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

Abstract

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.