Projected profile similarity in gyrokinetic simulations of Bohm and gyro-Bohm scaled DIII-D L and H modes

Abstract

Global gyrokinetic simulations of DIII-D [M. A. Mahdavi and J. L. Luxon, in "DIII-D Tokamak Special Issue," Fusion Sci. Technol. 48, 2 (2005)] L- and H-mode dimensionally similar discharge pairs are treated in detail. The simulations confirm the Bohm scaling of the well-matched L-mode pair. The paradoxical but experimentally apparent gyro-Bohm scaling of the H-mode pair at larger relative gyroradius (rho-star) and lower transport levels is due to poor profile similarity. Simulations of projected experimental plasma profiles with perfect similarity show both the L- and H-mode pairs to have Bohm scaling. A ρ* stabilization rule for predicting the breakdown of gyro-Bohm scaling from simulations of a single discharge is presented. © 2006 American Institute of Physics.