Integrated Modelling of Nitrogen Seeded JET ILW Discharges for H-mode and Hybrid Scenarios: Integrated Modelling of Nitrogen Seeded JET ILW Discharges for H-mode and Hybrid Scenarios

In this paper numerical simulations with COREDIV code of JET discharges with ITER-like wall are presented. We concentrate on the JET H-mode and hybrid scenarios with nitrogen seeding and all simulations have been performed with the same transport model and only the discharge input parameters like auxiliary heating P-aux, line average plasma density n(e)(lin), confinement factor H-98, nitrogen input flux Gamma(puff)(N) were changed in the calculations. The separatrix density n(c)(sep) is an input parameter in our model and has been kept equal to 0.4 divided by 0.5n(c)(lin) in the simulations, with the recycling coefficient adjusted accordingly. It has been shown that COREDIV is able to reproduce basic parameters of nitrogen seeded discharges for both H-mode and hybrid scenarios. We have achieved reasonable agreement with global plasma parameters like radiations levels, Z(eff) and tungsten concentrations and the plasma profiles, including density, temperature and radiation are in very good agreement with experimental data. The agreement of the code results with the experimental data might be even better, if the simulations are further tuned taking into account uncertainties to the sputtering model, separatrix density or SOL transport. Simulations show that the observed Z(eff) level is defined mostly by the low Z impurity content, Be and N-2 in the considered shots. It has been found that the tungsten radiation plays always very important role and can not be mitigated even by strong influx of nitrogen. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim