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

Nespoli, Federico; Tanaka, Kenji; Masuzaki, Suguru; Ashikawa, Naoko; Shoji, Mamoru; Gilson, Erik; Lunsford, Robert; Oishi, Tetsutarou; Ida, Katsumi; Yoshinuma, Mikirou; Takemura, Yuki; Kinoshita, Toshiki; Motojima, Gen; Osakabe, Masaki; Kenmochi, Naoki; Kawamura, Gakushi; Suzuki, Chihiro; Nagy, Alex; Bortolon, Alessandro; Pablant, Novimir; Mollen, Albert; Tamura, Naoki; Gates, David; Morisaki, Tomohiro
Issue date: 19 May 2023
Cite as:
Nespoli, Federico, Tanaka, Kenji, Masuzaki, Suguru, Ashikawa, Naoko, Shoji, Mamoru, Gilson, Erik, Lunsford, Robert, Oishi, Tetsutarou, Ida, Katsumi, Yoshinuma, Mikirou, Takemura, Yuki, Kinoshita, Toshiki, Motojima, Gen, Osakabe, Masaki, Kenmochi, Naoki, Kawamura, Gakushi, Suzuki, Chihiro, Nagy, Alex, Bortolon, Alessandro, Pablant, Novimir, Mollen, Albert, Tamura, Naoki, Gates, David, & Morisaki, Tomohiro. (2023). A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders [Data set]. Princeton Plasma Physics Laboratory, Princeton University.
@electronic{nespoli_federico_2023,
  author      = {Nespoli, Federico and
                Tanaka, Kenji and
                Masuzaki, Suguru and
                Ashikawa, Naoko and
                Shoji, Mamoru and
                Gilson, Erik and
                Lunsford, Robert and
                Oishi, Tetsutarou and
                Ida, Katsumi and
                Yoshinuma, Mikirou and
                Takemura, Yuki and
                Kinoshita, Toshiki and
                Motojima, Gen and
                Osakabe, Masaki and
                Kenmochi, Naoki and
                Kawamura, Gakushi and
                Suzuki, Chihiro and
                Nagy, Alex and
                Bortolon, Alessandro and
                Pablant, Novimir and
                Mollen, Albert and
                Tamura, Naoki and
                Gates, David and
                Morisaki, Tomohiro},
  title       = {{A reduced-turbulence regime in the Large
                 Helical Device upon injection of low-Z
                materials powders}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2023
}
Abstract:

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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