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(EX/C2-3) Correlation of H-mode Density Barrier Width and Neutral Penetration Length

R.J. Groebner1), M.A. Mahdavi1), A.W. Leonard1), T.H. Osborne1), N.S. Wolf2), G.D. Porter2), P.C. Stangeby3), N.H. Brooks1), R.J. Colchin4), W.W. Heidbrink5), T.C. Luce1), G.R. McKee6), L.W. Owen4), G. Wang7), D.G. Whyte8)*)
1) General Atomics, San Diego, USA
2) Lawrence Livermore National Laboratory, Livermore, California, USA
3) University of Toronto, Toronto, Canada
4) Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
5) University of California, Irvine, California, USA
6) University of Wisconsin, Madison, Madison, Wisconsin, USA
7) University of California, Los Angeles, California, USA
8) University of California, San Diego, La Jolla, California, USA
*Present address: University of Wisconsin, Madison, Madison, Wisconsin, USA

Abstract.  Pedestal studies in DIII-D find a good correlation between the width of the H-mode particle barrier width ne and the neutral penetration length. These results are obtained by comparing experimental ne profiles to the predictions of an analytic model for the density profile, obtained from a solution of the particle continuity equations for electrons and deuterium atoms. Initial bench-marking shows that the model is consistent with the fluid neutrals model of the UEDGE code. In its range of validity (edge temperature between 0.02 - 0.3 keV), the model quantitatively predicts the observed values of width(ne), the observed decrease of width(ne) as the pedestal density ne, ped increases, the observed increase of the gradient of ne with the square of ne, ped, and the observation that L-mode and H-mode profiles with the same ne, ped have very similar widths. In the model, width(ne) depends on the fuelling source and on the plasma transport. Thus, these results provide evidence that the width of the particle barrier depends on both plasma physics and atomic physics. *Work supported by U.S. DOE under Contracts DE-AC03-99ER55463, W-7405-ENG-48, and DE-AC05-00OR22725.

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IAEA 2003