Status of Integrated Modelling of JET-ILW Plasmas with N2 Seeding
The N2-seeding experiments at JET were carried out in order to develop a type-I ELMy H-mode reference scenario for achieving Q = 10 in ITER compatible with the wall materials (Be main chamber, W divertor) of active operation. One objective of the experiments was to reduce the steady-state divertor-target power load by introducing a radiating extrinsic impurity (N2). An unexpected feature of N2-seeding, in high-triangularity (d) JET with an ITER-Like wall (JET-ILW) plasmas, was the observation of improved pedestal confinement at levels closer to those of JET with Carbon-Fibre-Composite Wall (JET-C). It has been suggested that the level of C and its associated radiation could have been a hidden parameter in the JET-C confinement behaviour of high-d plasmas and that this could partially be recovered by N2 seeding in JET-ILW. Detailed integrated modelling (core and SOL) of these JET-ILW discharges, with and without N2 seeding, may shed some light on the difference in plasma dynamics between high- and low-d configurations and, in particular, the improvement in confinement with high-d and N2-seeding. It is important to compare the simulations with a set of experimental parameters in the core/edge/SOL to ascertain the main physics governing these plasmas has been captured correctly. This paper reports on the present results.