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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. Terry^4)
 
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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