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The interaction between waves in the ion cyclotron range of frequencies and the plasma boundary plays an important role in the success of ICRF to heat plasmas to ignition conditions. Prior to carbonisation on TEXTOR, all ICRF-heated discharges switched into strong detachment at low power levels and rapidly evolved to disruption. Changing from an all-metal to an all-carbon surrounding resulted in stationary conditions without high-Z impurity problems. Next, the use of boronisation resulted in an erosion rate lower than for carbonised walls, a significantly reduced carbon and (especially) oxygen influx, and a recycling coefficient below one, allowing density feedback control. Recently, TEXTOR has been operated with walls and limiters fully coated with silicon using plasma-assisted chemical vapour deposition from silane gases. The concentration of low-Z impurities B, C and O dropped well below the already low levels with boronisation, and Si became the dominant plasma impurity. These results indicate that siliconised wall conditioning is suitable for high power ICRH operation, despite the relatively high atomic number of silicon.

Additional information

Authors: VAN OOST G ET AL., Ecole Royale Militaire, Bruxelles (BE);EMMOTH B, MSI, Stockholm (SE);RUBEL M, MSI, Stockholm (SE);MERTENS P ET AL., Forschungszentrum Jülich GmbH (KFA) (DE)
Bibliographic Reference: Article: Proceedings of the 20th European Conference on Controlled Fusion and Plasma Physics, Vol. II (1993) pp. 671-674
Record Number: 199311159 / Last updated on: 1994-11-29
Original language: en
Available languages: en
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