Plasma cleaning of ITER edge Thomson scattering mock-up mirror in the EAST tokamak

Yan, Rong and Moser, Lucas and Wang, Baoguo and Peng, Jiao and Vorpahl, Christian and Leipold, Frank and Reichle, Roger and Ding, Rui and Chen, Junling and Mu, Lei and Steiner, Roland and Meyer, Ernst and Zhao, Mingzhong and Wu, Jinhua and Marot, Laurent. (2018) Plasma cleaning of ITER edge Thomson scattering mock-up mirror in the EAST tokamak. Nuclear Fusion, 58 (2). 026008.

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Official URL: http://edoc.unibas.ch/58431/

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First mirrors are the key element of all optical and laser diagnostics in ITER. Facing the plasma directly, the surface of the first mirrors could be sputtered by energetic particles or deposited with contaminants eroded from the first wall (tungsten and beryllium), which would result in the degradation of the reflectivity. The impurity deposits emphasize the necessity of the first mirror in situ cleaning for ITER. The mock-up first mirror system for ITER edge Thomson scattering diagnostics has been cleaned in EAST for the first time in a tokamak using radio frequency capacitively coupled plasma. The cleaning properties, namely the removal of contaminants and homogeneity of cleaning were investigated with molybdenum mirror insets (25 mm diameter) located at five positions over the mock-up plate (center to edge) on which 10 nm of aluminum oxide, used as beryllium proxy, were deposited. The cleaning efficiency was evaluated using energy dispersive x-ray spectroscopy, reflectivity measurements and x-ray photoelectron spectroscopy. Using argon or neon plasma without magnetic field in the laboratory and with a 1.7 T magnetic field in the EAST tokamak, the aluminum oxide films were homogeneously removed. The full recovery of the mirrors` reflectivity was attained after cleaning in EAST with the magnetic field, and the cleaning efficiency was about 40 times higher than that without the magnetic field. All these results are promising for the plasma cleaning baseline scenario of ITER.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Nanomechanik (Meyer)
UniBasel Contributors:Meyer, Ernst and Marot, Laurent
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:IOP Publishing
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:13 Jun 2023 13:14
Deposited On:15 Jan 2018 10:46

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