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(EX/P3-07) The Effect of Drifts on the DIII-D Boundary Plasma

G.D. Porter¹⁾, T.D. Rognlien¹⁾, M.E. Rensink¹⁾, N.S. Wolf¹⁾, T.W. Petrie²⁾, W.P. West²⁾, P.C. Stangeby³⁾, DIII-D Team^2)
 
1) Lawrence Livermore National Laboratory, Livermore, USA
²⁾ General Atomics, La Jolla, CA, USA
³⁾ Univcersity of Toronto, Toronto, Canada

Abstract.  We examine detailed experimental measurement of in/out asymmetries in single-null divertor experiments and in/out and up/down asymmetries in double-null experiments in DIII-D to determine their origin. The 2-D fluid code UEDGE including the physics of ExB and $\nabla$B drifts as well as a full treatment of intrinsic carbon impurities is used to aid understanding the experimental results. The in/out asymmetries observed in L-mode single-null experiments are consistent with the effect of flow from the outer divertor to the inner via ExB drifts arising from the radial electric field along the separatrix. This enhances the density on the high field side, increasing line emission in both carbon and hydrogen species, consistent with experiment. The up/down asymmetries seen in magnetically imbalanced H-mode double null plasmas are consistent with the effect of a combination of $\nabla$B and ExB drifts. Divertor heating remains strongest on the lower divertor for balanced double-null with $\nabla$B drift downward. Balanced power distribution requires a dominant X-point on the top, as seen experimentally. *Work supported by U.S. DOE Contracts W-7405-ENG-48 (LLNL) and DE-AC03-99ER54463 (GA).

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