Vertical Profiles and Radial Locations of He II and C IV Line Emissions Observed at Different Toroidal Angles in LHD

Wang, Erhui; Morita, S.; Goto, M.; Kobayashi, M.; Dong, Chuanfei

doi:10.1585/pfr.7.2402059

Cited by 3 publications

(3 citation statements)

References 9 publications

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“…The change of the poloidal cross section of the LHD plasma within the observation region is shown for different toroidal angles of ϕ = −2 • , ϕ = 0 • and ϕ = +2 • at the top of the figure. Therefore, we can easily find a difference in the emission location between inboard and outboard X-points, when the 2D distribution is observed [57].…”

Section: Iron Impurity Transport In Ergodic Layermentioning

confidence: 94%

Effective screening of iron impurities in the ergodic layer of the Large Helical Device with a metallic first wall

et al. 2013

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In the Large Helical Device (LHD) operated with a metallic (stainless steel) first wall, it is found that the iron density, nFe, at the plasma core is fairly low (nFe ⩽ 108 cm−3) in general neutral beam (NB)-heated discharges, while the iron quickly increases with the appearance of impurity accumulation when a multi-hydrogen ice pellet is injected or the NB input power is largely reduced. Although the highest iron density (nFe ⩽ 1010 cm−3) at the plasma centre in the LHD is observed from such discharges, it suggests a still low iron concentration (nFe/ne < 10−3). Therefore, the edge iron transport in the ergodic layer, which determines the iron influx to the core plasma, is studied to clarify why the iron density in the core plasma is low. A line ratio of Fe XV located in the vicinity of the last closed flux surface to Fe VIII (or Fe IX) located in the ergodic layer decreases with density. The two-dimensional (2D) edge iron emission of Fe XVI and Fe IX is enhanced in the vicinity of the X-point with a larger number of magnetic field lines directly connected to divertor plates, which suggests that iron ions from the first wall move downstream. The density of edge Fe15+ ions giving the iron influx to the core plasma is analysed with the 2D distribution. The analysis also shows that the iron influx to the core plasma decreases with density. These results clearly indicate that the screening effect developed in the ergodic layer works well for iron ions coming from the first wall. A three-dimensional edge transport simulation with EMC3-EIRENE can also predict an effective impurity screening for heavy impurities compared to light impurities.

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Section: Iron Impurity Transport In Ergodic Layermentioning

confidence: 94%

Effective screening of iron impurities in the ergodic layer of the Large Helical Device with a metallic first wall

et al. 2013

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“…The data from about Z −385 to −390 mm are missing because a metal wire installed in the optics for the alignment of the sightlines is projected onto the corresponding position of the CCD. It is known that the spatial profile of the CIV intensity has a steep peak even in the ergodic layer of the LHD [14][15][16][17]. The edge CIV profile is fitted by a Gaussian function, as expressed by a solid line for the 500 μm slit case, and the peak intensity, the full width at half maximum, and the peak position are evaluated from the fitting curve.…”

Section: Vertical Space Resolutionmentioning

confidence: 99%

Space-resolved 3 m normal incidence spectrometer for edge impurity diagnostics in the large helical device

et al. 2014

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A space-resolved vacuum ultraviolet (VUV) spectroscopy using a 3 m normal incidence spectrometer has been developed to measure the impurity profile in the edge ergodic layer composed of stochastic magnetic field by which the edge plasma in the large helical device (LHD) is uniquely characterized. It vertically measures the spatial profile of VUV lines emitted from impurities in the wavelength range of 300-3200 Å. The wavelength interval, Δλ, which can be measured in a single discharge, is about 37 Å. A spectral resolution of 0.153 Å, which results from an entrance slit width of the spectrometer of 20 μm, is adopted. The vertical observation range, ΔZ, can be switched by taking a convex mirror in and out, which enables both the edge profile measurement focused on the ergodic layer and the full profile measurement covering an entire vertical size of the LHD plasma, e.g., 165 ≤ ΔZ ≤ 200 mm and 1000 ≤ ΔZ ≤ 1250 mm for the R(ax)=3.6 m configuration, respectively, which shows a slight wavelength dependence. Precise calibrations on the line dispersion, spectral resolution, vertical range of the observable region, and the spatial resolution have been performed with a unique method. As a preliminary result, the ion temperature profile is obtained for CIV at 1548.20 Å in the second order (denoted as 1548.20 × 2 Å) in high-density helium discharges in addition to the emission profile with a time resolution of 100 ms in a multitrack CCD operation mode. The poloidal flow in the ergodic layer based on the Doppler-shift measurement of CIV at 1548.20 × 2 Å is also observed in high-density hydrogen discharges.

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“…We applied the evaluation method of the spatial resolution by measuring the profiles of CIV 1548.20 × 2 Å emission intensity with scanning width of the slit [12]. It is known that the spatial profile of the CIV intensity has a steep peak in the ergodic layer [13][14][15][16]. As a result of scanning the slit width, the intensity increased with the slit width, while the peak position of the intensity changed inwardly and the width of the peaked profile became broader when an extremely wider slit was used.…”

Section: Development Of Diagnostics Systemsmentioning

confidence: 99%

Development of Impurity Profile Diagnostics in the Ergodic Layer of LHD using 3 m Normal Incidence VUV Spectrometer

Oishi

Morita

Dong

et al. 2013

Plasma and Fusion Research

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Space-resolved vacuum ultraviolet (VUV) spectroscopy using a 3 m normal incidence spectrometer has been developed in the large helical device (LHD) to study plasma transport in the ergodic layer by measuring the spatial profile of VUV lines from impurities emitted in the wavelength range of 300-3200 Å. Characteristics of the diagnostics system such as line dispersion, observable region and spatial resolution were evaluated. CIV spectra of 1548.20 × 2 Å were measured clearly. Intensity and ion temperature profiles were obtained simultaneously using CIV emissions in high-density discharges. Dependencies of the CIV intensity profiles on the electron density and magnetic configurations were observed.

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Vertical Profiles and Radial Locations of He II and C IV Line Emissions Observed at Different Toroidal Angles in LHD

Cited by 3 publications

References 9 publications

Effective screening of iron impurities in the ergodic layer of the Large Helical Device with a metallic first wall

Effective screening of iron impurities in the ergodic layer of the Large Helical Device with a metallic first wall

Space-resolved 3 m normal incidence spectrometer for edge impurity diagnostics in the large helical device

Development of Impurity Profile Diagnostics in the Ergodic Layer of LHD using 3 m Normal Incidence VUV Spectrometer

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