Characterization of dust collected after plasma operation of all-tungsten ASDEX Upgrade

Fortuna-Zaleśna, E.; Grzonka, J.; Rasiński, M.; Balden, M.; Rohde, V.; Kurzydłowski, Krzysztof J.

doi:10.1088/0031-8949/2014/t159/014066

Cited by 14 publications

(8 citation statements)

References 14 publications

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“…It is the formation of droplets, splashes and empty spheroids or bubbles which is a concern. The empty spheroids have been found in ASDEX Upgrade [11] and in JET-ILW, i.e. two machines using W coatings.…”

Section: Discussionmentioning

confidence: 99%

“…It is crucial for the licensing process especially in connection with operation using a deuterium-tritium fuel mixture. Very thorough dust surveys have been carried out regularly at several tokamaks: TEXTOR [1][2][3][4][5][6][7][8][9], ASDEX-Upgrade [10][11][12][13], JET [14][15][16], Tore Supra [17], DIII-D [18], KSTAR [19] and other machines, as summarised by Braams [20]. JET is the most relevant machine from the reactor point of view, because of the full metal wall composed of beryllium in the main chamber and tungsten in the divertor: the ITER-Like Wall (JET-ILW) in operation since August 2011 [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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First dust study in JET with the ITER-like wall: sampling, analysis and classification

et al. 2015

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Results of the first dust survey in JET with the ITER-Like Wall (JET-ILW) are presented. The sampling was performed using adhesive stickers from the divertor tiles where the greatest material deposition was detected after the first JET-ILW campaign in 2011–2012. The emphasis was especially on sampling and analysis of metal particles (Be and W) with the aim to determine the composition, size, surface topography and internal dust structure using a large set of methods: high-resolution scanning and transmission electron microscopy, focused ion beam, electron diffraction and also wavelength and energy dispersive x-ray spectroscopy. The most important was the identification of beryllium dust both in the form of flakes and droplets with dimensions in the micrometer range. Tungsten, molybdenum, inconel constituents were identified along with many impurity species. The particles are categorised and the origin of the various constituents discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First dust study in JET with the ITER-like wall: sampling, analysis and classification

et al. 2015

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“…In ASDEX Upgrade (AUG), starting after campaign 1999, the complete transition from a carbon to a full tungsten first wall [43,44] was monitored. Dust was collected in maintenance periods and analysed [25,[45][46][47][48][49][50][51] in order to observe the evolution of the dust composition after operation phases with different first wall configurations. Based on these investigations, a classification of sampled particles into dust and debris was proposed [47].…”

Section: Introductionmentioning

confidence: 99%

Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade

et al. 2014

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Abstract.The dust collection and analysis strategy in ASDEX Upgrade (AUG) is described. During five consecutive operation campaigns (2007)(2008)(2009)(2010)(2011), Si collectors were installed, which were supported by filtered vacuum sampling and collection with adhesive tapes in 2009. The outer and inner morphology (e.g. shape) and elemental composition of the collected particles were analysed by scanning electron microscopy. The majority of the ~50000 analysed particles on the Si collectors of campaign 2009 contain tungsten -the plasma-facing material in AUG -and show basically two different types of outer appearance: spheroids and irregularly shaped particles. By far most of the W-dominated spheroids consist of a solid W core, i.e., solidified W droplets. A part of these particles is coated with low Z material; a process which seems to happen presumably in the far scrape off layer plasma. In addition, some conglomerates of B, C, and W appear as spherical particles after their contact with plasma. By far most of the particles classified as B-, C-, and W-dominated irregularly shaped particles consist of the same conglomerate with varying fraction of embedded W in the B-C matrix and some porosity, which can exceed 50%. The fragile structures of many conglomerates confirm the absence of intensive plasma contact. Both the ablation and mobilization of conglomerate material and the production of W droplets are proposed to be triggered by arcing. The size distribution of each dust particle class is best described by a lognormal distribution allowing an extrapolation of the dust volume and surface area. The maximum in this distribution is observed above the resolution limit of 0.28 µm only for the W-dominated spheroids, at around 1 µm. The amount of W-containing dust is extrapolated to be less than 300 mg on the horizontal areas of AUG.

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“…For these reasons, tungsten (W) has been the choice of the ITER committee to be the divertor material [1][2][3]. Despite its promising low erosion properties, W material facing edge plasma was identified as a source of dust production mainly during transient events and associated power excursions [4][5][6]. It is well known that dusts created by volume chemistry of sputtered atoms in conventional plasmas exhibit size distributions ranging from tens to hundreds nm.…”

Section: Introductionmentioning

confidence: 99%

Demonstration of multi-generational growth of tungsten nanoparticles in hydrogen plasma usingin situlaser extinction method

Ouaras¹,

Lombardi²,

Hassouni³

2018

J. Phys. D: Appl. Phys.

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For the first time, we demonstrate that tungsten (W) nanoparticles (NPs) are created when a tungsten target is exposed to low-pressure, high density hydrogen plasma. The plasma was generated using a novel dual plasma system combining a microwave discharge and a pulsed direct-current (DC) discharge. The tungsten surface originates in the multi-generational formation of a significant population of 30–70 nm diameter particles when the W cathode is biased at ~ −1 kV and submitted to ~1020 m2 s−1 H+// ions flux. The evidenced NPs formation should be taking into account as one of the consequence of the plasma surface interaction outcomes, especially for fusion applications.

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Characterization of dust collected after plasma operation of all-tungsten ASDEX Upgrade

Cited by 14 publications

References 14 publications

First dust study in JET with the ITER-like wall: sampling, analysis and classification

First dust study in JET with the ITER-like wall: sampling, analysis and classification

Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade

Demonstration of multi-generational growth of tungsten nanoparticles in hydrogen plasma usingin situlaser extinction method

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