Three-dimensional dynamics of turbulence in the edge of fusion plasmas

For the first time, the three-dimensional nature of drift waves has been verified experimentally inside the confinement region of a toroidal plasma. It was shown that the propagation in the direction parallel to the magnetic field is affected by Alfvén dynamics. The cross phase between density and potential fluctuations is small, which is consistent with the drift-wave model. These results strongly confirm previous investigations, which have demonstrated the importance of drift-wave turbulence in TJ-K and therefore also in fusion edge plasmas. The measurements show that turbulent fluctuations on the low-field side are responsible for a major fraction of turbulent transport. This asymmetry of the turbulent transport could be related to magnetic field curvature effects, which becomes important on the low-field side.