Changes in edge and scrape-off layer plasma behavior due to variation in magnetic balance in DIII-D

Changes in the divertor magnetic balance in DIII-D H-mode plasmas affects core, edge, and divertor plasma behavior. Both the pedestal density n(ePED) and plasma stored energy W-T were sensitive to changes in magnetic balance near the double-null (DN) configuration, e.g., both decreased 20-30% when the DN shifted to a slightly unbalanced DN, where the B x delB. drift direction. pointed away from the main X-point. Recycling at each of the four divertor targets was sensitive to changes in magnetic balance and the B x delB drift direction. The poloidal distribution of the recycling in DN is in qualitative agreement with the predictions of UEDGE modeling with particle drifts included. The particle flux at the inner divertor target is shown to be much more sensitive to magnetic balance than the particle flux at the outer divertor target near the DN shape. These results suggest possible advantages and drawbacks for balanced DN operation. (C) 2003 Elsevier Science B.V. All rights reserved.