PPPL-4000 is available in pdf format (2.5 MB).

Microturbulent Drift Mode Stability before Internal Transport Barrier Formation in the Alcator C-Mod Radio Frequency Heated H-mode

Authors: M.H. Redi, W. Dorland, C.L. Fiore, P.T. Bonoli, M.J. Greenwald, J.E. Rice, J.A. Baumgaertel, T.S. Hahm, G.W. Hammett, K. Hill, D.C. McCune, D.R. Mikkelsen, and G. Rewoldt

Date of PPPL Report: August 2004

H-mode experiments on Alcator C-Mod [I.H. Hutchinson, et al., Phys. Plasma 1 (1994) 1511] which exhibit an internal transport barrier (ITB), have been examined with gyrokinetic simulations, near the ITB onset time. Linear simulations support the picture of ion and electron temperature gradient (ITG, ETG) microturbulence driving high χi and χe, respectively, and that stable ITG correlates with reduced particle transport and improved ion thermal confinement on C-Mod. In the barrier region ITG is weakly unstable, with a critical temperature gradient higher than expected from standard models. Nonlinear calculations and the role of ExB shear suppression of turbulence outside the plasma core are discussed in light of recent profile measurements for the toroidal velocity. The gyrokinetic model benchmarks successfully against experiment in the plasma core.