Intermittency in the Scrape-off Layer of the National Spherical Torus Experiment During H-mode Confinement
Authors: R.J. Maqueda, D.P. Stotler, S.J. Zweben, and the NSTX Team
Abstract:
A gas puff imaging diagnostic is used in the National Spherical Tokamak Experiment [M. Ono, et al., Nucl. Fusion 40, 557 (2000)] to study the edge turbulence and intermittency present during H-mode discharges. In the case of low power Ohmic H-modes the suppression of turbulence/blobs is maintained through the duration of the (short lived) H-modes. Similar quiescent edges are seen during the early stages of H-modes created with the use of neutral beam injection. Nevertheless, as time progresses following the L-H transition, turbulence and blobs reappear although at a lower level than that typically seen during L-mode confinement. It is also seen that the time-averaged SOL emission profile broadens, as the power loss across the separatrix increases. These broad profiles are characterized by a large level of fluctuations and intermittent events.
__________________________________________________
Submitted to: Journal of Nuclear Materials (May 2010)
__________________________________________________
Download PPPL-4574 (pdf 545 KB 14 pp)
__________________________________________________