DOE OSTI · 3007207
Impurity Powder Injection Experiments in the Large Helical Device
Abstract
The Impurity Powder Dropper (IPD) is a device capable of injecting controlled amounts of sub-millimetre powder into the plasma under the action of gravity. In 2019 the IPD was first installed on the Large Helical Device (LHD) in Japan, with the aim of improving the plasma performances through real time boronization and assessing the compatibility of this technique with steady state operation. Extensive series of experiments have been performed using the IPD, focused on the improvement of the plasma performance via low-Z powder injection and the understanding of the underlying physical phenomena. In this article, we review the experiments that took place in the period 2019-2024. The main results include the demonstration of the improvement of the wall conditions (reduction of intrinsic impurity content, wall recycling) both on a shot-to-shot basis and in real time. Furthermore, a reduced-turbulence improved confinement regime has been observed coincident with powder injection, resulting in an increase of the plasma temperature of the order of 25%, with enhancements that can reach up to 50% for ion temperature.
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Nespoli, F. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:000000017644751X), Masuzaki, S. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Tanaka, K. [National Institute for Fusion Science (NIFS), Gifu (Japan); Kyushu Univ., Fukuoka (Japan)], Shoji, M. [National Institute for Fusion Science (NIFS), Gifu (Japan)], Lunsford, R. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000335886801), Ashikawa, N. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan); Kyoto Fusioneering Ltd., Tokyo (Japan)], Gilson, E. P. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000168209132), Tamura, N. [Max Planck Institute for Plasma Physics, Greifswald (Germany)], Medina-Roque, D. [Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain). Laboratorio Nacional de Fusion], Kawate, T. [National Institutes for Quantum Science and Technology (QST), Naka (Japan)], Oishi, T. [Tohoku Univ., Sendai (Japan)], Ida, K. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Yoshinuma, M. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Takemura, Y. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Kinoshita, T. [Kyushu Univ., Fukuoka (Japan)], Motojima, G. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Osakabe, M. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Kenmochi, N. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Kawamura, G. [National Institutes for Quantum Science and Technology (QST), Aomori (Japan)], Singh, T. [Lehigh Univ., Bethlehem, PA (United States)], Takahashi, H. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Ogawa, K. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Suzuki, C. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)], Nagy, A. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000282012528), Bortolon, A. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000200940209), Pablant, N. A. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000166178459), Mollen, A. [KTH Royal Inst. of Technology, Stockholm (Sweden)] (ORCID:0000000292577864), Gates, D. A. [Thea Energy, Inc., Kearny, NJ (United States)] (ORCID:0000000156793124), Morisaki, T. [National Institute for Fusion Science (NIFS), Gifu (Japan); Graduate University for Advanced Studies (SOKENDAI), Gifu (Japan)]. 2025-11-27. Impurity Powder Injection Experiments in the Large Helical Device. https://doi.org/10.1007/s10894-025-00535-x
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