M. Schmidtmayr, J. Hughes, F. Ryter, E. Wolfrum, N. Cao, A. Creely, N. Howard, A. Hubbard, Y. Lin, M. Reinke, J. Rice, E. Tolman, S. Wukitch, Y. Ma, . ASDEX Upgrade Team, Alcator C-Mod Team:

"Investigation of the critical edge ion heat flux for L-H transitions in Alcator C-Mod and its dependence on BT";

Nuclear Fusion,58(2018), 0560031 - 0560039.

This paper presents investigations on the role of the edge ion heat flux for transitions from L-mode to H-mode in Alcator C-Mod. Previous results from the ASDEX Upgrade tokamak indicated that a critical value of edge ion heat flux per particle is needed for the transition. Analysis of C-Mod data confirms this result. The edge ion heat flux is indeed found to increase linearly with density at given magnetic field and plasma current. Furthermore, the Alcator C-Mod data indicate that the edge ion heat flux at the L-H transition also increases with magnetic field. Combining the data from Alcator C-Mod and ASDEX Upgrade yields a general expression for the edge ion heat flux at the L-H transition. These results are discussed from the point of view of the possible physics mechanism of the L-H transition. They are also compared to the L-H power threshold scaling and an extrapolation for ITER is given.

L-H transition, Alcator C-Mod, power threshold

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