IMPROVED PLASMA PERFORMANCE IN TEXTOR WITH SILICON COATED SURFACES

Coating of the walls of TEXTOR with silicon has led to improved tokamak plasma performance. Very low concentrations of C, B, and O are measured. Radiation from silicon is located at the plasma periphery at r/a greater-than-or-equal-to 0.75 and decreases with increasing plasma density. Density limits are enhanced by 30% as compared to boronized conditions; large density gradients and low electron temperatures at the edge (< 10 eV) are obtained. The improved confinement regimes observed earlier at low densities [tau(E) = 1.7 x ITER L 89-P (International Thermonuclear Experimental Reactor)] were extended to significantly higher densities in spite of a high radiative power fraction.