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(TH/5-1) Nonlinear Simulation Studies of Tokamaks and ST's

W. Park¹⁾, J. Breslau¹⁾, J. Chen¹⁾, G.Y. Fu¹⁾, S.C. Jardin¹⁾, S. Klasky¹⁾, J. Menard¹⁾, A. Pletzer¹⁾, B.C. Stratton¹⁾, D. Stutman¹⁾, H.R. Strauss²⁾, L.E. Sugiyama^3)
 
1) Princeton University Plasma Physics Laboratory, Princeton, NJ, USA
²⁾ New York University, New York, New York, USA
³⁾ Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

Abstract.  The multilevel physics, parallel processing plasma simulation code, M3D has been used to study tokamaks and ST's. MHD simulation of NSTX IRE's shows crashes similar to sawtooth crashes. To explain a long saturated m=1 phase often seen in experiment, effects of strong sheared toroidal flow, and non-MHD effects are being studied. Sheared toroidal rotation can cause the density peak shifts outward relative to the magnetic axis by 0.15 of the minor radius. Two-fluid effects does not change this substantially, but the energetic particle anisotropy can further modify the density profile. These results are generally consistent with experimental measurements. The linear growth rates of global internal modes are typically reduced by several-folds due to sheared rotation. 3D nonlinear evolution of m=1 mode shows that saturation depends on various parameters including the momentum source rate. MHD studies of recent tokamak experiments with central current hole indicate that the current clamping is due to sawtooth like crashes, but with n=0. Gyrokinetic hot particle/MHD hybrid studies of NSTX show the effects of fluid compression on a fast ion-driven n=1 mode.

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