First measurements of turbulence levels and turbulence inducedtransport in the outer edge of the plasma of TEXTOR-94 duringradiative improved mode discharges show a reduction bya factor of 4-7 of the radial particle turbulent transport.The quenching is most evident on the normalized potential fluctuationsand is strongest above 100 kHz. Non-linear gyrokinetic particle-in-cellsimulations of these discharges show impurity induced suppressionof the electrostatic fluctuations associated with the iontemperature gradient driven mode over most of the cross-section, including the edge. Such a mechanism is proposed asthe explanation for the improved confinement and turbulencereduction. The reduction in the edge turbulent transport levelsis consistent with increased particle confinement time and the reductionof the SOL thickness. Particle and energy fluxes to the limiter arereduced by an order of magnitude. A concomitant increase of themeasured energy and particle confinement times τE and τp versusradiated fraction suggests a common underlying suppression mechanism.
Edge turbulence transport during ELM suppression with n = 4 resonant magnetic perturbation on EAST