EFDA-JET-PR(01)40
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 2.5MA/2.4T discharges involving a scan in the NBI heating power (4-18MW, where PL-H ~5 MW) and a scan in D2 fuelling rate (0-3¥1022 s-1). In H-mode plasmas, a narrow feature was observed in the power profile, which scaled inversely with power entering the SOL, lq,nw µ PSOL-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 ~20 to 4 MW/m2), 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.