Erosion of tungsten and carbon markers in the outer divertor of ASDEX-Upgrade

Mayer, M.; Rohde, V.; Ramos, Gustavo; Vainonen-Ahlgren, E.; Likonen, J.; Chen, J L

doi:10.1088/0031-8949/2007/t128/021

Cited by 43 publications

(48 citation statements)

References 17 publications

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“…The maximum W erosion at the outer strike point is about 7×10 14 W-atoms/cm 2 s = 0.1 nm/s. This is comparable to the observed erosion of W markers in the carbon divertor during the 2004-2005 operational phase, which was >0.06 nm/s [3]. The lowest few cm of tile 1 (close to the corner with tile 10) show a small deposition area.…”

Section: Net Tungsten Erosion and Redepositionsupporting

confidence: 79%

“…This indicates a very inhomogeneous erosion of the W marker, with a maximum erosion at plasma exposed areas which is more than 5 times larger than the mean erosion of the layer. Such an inhomogeneous erosion was already observed at tungsten marker layers in the outer divertor of JET [23], and in previous campaigns with marker layers in the outer divertor of ASDEX Upgrade [3]. This inhomogeneous erosion is difficult to understand, because the Larmor radius of both impurity and deuterium ions is larger than 100 µm: This is much larger than the surface roughness of a few µm, so that for the gyrating ions the surface should appear almost smooth.…”

Section: Morphology Of Erosion Areas In the Outer Divertormentioning

confidence: 65%

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Tungsten erosion and redeposition in the all-tungsten divertor of ASDEX Upgrade

et al. 2009

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Net erosion and deposition of tungsten in the ASDEX Upgrade divertor were determined after the 2007 campaign by using thin tungsten marker stripes. ASDEX Upgrade had full-tungsten plasmafacing components during this campaign. The inner divertor and the roof baffle were net W deposition areas with a maximum deposition of about 1×10 18 W-atoms/cm 2 in the private flux region below the inner strike point. Net erosion of W was observed in the whole outer divertor, with the largest erosion close to the outer strike point. Only a small fraction of the tungsten eroded in the main chamber and in the outer divertor was found in redeposits in the inner divertor, while a large fraction was either redeposited at unidentified places in the main chamber or has formed dust.

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Section: Net Tungsten Erosion and Redepositionsupporting

confidence: 79%

Section: Morphology Of Erosion Areas In the Outer Divertormentioning

confidence: 65%

Tungsten erosion and redeposition in the all-tungsten divertor of ASDEX Upgrade

et al. 2009

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“…The erosion pattern visible in Fig 1 is very inhomogeneous: On the leading surface areas the W layer is complete eroded exposing the underlying C substrate, while on the shadowed surface areas the W layer is still intact. Such an inhomogeneous erosion pattern was already previously observed at the outer divertor of AUG [2], and was also observed in the outer JET divertor [3]. There is a slight tilt angle ∕ = 90 ∘ between the rows of leading surfaces and the magnetic field direction which already hints towards the influence of E×B forces on the particle trajectories responsible for eroding the W at these leading surfaces.…”

Section: Experimental Erosion Patterns On W Coated Csupporting

confidence: 74%

Impact of gyro-motion and sheath acceleration on the flux distribution on rough surfaces

Schmid¹,

Mayer²,

Adelhelm³

et al. 2010

Nucl. Fusion

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Abstract.As was already observed experimentally, the erosion of tungsten (W) coated graphite (C) tiles in ASDEX-Upgrade exhibit regular erosion patterns on the m rough surfaces who's origin is not fully understood: Surfaces inclined towards the magnetic field direction show strong net W erosion while surfaces facing away from the magnetic field are shadowed from erosion and may even exhibit net W deposition. This paper presents a model which explains the observed erosion/deposition pattern. It is based on the calculation of ion trajectories dropping through the plasma sheath region to the rough surface with combined magnetic and electrical fields. The surface topography used in the calculations is taken from AFM measurement of real ASDEX-Upgrade tiles. The calculated erosion patterns are directly compared to SEM images of the erosion zones from the same location. The erosion on surfaces inclined towards the magnetic field is due to ions from the bulk plasma which enter the sheath gyrating along the magnetic field lines, while the deposition of W on surfaces facing away from the magnetic field is due to promptly re-deposited W that is ionized still within the magnetic pre-sheath.

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“…The Deuterium Inventory in ASDEX Upgrade 2002 2003 tiles, and in addition a tungsten marker stripe [9]. For the sake of better readability we use the tile numbers as shown in Fig.…”

Section: Analyzed Samplesmentioning

confidence: 99%

“…Most of the outer divertor is a net erosion area for carbon and tungsten [7,9], and surface temperatures can get higher than in the inner divertor. Consequently the deuterium retention in the outer divertor is small.…”

Section: Deuterium Inputmentioning

confidence: 99%

The deuterium inventory in ASDEX Upgrade

et al. 2007

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Abstract. The deuterium inventory in ASDEX Upgrade was determined by quantitative ion beam analysis techniques and SIMS for di erent discharge campaigns between the years 2002 and 2005. ASDEX Upgrade was a carbon dominated machine during this phase. Full poloidal sections of the lower and upper divertor tile surfaces, limiter tiles, gaps between divertor tiles, gaps between inner heat shield tiles, and samples from remote areas below the roof ba e and in pump ducts were analyzed, thus o ering an exhaustive survey of all relevant areas in ASDEX Upgrade. Deuterium is mainly trapped on plasma exposed surfaces of inner divertor tiles, where about 70% of the retained deuterium inventory are found. About 20% of the inventory are retained at or below the divertor roof ba e, and about 10% are observed in other areas, such as the outer divertor and in gaps between tiles. The long term deuterium retention is 3 4% of the total deuterium input. The obtained results are compared to gas balance measurements, and conclusions about tritium retention in ITER are made.

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Erosion of tungsten and carbon markers in the outer divertor of ASDEX-Upgrade

Cited by 43 publications

References 17 publications

Tungsten erosion and redeposition in the all-tungsten divertor of ASDEX Upgrade

Tungsten erosion and redeposition in the all-tungsten divertor of ASDEX Upgrade

Impact of gyro-motion and sheath acceleration on the flux distribution on rough surfaces

The deuterium inventory in ASDEX Upgrade

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