Düsseldorf 2007 – scientific programme

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P: Fachverband Plasmaphysik

P 11: Diagnostische Methoden

P 11.2: Talk

Wednesday, March 21, 2007, 11:45–12:00, 6C

A remote ellipsometer for TEXTOR — •Timo Dittmar¹, Achim von Keudell¹, and Arkadi Kreter² — ¹Ruhr-Universität Bochum — ²Forschungszentrum Jülich

Deposition and erosion of plasma faced surfaces within fusion reactors are a key issue for the life time estimation of the first wall of present and future fusion experiments. At present an in-situ estimate of both, the erosion rates and changes in composition and texture of the deposited layers is not possible. This gap could be closed with ellipsometry. It provides mono layer film thickness resolution and allows the precise and sensitive determination of the optical properties of thin films with high accuracy. This makes ellipsometry suitable to study processes at the plasma-wall interface in real time. Nevertheless, conventional ellipsometric instruments are not compatible with the Tokamak environment due to the Faraday-effect in the retarding elements and problems with optical access to the divertor region. The limitations of conventional Ellipsometry can be overcome with the construction of an in-situ reverse ellipsometry probe head using a four diode stokesmeter. In this contribution we present the results during the testing and calibration of our miniature ellipsometric probe head on an ICP reactor and the first results from campaigns at TEXTOR.