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Analyses of Visible Images of the Plasma Periphery Observed with Tangentially Viewing CCD Cameras in the Large Helical Device

M. SHOJI, T. WATANABE, S. MASUZAKI, H. YAMADA, A. KOMORI and LHD Experimental Groups

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

(Received 4 December 2006 / Accepted 18 March 2007 / Published 20 November 2007)

Abstract

Magnetic field produced by helical and poloidal coils in LHD forms a complicated structure of the magnetic field lines in the plasma periphery (ergodic layer and divertor legs), which can change the radial position of the magnetic axis, the shape and size of magnetic surfaces and the location of the strike points, etc. CCD cameras have observed complicated structure of the visible emission depending on the magnetic configurations. The dependence of the images of visible emission on three magnetic parameters which specify magnetic configurations (the position of the magnetic axis, coil pitch parameter, quadruple magnetic components) is investigated by tracing magnetic field lines. The images of the three-dimensional plots of the magnetic field lines quite agree with the observations in various magnetic configurations. Safe operational range of the three magnetic parameters from the viewpoint of minimizing the direct heat load onto the vacuum vessel is found by calculating the distributions of strike points.

Copyright (c) 2007 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

visible image, plasma periphery, CCD camera, Large Helical Device, magnetic field line, strike point, magnetic axis, coil pitch parameter, quadrupole magnetic component

DOI: 10.1585/pfr.2.S1046

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References

• [1] M. Shoji et al., J. Nucl. Mater. 337-339, 186 (2005).

This paper may be cited as follows:

M. SHOJI, T. WATANABE, S. MASUZAKI, H. YAMADA, A. KOMORI and LHD Experimental Groups, Plasma Fusion Res. 2, S1046 (2007).