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P: Fachverband Plasmaphysik
P 21: Plasma- Wand- Wechselwirkung
P 21.3: Vortrag
Donnerstag, 28. Februar 2013, 17:15–17:30, HS 3
Removal of deuterated carbon codeposits by ion cyclotron wall conditioning plasmas in TEXTOR — •Sören Möller1, Arkadi Kreter1, Tom Wauters2, Gennady Sergienko1, and Ulrich Samm1 — 1Institute for Energy- and Climate Research - Plasma Physics, Forschungszentrum Jülich GmbH, Association EURATOM-FZJ, Partner in Trilateral Euregio Cluster, Jülich, Germany — 2LPP-ERM/KMS, Association Euratom-Belgian State, 1000 Brussels, Belgium
Experiments to quantify the removal rates of deuterated carbon codeposits by ion cyclotron resonance frequency (ICRF) plasmas in hydrogen, deuterium and oxygen were conducted in the tokamak TEXTOR. By variation of the gas pressure, magnetic fields and ICRF power the plasmas were optimized to obtain the highest removal rates. The removal rates were assessed by exposing pre-characterized samples. A special holder allowed for exposing samples at several radial positions and with parallel and perpendicular orientations with respect to the toroidal magnetic field. Pre- and post-exposure characterization of the layers was performed by ellipsometry and nuclear reaction analysis.
The highest removal was obtained with deuterium plasma, resulting in complete layer removal, corresponding to a rate of at least 84nm/min. Oxygen plasma reached 38nm/min. The ion fluxes, as measured by Langmuir probes, in the deuterium plasma were about 60 times larger compared to the oxygen plasma, leading to a higher removal rate. The resulting yields of carbon erosion fit into the existing database.