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Abstract

Steady-state and transient power deposition profiles have been measured in the JET MIIGB divertor using improved diagnostic techniques involving the use of fast infrared (IR), thermocouples and Langmuir probe arrays. In unfuelled type I ELMy H-modes a very narrow power profile is observed at the outer target, which we associate with the ion channel. Systematic parameter scans have been carried out and our analysis shows that the average power width scaling is consistent with a classical dependence of perpendicular transport in the SOL. Using the fast IR capability, factors such as rise time, broadening, variability and in/out asymmetry have been studied and lead to the conclusion that, within the extrapolation errors, type I ELMs in ITER are likely to have energies comparable to the ablation limits of the divertor material. JET disruptions are very different from type I ELMs in that only a small fraction of the thermal energy reaches the divertor and what does arrive is distributed uniformly over the divertor area. This is very different from the current ITER assumption that puts most of the energy from the thermal quench onto the divertor strike points.