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Abstract

Boronisation of the TCA vacuum vessel was performed at ambient temperature. The paper presents a detailed surface analysis of the coating and a description of the tokamak performance after boronisation. The coatings showed a film composition close to the feed gas composition, although a high oxygen content was found. Apart from the dominating carbidic B-C bonds, at least two non-equivalent carbon bonding sites were found. Boronisation gave an immediate and long-term improvement of many plasma parameters in TCA with a strong reduction of both low- and high-Z impurities in the plasma. In particular, oxygen was reduced by a factor of over 20, despite a high level oxygen contamination in the coating. The gas retention in the film was temporarily reduced by glow discharge cleaning. With these techniques, nearly isotopically pure discharges were obtained. Boronisation is shown to be a very efficient wall conditioning procedure in TCA.

Additional information

Authors: HOLLENSTEIN C ET AL., Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH);KÜNZLI H J, Universität Basel, Institut für Physik, Basel (CH);OELHAFEN P, Universität Basel, Institut für Physik, Basel (CH);ZEHRINGER R, Universität Basel, Institut für Physik, Basel (CH);HAUERT R, Swiss Laboratories for Materials Testing and Research, Dübendorf (CH);MOSER E M, Swiss Laboratories for Materials Testing and Research, Dübendorf (CH);KUNZLI H J, Universitat Basel, Institut fur Physik, Basel (CH)
Bibliographic Reference: Paper presented: 9th International Conference on Plasma Surface Interactions in Controlled Fusion Devices, Bournemouth (GB), May 21-25, 1990
Availability: Available from (1) as Paper EN 35448 ORA
Record Number: 199110796 / Last updated on: 1994-12-02
Category: PUBLICATION
Original language: en
Available languages: en
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