Erosion and redeposition patterns on entire erosion marker tiles after exposure in the first operation phase of WEST

Balden, M.; Mayer, M.; Bliewert, B.; Bernard, E.; Diez, M.; Firdaouss, M.; Missirlian, M.; Pégouriè, B.; Richou, M.; Roche, Hélène; Tsitrone, E.; Martin, Céline; Hakola, A.

doi:10.1088/1402-4896/ac2182

Cited by 28 publications

(36 citation statements)

References 35 publications

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“…With the full-W ASDEX Upgrade an erosion rate of 0.12 nm s −1 was observed at the outer strike point [36]. At WEST a tungsten erosion rate >0.1 nm s −1 was observed at the inner and outer strike points [37]. The ratio of carbon tungsten erosion rate of 12 is also in line with measurements of the W and C erosion rates at the outer strike point of ASDEX Upgrade, where a ratio of carbon to tungsten erosion of 10-20 was observed [37].…”

Section: Test Divertor Unit (Tdu)mentioning

confidence: 96%

Erosion of tungsten marker layers in W7-X

et al. 2021

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In order to get first insight into net tungsten erosion in W7-X, tungsten (W) marker layers were exposed during the operational phase OP 1.2b at one position of the Test Divertor Unit (TDU), at 21 different positions of the inner heat shield, and at two scraper elements. The maximum tungsten erosion rate at the TDU strike line was 0.13 nm s−1 averaged over the whole campaign. The erosion was inhomogeneous on a microscopic scale, with higher erosion on ridges of the rough surface inclined towards the plasma and deposition of hydrocarbon layers in the recessed areas of the rough surface. The W erosion at the inner heat shield was below the detection limit of 3–6 × 1012 W-atoms/cm2s, and all inner heat shield tiles were covered with a thin B/C/O layer with thickness in the range 2 × 1017–1018 B + C atoms/cm2 (about 20–100 nm B + C). W-erosion of the marker layers on the scraper elements was also below the detection limit.

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Section: Test Divertor Unit (Tdu)mentioning

confidence: 96%

Erosion of tungsten marker layers in W7-X

et al. 2021

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“…The comparison of the emissivity distribution with roughness measurements indicate that the high emissivity could be attributed to different causes. In the thick deposit area (mainly B, C, O and W [36]) the roughness is in the range of the IR wavelength leading to an increase of the emissivity in addition to the compound of the deposit which are also a good emitter as B and C. The other areas with high emissivity could be due to oxide, as the iridescent color suggests, as well as first Raman measurements.…”

Section: Discussionmentioning

confidence: 80%

“…This lower emissivity is due to a decrease in the roughness in this area and a cleaning of the surface in comparison to non-exposed PFUs, which are slightly polluted by their manufacturing (see next section 3.2). Because of the 0.5 mm toroidal bevel, the emissivity is higher in the magnetically shadowed areas (left-hand part of the PFU for the OSP) up to 0.7 for the OSP PFU #22, due to impurity redeposition from neutral particles near the leading edge as observed in [36]. The poloidal extension of the low emissivity area is about 10 cm.…”

Section: Emissivity Pattern Of Sectors Q4b and Q3b Post-c4mentioning

confidence: 88%

“…After C3 and C4 experimental campaigns, W-coated PFUs with additional W marker coating have been analyzed using ion beam analyses and scanning electron microscopy techniques [36]. The net erosion and deposition patterns in the inner and outer side of the WEST lower divertor were determined.…”

Section: Comparison Of Post-mortem Measurements and Emissivity Distri...mentioning

confidence: 99%

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Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Gaspar¹,

Corre²,

Rigollet³

et al. 2022

Nucl. Fusion

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This paper summarizes the emissivity measurements performed on the plasma facing units (PFU) of the WEST lower divertor during the first phase of WEST running with a mix of actively cooled ITER-like PFUs made of bulk tungsten and inertially cooled PFUs made of graphite with a coating of tungsten. In-situ assessment of the emissivity and laboratory measurements after removing the W-coated graphite and ITER-grade PFUs from the WEST device are shown. The measurements exhibit a complex pattern with strong emissivity variation as function of space and time mainly explained with the variation of magnetic equilibrium (strike point location) as well as the plasma performances during the experimental campaigns. The exposed ITER-grade PFU exhibits sharp spatial variation of the emissivity from 0.05 to 0.85 at a monoblock scale (12mm) at the transition of the erosion (strike point location) and deposition (next to the strike point location) areas on the high field side. In the low field side, the emissivity varies from 0.12, at the strike point location, to 0.2 few cm away in the low field side direction. This emissivity range after exposure is much higher than the emissivity variation of unexposed PFU with emissivity from 0.09 to 0.15. In-situ observation performed on the W-coated graphite PFU shows a rapid evolution, typically few pulses, of the emissivity in the inner and outer strike point location. The whole spatial distribution is discussed as well as his variation due to the plasma operation from the start-up of WEST to the removal of the tungsten (W) coated graphite components.

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“…Linear plasma devices are also of interest as they deliver intermediate flux between laboratory plasma and tokamaks [24][25][26]. Post-mortem analyses are also used to obtain a before/after comparison and understand how elements migrate inside the nowadays machines [14,[27][28][29][30][31][32][33][34][35]. Ion beam analyses [36] and thermal desorption spectroscopy are key techniques that give absolute and relative content.…”

Section: Introductionmentioning

confidence: 99%

Raman microscopy to characterize plasma-wall interaction materials: from carbon era to metallic walls

Pardanaud,

Martin,

Roubin

et al. 2023

Mater. Res. Express

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Plasma-wall interaction in magnetic fusion devices is responsible for wall changes and plasma pollution with major safety issues. It is investigated both in situ and ex situ, especially by realizing large scale dedicated poWst-mortem campaigns. Selected parts of the walls are extracted and characterized by several techniques. It is important to extract hydrogen isotopes, oxygen or other element content. This is classically done by ion beam analysis and thermal desorption spectroscopy. Raman microscopy is an alternative and complementary technique. The aim of this work is to demonstrate that Raman microscopy is a very sensitive tool. Moreover, if coupled to other techniques and tested on well-controlled reference samples, Raman microscopy can be used efficiently for characterization of wall samples. Present work reviews long experience gained on carbon-based materials demonstrating how Raman microscopy can be related to structural disorder and hydrogen retention, as it is a direct probe of chemical bonds and atomic structure. In particular, we highlight the fact that Raman microscopy can be used to estimate the hydrogen content and bonds to other elements as well as how it evolves under heating. We also present state-of-the-art Raman analyses of beryllium- and tungsten-based materials, and finally, we draw some perspectives regarding boron-based deposits.

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Erosion and redeposition patterns on entire erosion marker tiles after exposure in the first operation phase of WEST

Cited by 28 publications

References 35 publications

Erosion of tungsten marker layers in W7-X

Erosion of tungsten marker layers in W7-X

Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Raman microscopy to characterize plasma-wall interaction materials: from carbon era to metallic walls

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