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(EX/P5-03) Nonlinear Simulations of Drift-Wave Turbulence in Alcator C-Mod

D.R. Mikkelsen1), W. Dorland2), D.W. Ross3), M. Greenwald4), S. Wolfe4), P. Bonoli4), C. Fiore4), A. Hubbard4), J. Irby4), E. Marmar4), D. Mossessian4), J. Rice4), G. Taylor1), J. Terry4)
1) Princeton Plasma Physics Laboratory, Princeton, USA
2) University of Maryland, College Park, MD, USA
3) Fusion Research Center, University of Texas, Austin, TX, USA
4) Plasma Science and Fusion Center, MIT, Cambridge, MA, USA

Abstract.  We present turbulence simulations of transport that are compatible with measurements in the core of typical H-mode plasmas in Alcator C-Mod. Our two-species nonlinear gyrokinetic simulations of turbulent transport due to long wavelength electrostatic drift-type instabilities employ a flux-tube domain based on a realistic non-circular magnetic geometry. These simulations with GS2 differ from previous work by including both trapped electron effects and finite collisionality. The results can reconcile theory and experiment by means of a nonlinear upshift of the effective critical gradient. This upshift is not present in simulations with collisionality lowered to a level typical of other tokamaks. An upshift is recovered at low collisionality if kinetic electron effects are ignored by using an adiabatic electron treatment - a simplification made in previous reports of such an upshift - but the transport in the region above the effective critical gradient is less stiff than with a more complete kinetic treatment at the C-Mod collisionality. We conclude that it is important to include both collisions and non-adiabatic electron effects in simulations of turbulent transport in tokamaks.

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IAEA 2003