A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

Nespoli, F.; Tanaka, K.; Masuzaki, S.; Ashikawa, N.; Shoji, M.; Gilson, E. P.; Lunsford, R.; Oishi, T.; Ida, K.; Yoshinuma, M.; Takemura, Y.; Kinoshita, T.; Motojima, G.; Osakabe, M.; Kenmochi, N.; Kawamura, G.; Suzuki, C.; Nagy, A.; Bortolon, A.; Pablant, N. A.; Mollen, A.; Tamura, N.; Gates, D. A.; Morisaki, T.

doi:10.1088/1741-4326/acd465

Title: A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

Journal Article · 19 May 2023 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/acd465 · OSTI ID:1974493

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Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
National Institute for Fusion Science (Japan); Kyushu Univ., Fukuoka (Japan)
National Institute for Fusion Science (Japan); Graduate University for Advanced Studies (SOKENDAI) (Japan)
National Institute for Fusion Science (Japan)
Kyushu Univ., Fukuoka (Japan)

Recently an improved confinement regime, characterized by reduced turbulent fluctuations has been observed in the Large Helical Device upon the injection of boron powder into the plasma (Nespoli et al 2022 Nat. Phys.18 350–56). In this article, we report in more detail the experimental observations of increased plasma temperature and the decrease of turbulent fluctuations across the plasma cross section, on an extended database. In particular, we compare powders of different materials (B, C, BN), finding similar temperature improvement and turbulence response for the three cases. Modeling of the powder penetration into the plasma and of neoclassical electric field and fluxes support the interpretation of the experimental results. Additionally, we report evidence of the temperature improvement increasing with powder injection rates and decreasing for both increasing density and heating power. Though, plasma turbulence response varies depending on the initial conditions of the plasma, making it difficult to draw an inclusive description of the phenomenon.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC02-09CH11466; AC02- 09CH11466

OSTI ID:: 1974493

Alternate ID(s):: OSTI ID: 1973300; OSTI ID: 1986322

Journal Information:: Nuclear Fusion, Vol. 63, Issue 7; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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