Heat transport at the boundary of ASDEX Upgrade

The flow of heat in the scrape-off layer (SOL) region of ASDEX Upgrade is investigated and compared with simple modelling. Parallel heat transport is found to be consistent with electron heat conduction based on Spitzer-Harm conductivity. Cross-field heat transport is characterized using radial e-folding distances for power, temperature and plasma pressure, which are all found to vary weakly over a wide range of discharge conditions. Type I ELMs, also characterized, introduce a discreteness to the power flow into the SOL and carry approximately half of the power exhaust from the discharge. The divertor plates are effectively screened from the ELM energy, even in low-radiation discharges, suggesting enhanced radiation rates during ELMs. (Author)