Turbulent transport and turbulence in radiative I mode plasmas in TEXTOR-94

First measurements of turbulence levels and turbulence induced transport in the outer Edge of the plasma of TEXTOR-94 during radiative improved mode d ischarges show a reduction by a factor of 4-7 of the radial particle turbul ent transport. The quenching is most evident on the normalized potential fl uctuations and is strongest above 100 kHz. Non-linear gyrokinetic particle- in-cell simulations of these discharges show impurity induced suppression o f the electrostatic fluctuations associated with the ion temperature gradie nt driven mode over most of the cross-section, including the edge. Such a m echanism is proposed as the explanation for the improved confinement and tu rbulence reduction. The reduction in the edge turbulent transport levels is consistent with increased particle confinement time and the reduction of t he SOL thickness. Particle and energy fluxes to the limiter are reduced by an order of magnitude. A concomitant increase of the measured energy and pa rticle confinement times tau(E) and tau(p) versus radiated fraction suggest s a common underlying suppression mechanism.