Effect of ELM Mitigation on Confinement and Divertor Heat Loads on JET

In JET several techniques have demonstrated their potential for controlling the frequency and size of type I ELMs, including static external perturbation of the edge magnetic field using the Error Field Correction Coils (EFCCs) and ELM magnetic triggering by fast vertical plasma movements ('vertical kicks'). The aim of this paper is to compare the performance of the different ELM mitigation techniques in terms of both the reduction of ELM size and the impact of each control method on plasma confinement and divertor heat loads. We find that the reduction in ELM size (up to a factor of 3), independently of the method used, is always accompanied by a reduction in pedestal pressure (mainly due to a loss in density) with only a moderate (10-15%) decrease of the stored energy. Key issues have been examined such as the behaviour of the density loss and the confinement degradation with the increase in ELM frequency, the impact of mitigation on the power required for steady state operation with regular Type I ELMs and the potential of using EFCCs for ELM mitigation in helium plasmas. The results of these experiments are discussed and their implications for ITER highlighted.
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