Wave launching as a diagnostic tool to investigate plasma turbulence (abstract)

An experimental scheme to extend the investigation of plasma turbulence has been implemented. It involves driving waves into the plasma to modify the statistical properties of the fluctuations; the dynamical balance of the turbulence is perturbed via the injection of waves at selected spectral regions. New analysis techniques based on conditional sampling and high order correlation are developed for studying the wave launching and the wave-wave coupling processes. Experimental results from TEXT-U tokamak show that the launched waves interact with the intrinsic fluctuations both linearly and nonlinearly. The attainment of driven nonlinearity is necessary for this diagnostic scheme to work. It is also the key to an active modification and control of edge turbulence in tokamaks.