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Correlation of the Orthogonal Basis of the Core Plasma Distribution to the Divertor Footprint Distribution in LHD

Hirohiko TANAKA, Suguru MASUZAKI^1,2), Gakushi KAWAMURA^1,2), Yuki HAYASHI^1,2), Masahiro KOBAYASHI^1,2), Yasuhiro SUZUKI³⁾, Kiyofumi MUKAI^1,2), Shin KAJITA⁴⁾ and Noriyasu OHNO

Nagoya University, Nagoya 464-8603, Japan

1)

National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan

2)

The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan

3)

Hiroshima University, Hiroshima 739-8527, Japan

4)

The University of Tokyo, Chiba 277-8561, Japan

(Received 1 December 2022 / Accepted 27 February 2023 / Published 29 March 2023)

Abstract

We have applied the multivariable analysis technique called the proper orthogonal decomposition (POD) to both the divertor particle flux distribution and the electron pressure distribution in the core region of LHD. The cross-correlation analysis indicates that 3rd, 4th, and 5th POD modes of the electron pressure distribution are highly correlated with the divertor footprint index which is a measure of where the peak position of the particle flux distribution is located on the inner divertor plate. Both the 3rd and 4th modes seem to correspond to the shift of the electron pressure peak position from the magnetic-axis radius. In contrast, 5th mode has a strong influence on the peripheral gradient of the electron pressure distribution. Their relationships with the divertor footprint could be explained by the finite β and the Pfirsch-Schlüter current effects.

Copyright (c) 2023 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

proper orthogonal decomposition, divertor footprint, toroidal divertor probe array, Thomson scattering, LHD

DOI: 10.1585/pfr.18.2402021

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