: At. Mol. Opt. Phys.

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Carbon pellets were injected into high-temperature plasmas produced in the Large Helical Device (LHD), a heliotron-type fusion experimental device. Radiation from a high-density plasma formed around the pellet core, the so-called ablation cloud, was observed and its spectrum in the UV-visible wavelength range was obtained. The observed spectrum is found to be dominated by emission lines of CII and CIII ions, and their level populations are determined from the measured line intensities. The result suggests that LTE (local thermodynamic equilibrium) is established over the measured excited levels for both ions, and the electron temperature is determined to be 2.5 eV and 3.0 eV for the CII and CIII ions, respectively, on the assumption that level populations follow a Boltzmann distribution. For the plasma dominated by the CII lines, the electron density, n e = 6.5 × 10 22 m −3 , and plasma volume, V = 5.3 × 10 −6 m 3 , are simultaneously derived from a fit of the CII λ 723 nm ([1s 2 2s 2 ]3p 2 P o -3d 2 D) line profile which is subject to various broadening effects such as Stark broadening. For the plasma dominated by CIII lines, V = 4.5 × 10 −2 m 3 is derived from an analysis of the reabsorption effect appearing in fine structure lines of the CIII λ 117 nm ([1s 2 ]2s2p 3 P o -2p 2 3 P) transition. The assumption of electric charge neutrality in the ablation cloud yields n e = 4.7 × 10 20 m −3 . These results suggest such a structure in the ablation cloud that a dense plasma dominated by the CII lines is surrounded by a larger and lower density plasma which is responsible for the CIII lines. The assumption of complete LTE for CIII levels, which is used in the analysis, is shown to be approximately true with the help of collisional-radiative model calculations, for which the reabsorption effect is taken into account. Thus, in this study various plasma parameters in the ablation cloud are determined and information about the cloud structure is obtained.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spectroscopic study of a carbon pellet ablation cloud

Goto¹,

Morita²,

Koubiti³

2010

J. Phys. B: At. Mol. Opt. Phys.

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“…Figure 2(a) shows the results of calculating the lithium dust ablation rate evaluated on the basis of the neutral gas shielding model [20] for the 90 m s −1 velocity and the 150 µm diameter of the droplet at ITER conditions. It is seen that the droplet penetrates at a plasma radius r/a ≈ 0.99.…”

Section: Particle Balance Equationsmentioning

confidence: 99%

Conceptual analysis of a tokamak reactor with lithium dust jet

Kuteev¹,

Sergeev²,

Krylov³

et al. 2010

Nucl. Fusion

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The steady state operation of tokamak reactors requires re-radiating a substantial part of the fusion energy dissipated in plasma to make the heat loads onto the first wall more uniform and to reduce the erosion of divertor plates. One of the approaches realizing this goal uses injection of lithium dust jet into the scrape-off layer. In this paper a quantitative conceptual analysis of the reactor parameters with lithium dust jet injection is presented. The effects of the lithium on the core and SOL plasma are considered. The first results of developing the lithium jet injection technology and its application on T-10 tokamak are also presented.

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“…With an assumption that intensity of line emissions from the ablation cloud is proportional to the ablation rate, trajectory of the pellet or shape of the clouds is deduced from the temporal variation of the emission intensity [4][5][6][7][8]. Detailed information about atomic processes taking place in the ablation cloud is necessary for more quantitative understanding of the ablation mechanism.…”

Section: Introductionmentioning

confidence: 99%

Plasma Spectroscopy on an Aluminum-Pellet Ablation Cloud in an LHD Plasma with an Echelle Spectrometer

Fujii

Shikama

Morita

et al. 2020

Atoms

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We developed an echelle spectrometer for the simultaneous observation of the whole visible range with a high instrumental resolution, for example, 0.055 nm (full width at the half maximum) at 400 nm and 0.10 nm at 750 nm. With the spectrometer, the emission from an ablation cloud of an aluminum pellet injected into a high-temperature plasma generated in the Large Helical Device (LHD) was measured. We separated the emission lines into Al I, II, III and IV groups, and estimated the electron temperature and density of the ablation cloud from the line intensity distribution and Stark broadening respectively, of each of the Al I, II and III groups. We also determined the Stark broadening coefficients of many Al II and III lines from the respective Stark widths with the estimated electron temperature and density.

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Studies of the structure of C pellet ablation clouds in W7-AS

Cited by 8 publications

References 5 publications

Spectroscopic study of a carbon pellet ablation cloud

Spectroscopic study of a carbon pellet ablation cloud

Conceptual analysis of a tokamak reactor with lithium dust jet

Plasma Spectroscopy on an Aluminum-Pellet Ablation Cloud in an LHD Plasma with an Echelle Spectrometer

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