Characterisation of deposited hydrocarbon layers below the divertor and in the 
pumping ducts of ASDEX Upgrade

Mayer, M.; Rohde, V.; von Keudell, A.; ASDEX Upgrade Team,

doi:10.1016/S0022-3115(02)01407-1

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Characterisation of deposited hydrocarbon layers below the divertor and in the pumping ducts of ASDEX Upgrade

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Mayer, M.
Material Research (MF), Max Planck Institute for Plasma Physics, Max Planck Society;

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Rohde, V.
Experimental Plasma Physics 1 (E1), Max Planck Institute for Plasma Physics, Max Planck Society;

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von Keudell, A.
Centre for Interdisciplinary Plasma Science (CIPS), Max Planck Institute for Plasma Physics, Max Planck Society;
Surface Science (OP), Max Planck Institute for Plasma Physics, Max Planck Society;

ASDEX Upgrade Team,
Max Planck Institute for Plasma Physics, Max Planck Society;

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Citation

Mayer, M., Rohde, V., von Keudell, A., & ASDEX Upgrade Team (2003). Characterisation of deposited hydrocarbon layers below the divertor and in the pumping ducts of ASDEX Upgrade. Journal of Nuclear Materials, 313-316, 429-433. doi:10.1016/S0022-3115(02)01407-1.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0027-2F5D-F

Abstract

The growth of codeposited layers has been studied with long term samples below the divertor IIb and in a pump duct of ASDEX Upgrade from March to August 2001. The composition of redeposited layers and their optical properties were analyzed with ion beam techniques and ellipsometry. The deposition in the sub-divertor area showed a complicated deposition pattern with a maximum deposition of about 1.3 μm. All deposits form soft hydrocarbon layers which consist ainly of deuterium and carbon with D/C from 0.7 to 1.4. Only a small deposition was observed in the pump duct, with a maximum of about 2.5×1015 D-atoms/cm² at the duct entrance. The observed deposition pattern in the duct is compared with simulation calculations assuming neutral hydrocarbon radicals as precursors for film deposition. The deposition pattern can be explained by two different radical species with surface loss probabilities β<10-3 and 0.1≤β≤0.9. The most likely species are CD3, C2D5 and C2D3 radicals.