In order to reduce the heat load to the wall, in particular in the presence of a metallic wall, the radiated fraction is increased by means of impurity seeding. This paper aims at investigating qualitatively the balance between a degradation of the edge confinement and a potential reduction of the core turbulent transport due to the increase of effective charge, Zeff. The pedestal degradation due to the Ne seeding is taken as input. The impact of Zeff and radiative loss on the heat transport are modeled with the quasi-linear 1D fluid code RITM. The input parameters are taken from a series of Ne seeded discharges conducted in JET. Discharges with D, D + Ne and Ne only fueling are qualitatively analyzed. The model recovers the experimentally observed fact that, while the confinement is degraded from the D to the D + Ne seeded plasma, it is improved from the D + Ne to the Ne only seeded plasma.
Development of impurity seeding and radiation enhancement in the helical divertor of LHD