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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. Carlstrom^4)
 
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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