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(EXP2/11) Comparison of L-H Transition Measurements with Physics Models

   
T. N. Carlstrom , K. H. Burrell , R. J. Groebner , F. L. Hinton , M. A. Mahdavi , G. M. Staebler , A. W. Leonard , T. H. Osborne , and D. M. Thomas 
General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
 
B. A. Carreras , R. Maingi , P. K. Mioduszewski , L. W. Owen 
Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
 
R. Lehmer , R. A. Moyer 
University of California, San Diego, California, USA
 
G. D. Porter 
Lawrence Livermore National Laboratory, Livermore, California, USA
 
J. G. Watkins 
Sandia National Laboratories, Albuquerque, New Mexico, USA

Abstract
Sawteeth and neutrals  are found to have a significant influence on the H-mode  power threshold scaling. The ion $\rm\nabla B$ drift direction has only a small effect on the edge plasma conditions measured near the plasma midplane but a large effect on the divertor plasma. Since the power threshold changes dramatically with the direction of the ion $\rm\nabla B$ drift, this implies that phenomena in the divertor region  are critical for the L-H transition . Local conditions at the plasma edge are consistent with several theories of the L-H transition that use edge gradients in their formulation of a critical threshold parameter. However, scatter in the database is too large to distinguish between conditions that lead to an L-H transition and those that remain in L-mode .

 

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