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 are 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 <iopmath latex="$P_{{\rm L}\scriptsize-{\rm H}}\sim 5$">P_L-H~5</iopmath> MW) and a scan in D₂ fuelling rate <iopmath latex="$((0-3)\times 10^{22}$">((0-3)×10²²</iopmath> s<iopmath latex="$^{ - 1}$">^-1</iopmath>). In H-mode plasmas, a narrow feature was observed in the power profile, which scaled inversely with power entering the scrape-off-layer, <iopmath latex="$\lambda _{q, {\rm nw} } \propto P_{\rm SOL}^{ - 0.4\pm 0.1}$">λ_q,nw&propto;P_SOL^-0.4±0.1</iopmath>, while the base profile showed virtually no power dependence. At constant input power, the peak heat flux was strongly reduced by D₂ puffing (from <iopmath latex="$\sim $">~</iopmath>20 to 4 MW m<iopmath latex="$^{-2}$">^-2</iopmath>), 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.