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 betw een upper and lower diverters in a double-null tokamak. We show for DIII-D, using infrared thermography, that the spatial distribution of Type-I ELM e nergy 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 Aux deposition equally between diverters was l ess stringent than the control needed to balance the time-averaged heat flu x. ELM energy is transported more than four times further into the scrape-o ff layer (SOL) than the time-averaged heat flux. (C) 2001 Elsevier Science B.V. All rights reserved.