Plasma-Wall Heat Loads in ITER-Like Advanced Tokamak Scenarios on JET
Advanced Tokamak (AT) scenarios have been developed with the aim of steady-state operation. They operate at relatively low densities (central line average density: ne,av 4¥1019 m-3 on JET) and high additional power (20MW Padd 30MW on JET), both of which necessary to ensure a large fraction of non inductive current. This leads to hot edge plasmas (20 Te 30eV at the targets on JET) and hence low recycling condition with partial divertor detachment difficult, if not impossible to achieve. The power handling capability of the Plasma-Facing Components (PFC) during AT scenarios is a key issue regarding the next planned JET enhancements: Padd increased to 45MW with duration up to 20s, and the ITER-like wall project: beryllium PFCs for the main chamber and a tungsten divertor. For the first time on JET an attempt has been made to characterise the edge plasma of AT scenarios in an ITER-like configuration. New AT scenarios have been developed to investigate their compatibility with plasma-wall interactions. In particular impurity injection techniques have been developed for two reasons: the reduction of the continuous heat load on the divertor target by increasing the radiated fraction, which is discussed in the present paper, and the ELM mitigation in order to reduce their penetration in the core plasma and avoid the destruction of the Internal Transport Barrier (ITB), which is discussed in. Impurity injection techniques have also been studied on JET in hybrid scenarios with type-III ELMs.