Scrape-off layer heat transport and divertor power deposition of pellet-induced edge localized modes

Abstract

Results on key aspects of scrape-off layer (SOL) heat transport and divertor power load associated with pellet-induced edge localized modes (ELMs) in comparison with spontaneous ELMs are presented. We focus on the 3D structure of the SOL heat transport by revealing the footprints of power load on the divertor target. Additionally, the time scales of ELM loss and consecutive energy transport in the SOL toward the divertor target of pellet-induced ELMs are discussed.By employing a toroidal magnetic field (BT) scan we achieve evidence that a toroidally asymmetric divertor power deposition structure is extending to positions exceptionally far off the strike line and exceeding toroidally localized the power flux density at the strike line. Field line tracing is used to predict correctly for the full BT scan the position of the divertor power footprint of an ELM filament through the pellet injection trajectory. Consistently the divertor heat flux modeled with the non-linear MHD-code JOREK features in addition to the toroidally symmetric component peaking at the strike line a spiral-like structure joining this symmetric component from higher radii. For the investigated JET discharges we conclude that the divertor heat loads due to pellet-induced ELM consist of two components. First, the toroidally symmetric peak heat load at the strike line is comparable to the one of spontaneous ELMs. Secondly, the toroidal asymmetric component is found to be higher by ∼30% at a toroidal position defined by the SOL field line pitch.