SOLPS-ITER drift modelling of JET Ne and N-seeded H-modes

Abstract

• SOLPS-ITER predictive modeling with drifts of Ne and N seeded JET high power H-mode. • Ne as efficient as N at separatrix Z eff < 1.5 decreasing target heat load by factor ~3. • Better divertor retention of N then Ne in deep detachment. • Beneficial impact of machine size in improving impurity retention. A numerical study is presented, using the SOLPS-ITER plasma boundary code with full drifts and currents activated, of impurity seeded JET discharges in support of high power H-mode experimental campaigns designed to compare two ITER candidate seeding species, nitrogen (N) and neon (Ne). Fluid-kinetic edge plasma simulations are first performed at lower levels of power into the scrape-off layer (SOL) and benchmarked against existing JET experimental data. Calculations are then performed for higher levels of SOL power to examine the impact of this key parameter on the efficiency of both radiators. From the code point of view, for the chosen JET parameters, Ne can be as efficient a divertor radiator as N at the same level of upstream separatrix Z eff < 1.5 for moderate seeding, decreasing the peak power at outer target by factor ~ 3. Full detachment (state with the temperature below 5 eV along all the target) at the outer target can be obtained with both impurities at higher seeding, but in the case of Ne this leads to a higher Z eff and significant radiation in the main SOL/pedestal. The indications from this JET code modelling, in comparison with previous similar simulations for ITER and ASDEX Upgrade with drifts turned on, are that there is a beneficial impact of machine size in improving impurity retention, substantiating the claim that both N and Ne will perform well as seed impurities for divertor power dissipation in ITER.