Formation and Propagation of Pre-ELM Footprint Structures at JET

Abstract

Recent resonant magnetic perturbation experiments at JET have shown the formation of pre-ELM footprint structures. Theses structures appear as a divertor heat load pattern a few milliseconds before and continuing until the ELM crash. The excitation of the pre-ELM structures is accompanied by a drop of the edge electron temperature. A dynamic nature of these structures was found and studied for different edge safety factors. A thermoelectric current model shows that current filaments in the plasma edge can cause a strong topology change, leading to the creation and propagation of such structures. Comparisons between the experimental findings and the modelling approach, are discussed