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By using silicon as a material for wall coatings significant improvements in the tokamak performance have been obtained. These include the lowest oxygen level ever achieved in TEXTOR, an improved density limit and also an enhanced energy confinement at high central electron densities. The present paper surveys plasma properties under siliconised wall conditions with special emphasis on plasma edge physics. An outstanding property of silicon as an impurity in the plasma is its strong influence on plasma edge parameters caused by line radiation. A high radiation level of up to 70 % of the input power (1.5 MW) has been achieved, limited by the mechanisms which are responsible for the release of silicon. 0d- and 1d-models are used to simulate the highly nonlinear system. The properties are compared to plasmas in a boronised machine. Silicon and neon are compared with respect to radiation characteristics and transport to the centre. Remarkable differences in the penetration depths and central densities are reported.

Additional information

Authors: SAMM U ET AL., Forschungszentrum Jülich GmbH (KFA) (DE)
Bibliographic Reference: Article: Journal of Nuclear Materials, Vols. 220-222 (1995) pp. 25-35
Record Number: 199510891 / Last updated on: 1995-08-10
Original language: en
Available languages: en