EFDA-JET-CP(06)05/18

ELM Transport in the JET Scrape-Off Layer

This contribution summarises a number of aspects of the experimental and modelling programme at JET aimed at improving the characterisation and understanding of ELM transport in the Scrape-Off Layer (SOL). Divertor target energy deposition asymmetries favouring the inner target for the ion B¥B drift directed towards the X-point are observed with Infra-Red (IR) thermography. Particle-in-Cell kinetic calculations of the parallel ELM heat transport have been made for a range of ELM energies, showing the detailed time response of target sheath heat transmission factors and indicating that electrons deposit ~30% of the ELM energy. A transient model of ELM filament energy evolution has been developed at JET and is able to reproduce a number of experimental observations, including the high ion energies observed in the far SOL using an electrostatic Retarding Field electrostatic Analyser (RFA) and estimates of ELM heat fluxes deposited on main chamber limiters. During the ELM, the RFA and a second, SOL turbulence probe, clearly show the presence of coherent spikes on the hot ion flux, the plasma flux and the electron temperature. Filamentary structures have also been seen for the first time on JET in the power deposition on main wall limiters and upper dump plate surfaces using a new wide angle IR camera system. The probe signals are interpreted as the arrival of interspaced, toroidally rotating plasma filaments, with successive filaments carrying less energy. They are also consistent with the ELM disturbance entering the SOL on the outboard side and launching a sound wave disturbance along field lines.
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EFDC060518 570.23 Kb