TRANSPORT AND FLUCTUATIONS IN THE INTERIOR OF DIII-D PLASMAS

A series of H-mode discharges from DIII-D has been analysed to find a possible correlation between turbulent fluctuations and thermal transport in the core of the DIII-D tokamak. The one-fluid thermal diffusivity as given by the transport code ONETWO is observed to peak in the region 0.7 less-than-or-equal-to rho less-than-or-equal-to 0.9 where the bulk of the electrostatic fluctuations is located in the H-mode. Also the time evolution of the thermal diffusivity and the fluctuations in this region are very similar: both transport and fluctuations are suppressed after the L-H transition, but the suppression is not abrupt (as it is at the edge) but rather gradual, extending over tens of milliseconds. It is thus concluded that transport and microturbulence in the interior of the DIII-D plasmas appear to be strongly correlated.