Interplay between ballooning and peeling modes in simulations of the time evolution of edge localized modes

Interplay between ballooning and peeling modes in simulations of the time evolution of edge localized modes

Interplay between ballooning and peeling modes in simulations of the time evolution of edge localized modes 150 150 Mathew

Interplay between ballooning and peeling modes in simulations of the time evolution of edge localized modes

The time evolution of edge localized modes ( ELMs ) in the Joint European Torus tokamak [ P. H. Rebut and et al. , Nucl. Fusion 25 , 1011 ( 1985 )] is investigated using the JETTO predictive modeling code [ M. Erba and et al. , Plasma Phys. Controlled Fusion 39 , 261 ( 1997 )] . It is found that both pressure-driven ballooning and current-driven peeling modes can play a role in triggering the ELM crashes. In the simulations carried out, each large ELM consists of a sequence of quasicontinuous small ELM crashes. Each sequence of ELM crashes is separated from the next sequence by a relatively longer ELM-free period. The initial crash in each ELM sequence can be triggered either by a pressure-driven ballooning mode or by a current-driven peeling mode, while the subsequent crashes within that sequence are triggered by current-driven peeling modes, which are made more unstable by the reduction in the pressure gradient resulting from the initial crash. The HELENA and MISHKA ideal magnetohydrodynamic stability codes [ A. B. Mikhailovskii and et al. , Plasma Phys. Rep. 23 , 713 ( 1997 )] are used to validate the stability criteria used in the JETTO simulations. This stability analysis includes infinite- n ideal ballooning, finite- n ballooning, and low- n kink/peeling modes.

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15/12/2004