Integrated Core+Edge+SOL+MHD Modelling of ELM Mitigation at JET
In JET C and W/Be wall experiments, the use of ELM pacing at high ELM frequency as a tool to mitigate the ELM impact on plasma facing components and for impurity control has been successfully investigated. To improve the understanding of ELM mitigation mechanisms at JET in view of ITER and to examine dependencies of the ELM trigger efficiency on available actuators, modelling schemes are required, combining the evolution of the plasma core, edge and SOL and the analysis of MHD stability in an integrated way. The JET transport suite of codes JINTRAC has been used in fully integrated modeto study and assess physical processes that appear to be relevant in case of ELMs triggered (a) by application of magnetic field perturbations that cause a sudden displacement of the plasma ("kicks") and (b) by injection of pellets. Whereas induced edge current perturbations were found to be relevant to destabilise the plasma edge in case (a), local and plasmoid-driven pressure perturbations are held responsible for the appearance of an ELM in case (b). In the context of previous integrated simulation studies of ELM pacing / mitigation by kicks and pellets at JET, recent advances are reported on the following subjects: ­ ELM mitigated regimes are analysed with JINTRAC in fully integrated mode in a refined way using a new tool for the evaluation of the MHD stability at runtime with HELENA+MISHKA. ­ The effect of kicks at low vs. high kick amplitude / gas fuelling rate in JET C and W/Be wall discharges on MHD stability is analysed and compared against experimental findings with JINTRAC+CREATE-NL.