Interpretation of recent power width measurements in JET MkIIGB ELMy h-modes

Results of a novel technique of measuring the deposited power profile based on thermocouples embedded in the divertor plates a-re presented and discussed. Power profiles were obtained for a series of 2.5 MA/2.4 T discharges involving a scan in the NBI heating power (4-18 MW, where PL-H similar to 5 MW) and a scan in D-2 fuelling rate ((0-3) X 10(22) s(-1)). In H-mode plasmas, a narrow feature was observed in the power profile, which scaled inversely with power entering the scrape-off-layer, lambda(q,nw) infinity p(SOL)(-0.4+/-0.1), while the base profile showed virtually no power dependence. At constant input power, the peak heat flux was strongly reduced by D2 puffing (from similar to20 to 4 MW m(-2)), with the narrow feature in the power profile effectively suppressed. Based on numerical analysis using a guiding-centre Monte-Carlo code ASCOT, coupled to a fluid-like plasma-neutral code package OSM2/EIRENE, the above results are interpreted as a consequence of inter-ELM ion orbit loss from the pedestal region.