Effect of magnetic geometry on ELM heat flux profiles

In this paper, we explore how precisely the magnetic up/down symmetry must be controlled to insure sharing of edge localized mode (ELM) heat flux between upper and lower divertors in a double-null tokamak. We show for DIII-D, using infrared thermography, that the spatial distribution of Type-I ELM energy is less strongly affected by variations in magnetic geometry than the time-averaged peak heat flux in attached discharges. The degree of control necessary to share ELM heat flux deposition equally between divertors was less stringent than the control needed to balance the time-averaged heat flux. ELM energy is transported more than four times further into the scrape-off layer (SOL) than the time-averaged heat flux.