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(TH4/4) Turbulence Simulations of X Point Physics on the L-H Transitions

X. Q. Xu1), R. H. Cohen1), W. M. Nevins1), G. D. Porter1), M. E. Rensink1), T. D. Rognlien1), J. R. Myra2), D. A. D'Ippolito2), R. A. Moyer3), P. B. Snyder4), T. N. Carlstrom4)
 
1) Lawrence Livermore National Lab., Livermore, CA 94551, USA
2) Lodestar Research Corporation, Boulder, CO, 80301, USA
3) University of California, San Diego, La Jolla, CA 92093, USA
4) General Atomics, San Diego, CA 92186 USA

Abstract.  We show that the resistive X-point mode is the dominant mode in boundary plasmas in X-point divertor geometry. The poloidal fluctuation phase velocity from the simulation results of the resistive X-point turbulence shows experimentally measured structure across separatrix in many fusion devices. The fluctuation phase velocity is larger than E×B velocity both in L and H mode phases. We also demonstrate that there is a strong poloidal asymmetry of particle flux in the proximity of the separatrix. Turbulence suppression in the L-H transition results when sources of energy and particles drive sufficient gradients as in the experiments.

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IAEA 2001