Dependence of the L–H transition on separatrix-wall gaps on TdeV

Steady-state H-modes have been obtained on TdeV both with ECRH and Lower Hybrid heating. Power thresholds are comparable with those predicted by the ITER scaling laws. A very pronounced threshold in edge density is observed, below which no L-H transitions occur. H-L transitions occur at significantly lower values of edge density. When the edge density exceeds the threshold, H-modes are produced both with an outboard limiter and with the divertor baffle within one density scrape-off layer of the separatrix. In the former case, confinement was degraded, in the latter, it was improved. (C) 1999 Elsevier Science B.V. All rights reserved.