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Pedestal: Difference between revisions
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When transiting from the L-mode to the H-mode, the appearance of the pedestal often leaves the profile gradients in the core region intact (due to [[Profile consistency|profile consistency]]) whereas the edge gradients increase sharply. Thus, it appears as if the core profiles are merely shifted upward (as if put upon a pedestal), hence the terminology. | When transiting from the L-mode to the H-mode, the appearance of the pedestal often leaves the profile gradients in the core region intact (due to [[Profile consistency|profile consistency]]) whereas the edge gradients increase sharply. Thus, it appears as if the core profiles are merely shifted upward (as if put upon a pedestal), hence the terminology. | ||
Physically, the edge region is complex as it is bounded by the [[Separatrix|separatrix]] | Physically, the edge region is complex as it is bounded by the [[Separatrix|separatrix]] signalling the transition from the confined plasma with closed field lines to the scrape-off layer (SOL) with open field lines; transport fluxes are large there; and the interaction with the wall (atomic and molecular physics) is important. | ||
As a consequence, the understanding of this region, and therefore of the pedestal, is still imperfect. | As a consequence, the understanding of this region, and therefore of the pedestal, is still imperfect. | ||
Many attempts have been made to derive [[Scaling law|scaling laws]] of phenomenological pedestal parameters (such as its width and height), with limited success. | Many attempts have been made to derive [[Scaling law|scaling laws]] of phenomenological pedestal parameters (such as its width and height), with limited success. | ||