Title : Understanding the Saturation and Suppression of Turbulence in Magnetized Plasmas
Speaker : Prof.Kenneth W. Gentle
From : University of Texas at Austin,APS fellow
Date : 2010.12.05
Abstract: Inhomogeneous plasmas are always found to be in a turbulent state with transport rates much higher than that of collisional fluids. Understanding the processes that control the level of turbulence and rate of transport has proven to be a difficult task. One generic candidate is flow shear, driven either internally by zonal flows or externally by momentum input, but experimental evidence is largely circumstantial. Observations in a large basic physics device with a simple geometry, the cylindrical slab, which has dimensionless parameters similar to those of the edge of a tokamak, show saturated turbulence with no production of zonal flows. Most important, the turbulence level can be greatly reduced by application of bias, which alters the flow patterns. However, there is no correlation between the local turbulence level and local flow shear. Other processes must control the turbulence levels.