Experiments on turbulence and transport in the edge plasma of the TEXT tokamak

The author studied the turbulence and fluctuation driven transport in the edge plasma of the TEXT tokamak using a Langmuir probe array. In this dissertation the author presents three separate experiments, each of which examines a particular aspect of the edge turbulence and transport. In the first experiment the author compares the observed fluctuation levels to the scaling predictions of several turbulence theories. The author found that the fluctuations and transport were not proportional to the density and temperature gradients. In the second experiment the author identifies low frequency modulations (≤1KHz) in the edge density, potential and temperature to be associated with heat and density pulses (sawtooth oscillations) which originate from the central region of the tokamak. Concurrent with the edge sawtooth oscillations are significant increases in the density and potential fluctuation levels. As a result of these increases, the fluctuation driven particle flux and associated heat flux are increased as much as 60 and 100% respectively during the sawtooth. The effect of electron cyclotron heating (ECH) on the edge plasma was investigated in the third experiment. Increases in edge temperature, density and potential with simultaneous increases in the density and potential fluctuations were observed during ECH. These increased fluctuation levels resulted in a significant increase (20-50%) in the fluctuation driven particle flux. Comparison of these results to an equal input power, ohmic only discharge showed similar increases in the average density, temperature and potential