Localized tungsten deposition in divertor region in JT-60U

Ueda, Y.; Fukumoto, M.; Watanabe, Jun; Ohtsuka, Y.; Arai, Takashi; Asakura, N.; Nobuta, Y.; Sato, Masahiro; Nakano, T.; Yagyu, J.; Ochiai, Kentaro; Takakura, Kei; Tanabe, T.

doi:10.1088/0029-5515/49/6/065027

Cited by 25 publications

(22 citation statements)

References 16 publications

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“…1. This numerical grid is produced from a JT-60U tungsten experiment configuration [13] (shot #49540). The toroidal magnetic field B 0 value at the geometrical center of plasma is 3.6 T. The plasma current I p is 1.6 MA.…”

Section: Geometrical Model and Basic Plasma Parametersmentioning

confidence: 99%

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Effects of Classical and Neo‐classical Cross‐field Transport of Tungsten Impurity in Realistic Tokamak Geometry

Yamoto

Homma

Inoue

et al. 2016

Contrib. Plasma Phys.

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The initial simulation study of the neoclassical perpendicular self-diffusion transport in the SOL/Divertor regions for a realistic tokamak geometry with the IMPGYRO code has been performed in this paper. One of the most unique features of the IMPGYRO code is calculating exact Larmor orbit of the test particle instead of assuming guiding center approximation. Therefore, effects of the magnetic drifts in realistic tokamaks are naturally taken into account in the IMPGYRO code. This feature makes it possible to calculate neoclassical transport processes, which possibly become large in the SOL/divertor plasma. Indeed, neoclassical self-diffusion process, the resultant effect of the combination of magnetic drift and Coulomb collisions with background ions, has already been included in the IMPGYRO model. In the present paper, prior to implementing the detailed model of neoclassical transport process into IMPGYRO, we have investigated the effect of neoclassical selfdiffusion in a realistic tokamak geometry with lower single null X-point. We also use a model with guiding center approximation in order to compare with the IMPGYRO full orbit model. The preliminary calculation results of each model have shown differences in the perpendicular average velocity of impurity ions at the top region of the SOL. The mechanism which leads to the difference has been discussed.

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Section: Geometrical Model and Basic Plasma Parametersmentioning

confidence: 99%

“…Tungsten impurities are launched from the outer divertor plate 1.4 cm outside from the separatrix. The location where the tungsten plates have been installed in the JT-60U tungsten experiments [13] has been considered as the initial position of tungsten impurities.…”

Section: Impgyro Calculation Setupsmentioning

confidence: 99%

Effects of Classical and Neo‐classical Cross‐field Transport of Tungsten Impurity in Realistic Tokamak Geometry

Yamoto

Homma

Inoue

et al. 2016

Contrib. Plasma Phys.

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“…Tungsten impurities are launched from the outer divertor plate 1.4 cm outside from the separatrix, where the tungsten plates have been installed in the JT-60U tungsten experiments [4], with constant generation rate of 10 18 /s. Monotonic energy distribution function with 10 eV has been assumed.…”

Section: Impgyro Calculation Setupsmentioning

confidence: 99%

Systematic Study of Tungsten Impurity Transport in Representative Regimes of Divertor Plasma

Yamoto

Hoshino

Toma

et al. 2014

Contrib. Plasma Phys.

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The tungsten impurity transport has been studied by IMPGYRO code for a model tokamak geometry of JT-60U tungsten experiments. The background plasma profiles calculated from SOLPS has been used. The density profiles of tungsten are compared between the low background deuterium density (Case A:−3 at core side boundary) and the high background deuterium density (Case B: n D + = 3.0 × 10 19 m −3 at core side boundary). In both cases, flow reversal in the SOL has been observed. The impurity density profile in the SOL is more localized for Case B. These features are possibly explained by the force balance between the thermal force and the friction force.

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“…Tungsten coated tiles exposed to the divertor plasmas in JT-60U and ASDEX Upgrade have been analyzed to investigate the effects of carbon on hydrogen retention. In these tokamaks, tungsten-coated tiles were installed to investigate feasibility of tungsten as the PFCs, for example, tungsten accumulation and its suppression in the core plasmas [5,6], tungsten migration [7,8] and in-vessel deuterium retention [9]. After experimental campaigns, a part of the tungsten-coated tiles were taken out and deuterium and carbon accumulation in the tungsten coating layers were investigated [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Chemical Binding States of Carbon Atoms Migrated in Tungsten Coating Layer Exposed to JT-60U Divertor Plasmas

Fukumoto

Nakano

Ueda

et al. 2013

Plasma and Fusion Research

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Carbon migration in the tungsten coating layer exposed to JT-60U divertor plasmas has been investigated by analysis of chemical binding states of the carbon atoms. More than 1% of carbon atoms were accumulated as graphitic carbon, amorphous carbon and/or carbon-deuterium bonds. This concentration was more than five orders of magnitude higher than the solubility of carbon atoms in tungsten lattice. Up to 20% of ditungsten carbide (W 2 C) was also formed in the tungsten coating layer. These findings suggested the following carbon migration mechanism in the tungsten coating layer. The incident carbon migrates along grain boundaries and defects such as pores over the depth which is evaluated by the carbon diffusion coefficient in tungsten lattice. The carbon atoms trapped on grain surface penetrate and diffuse in the grains. The carbon atoms exceeded the solubility of carbon atoms in tungsten lattice chemically bind to tungsten atoms and form W 2 C.

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Localized tungsten deposition in divertor region in JT-60U

Cited by 25 publications

References 16 publications

Effects of Classical and Neo‐classical Cross‐field Transport of Tungsten Impurity in Realistic Tokamak Geometry

Effects of Classical and Neo‐classical Cross‐field Transport of Tungsten Impurity in Realistic Tokamak Geometry

Systematic Study of Tungsten Impurity Transport in Representative Regimes of Divertor Plasma

Chemical Binding States of Carbon Atoms Migrated in Tungsten Coating Layer Exposed to JT-60U Divertor Plasmas

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