NIFS-856

FULL TEXT (PDF, 296 KB)

Author(s):

S. Ohdachi et al.

Title:

Two-Dimensional Structure of MHD Instabilities and their Non-Linear Evolution in the Large Helical Device

Date of publication:

Oct. 2006

Key words:

21 IAEA Fusion Energy Conference , EX/P8-15

Abstract:

It is a key goal on the way to fusion to better understand the role that magneto hydrodynamic (MHD) instabilities do play in plasma confinement in helical systems. We experimentally study the evolution of pressure driven modes in the Large Helical Device (LHD) using images measured by a fast, tangentially-viewing soft X-ray camera. Sawtooth-like MHD activity occurs in high-density plasmas when the pressure gradient in the core region exceeds a certain limit. It is found that the magnetic surfaces are strongly deformed just before the sawtooth crash. The magnetic reconnection due to this deformation may cause a rapid energy flow from the core to the edge.

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