Edge localized modes control by stochastic magnetic fields

M. Bécoulet, G.T.A. Huysmans, P. Thomas, P. Ghendrih, E. Nardon, A. Grosman, X. Garbet, W. Zwingman, R. Moyer, T. Evans, M. Schaffer, A. Leonard

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)

Abstract

This paper describes a new approach for modelling the pedestal energy transport in the presence of a small radial magnetic perturbation. The cases of a ballooning instability leading to Type I edge localized modes (ELMs) and a magnetic perturbation generated by external coils are treated. The model for Type I ELMs is based on the linear ideal MHD code MISHKA coupled with the non-linear energy transport code TELM in a realistic tokamak geometry. The main mechanism of the increased transport through the external transport barrier in this model of ELMs is due to the appearance of a radial velocity and a radial magnetic field perturbation due to the MHD mode. Both lead to additional transport perpendicular to the magnetic surface and hence to a relaxation of the pressure profile in the unstable zone. The typical Type I ELM time-cycle was reproduced numerically including the destabilization of the ballooning modes leading to the fast (250 μ s) collapse of the pedestal pressure followed by the edge pressure profile re-building on a diffusive time scale. A possible mechanism for the control of Type I ELMs using a stochastic plasma boundary created by external coils is modelled in this paper using data on ELM suppression by I-coils from the DIII-D experiment. In the stochastic layer the transverse transport is effectively increased by diffusion of the magnetic field lines. The modelling results demonstrate the possibility of decreasing the edge pressure gradient to a value that is just below the ideal ballooning limit, leading to a high confinement regime without Type I ELMs.
Original languageEnglish
Pages (from-to)1284-1292
JournalNuclear Fusion
Volume45
Issue number11
DOIs
Publication statusPublished - 1 Nov 2005
Externally publishedYes

Fingerprint

Dive into the research topics of 'Edge localized modes control by stochastic magnetic fields'. Together they form a unique fingerprint.

Cite this