Plasma and Fusion Research

Volume 20, 1202037 (2025)

Rapid Communications

Identification of Ballooning-Type Pressure Driven Instability by Tomographic Reconstruction
Kentaro TAKEDA1), Yasuhiro SUZUKI1), Yuki TAKEMURA2,3), Kenji TANAKA2,5), Toshiki KINOSHITA4), Hikona SAKAI5)
1)
Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
2)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
3)
The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu 509-5292, Japan
4)
Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
5)
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
(Received 10 March 2025 / Accepted 27 May 2025 / Published 25 July 2025)

Abstract

This paper deals with the experimental identification of the mode structure for the CDC by the tomographic reconstruction. Theoretically, it was predicted the CDC is triggered by the high-n ballooning mode. In the experiment, the localized density fluctuations at the outboard side are observed at the onset, and this is evidence that the ballooning-like instability triggers the CDC. Still, it was not well confirmed because the mode structure is not experimentally understood yet. To understand the mode structure, a new tomographic reconstruction is developed by coupling the Fourier-Bessel series expansion method and sparse modeling with L1 regularization. Using this, the ballooning-like mode structure of the density fluctuations is successfully reconstructed at the precursor.

Keywords

CDC, ballooning mode, tomography

DOI: 10.1585/pfr.20.1202037

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