ELM-induced plasma transport in the DIII-D SOL

Abstract

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are composed of fast bursts of hot, dense plasma lasting ∼25μs each that travel radially starting at the separatrix at ∼450m/s and rotate in the scrape off layer (SOL), convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but decay with radius in the SOL. The temperature decay length (∼1.2–1.5cm) is much shorter than the density decay length (∼3–8cm), which in turn decreases with increasing pedestal density. The local particle and energy flux at the wall during the bursts are 10–50% (∼1–2×1021m−2s−1) and 1–2% (∼20–30kW/m2) respectively of the LCFS average fluxes, thus particles are transported radially much more efficiently that heat.