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(THP1/16) X Transport and its Effect on H-mode and Edge Pedestal in Tokamaks

C. S. Chang¹⁾, D. Darrow³⁾, S. H. Ku⁵⁾, H. Weitzner²⁾, R. White³⁾, Z. Lin³⁾, W. Lee³⁾, T. N. Carlstrom⁴⁾, J. S. deGrassie^4)
 
1) New York University, New York, U.S.A. and KAIST, Korea
²⁾ New York University, New York, U.S.A.
³⁾ PPPL, Princeton, U.S.A.
⁴⁾ General Atomics, San Diego, U.S.A.
⁵⁾ Department of Physics, KAIST, Korea

Abstract.  A new classical non-ambipolar transport mechanism has been identified which can be a dominant source of strong Er and edge pedestal layer formation immediately inside the separatrix in a diverted tokamak. Due to vanishingly small poloidal B-field and grad-B drift toward x-point, plasma ions with small v_| in the X-region do not have confined single particle orbits. This leads to a non-ambipolar convective transport in the X-region (X-transport), either collisional or collisionless, inducing a strong negative Er-shear layer. The X-transport can provide basic understanding of many of the experimental observations.

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