Active Control of Type-I Edge-Localized Modes withn=1Perturbation Fields in the JET Tokamak

Abstract

Type-I edge-localized modes (ELMs) have been mitigated at the JET tokamak using a static external $n=1$ perturbation field generated by four error field correction coils located far from the plasma. During the application of the $n=1$ field the ELM frequency increased by a factor of 4 and the amplitude of the ${\mathrm{D}}_{\alpha }$ signal decreased. The energy loss per ELM normalized to the total stored energy, $\Delta W/W$, dropped to values below 2%. Transport analyses shows no or only a moderate (up to 20%) degradation of energy confinement time during the ELM mitigation phase.