Interpretive modeling of simple-as-possible-plasma discharges on DIII-D using the OEDGE code

Abstract

Recently a number of major, unanticipated effects have been reported in tokamak edge research raising the question of whether we understand the controlling physics of the edge. This report is on the first part – here focused on the outer divertor – of a systematic study of the simplest possible edge plasma – no ELMs, no detachment, etc. – for a set of 10 repeat, highly diagnosed, single-null, divertor discharges in DIII-D. For almost the entire, extensive data set so far evaluated, the matches of experiment and model are so close as to imply that the controlling processes at the outer divertor for these simple plasma conditions have probably been correctly identified and quantitatively characterized in the model. The principal anomaly flagged so far relates to measurements of T e near the target, potentially pointing to a deficiency in our understanding of sheath physics in the tokamak environment.