Reduction of Divertor Heat Load in JET ELMy H-modes using Impurity Seeding Techniques
The investigation of methods for a reduction of divertor heat loads in order to increase the lifetime of divertor tiles in future fusion reactors is the main objective of this paper. Special emphasis is given to the reduction of transient heat loads due to Edge Localised Modes (ELMs). Two methods are compared: Argon seeded type-I ELMy H-modes and Nitrogen seeded type-III ELMy H-modes. In both scenarios the impurity seeding leads to a reduction of the pedestal energy and hence a reduction of the energy released by the ELM. This consequentially reduces the power load to the divertor targets. At high radiative power fractions in type-III ELMy H-modes part of that released ELM energy (25 kJ) is dissipated by radiation in the Scrape Off Layer (SOL). Modelling of the ELM mitigation supports the experimental findings. Both scenarios might be compatible with an integrated ITER scenario, with respect to acceptable divertor lifetime and acceptable confinement.