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Interpretation of Line-Integrated Signals from 2-D Phase Contrast Imaging on LHD

Clive MICHAEL, Kenji TANAKA, Leonid VYACHESLAVOV¹⁾, Andrei SANIN¹⁾, Kazuo KAWAHATA and S. OKAJIMA

National Institute of Fusion Science, Toki 509-0293, Japan

1)

Budker Institute for Nuclear Physics, Novisibirsk, Russia

(Received 8 December 2006 / Accepted 22 May 2007 / Published 20 November 2007)

Abstract

Two dimensional (2D) phase contrast imaging (PCI) is an excellent method to measure core and edge turbulence with good spatial resolution (Δρ ∼ 0.1). General analytical consideration is given to the signal interpretation of the line-integrated signals, with specific application to images from 2D PCI. It is shown that the Fourier components of fluctuations having any non-zero component propagating along the line of sight are not detected. The ramifications of this constraint are discussed, including consideration of the angle between the sight line and flux surface normal. In the experimental geometry, at the point where the flux surfaces are tangent to the sight line, it is shown that it may be possible to detect large poloidally extended (though with small radial wavelength) structures, such as GAMS. The spatial localization technique of this diagnostic is illustrated with experimental data.

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

Keywords

plasma, imaging, maximum entropy, correlation, turbulence, phase contrast imaging, line-integration

DOI: 10.1585/pfr.2.S1034

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This paper may be cited as follows:

Clive MICHAEL, Kenji TANAKA, Leonid VYACHESLAVOV, Andrei SANIN, Kazuo KAWAHATA and S. OKAJIMA, Plasma Fusion Res. 2, S1034 (2007).