Interpretation of Radiative Divertor Studies with Impurity Seeding in Type-I ELMy H-mode Plasmas in JET-ILW using EDGE2D-EIRENE

Nitrogen seeded JET-ILW H-mode plasmas have been investigated with EDGE2D-EIRENE. The simulations reproduce the experimentally observed factor of 10 reduction in the outer target power deposition when the normalized divertor radiation, Praddiv/PSOL, increases from the unseeded levels of 15% up to the 50% levels required for detachment. At these radiation levels, nitrogen is predicted dominate the total radiation with a contribution of 85%, consistent with previous measurements in JET-C. Due to low radiative potential of nitrogen in the electron temperatures above 100eV, more than 80% of the radiation is predicted to occur in the scrape-off layer, making nitrogen a suitable divertor radiator for typical JET divertor conditions with Te around 30eV. The simulations reproduce the experimentally observed particle flux reduction at the low-field side target without the need for strong recombination. This is due to low power levels entering the deuterium ionization front, inaccessible without strong impurity radiation.
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