This paper reports the impact of different confinement regimes on the 2D structure of edge turbulence. An image analysis method based on twodimensional continuous wavelet transformation is used to localize structures (blobs) in the images and to extract their geometrical characteristics (position, scale, orientation angle and aspect ratio). We study the impact of edge shearlayers on these geometrical aspects of blobs. Results show a reduction in the angular dispersion of blobs as the shear layer is established in the boundary, as well as an increase in the elongation of these structures. Similar behaviour is found in NSTX image sequences when going from L to H mode plasmas. During improved confinement regimes the number of detected blobs decreases. Some indications are found suggesting that the turbulence reduction could be scale-selective in the biasing-induced improved confinement regime of TJ-II stellarator. Perpendicular flow reversal is visualized with the cameras and the time scales for flow reversal are found to be less than 50 μs. Radially propagating structures are found in the SOL with velocities in the range ∼1000 m/s and with a poloidally asymmetric spatial distribution. © 2006 IOP Publishing Ltd Printed in the UK.
All Science Journal Classification (ASJC) codes
- Nuclear Energy and Engineering
- Condensed Matter Physics
Alonso, J. A., Zweben, S. J., Carvalho, P., De Pablos, J. L., De La Cal, E., Hidalgo, C., ... Thomsen, H. (2006). Impact of different confinement regimes on the two-dimensional structure of edge turbulence. Plasma Physics and Controlled Fusion, 48(12 B), -. https://doi.org/10.1088/0741-3335/48/12B/S44