Observation of a reduced-turbulence regime with boron powder injection in a stellarator

Nespoli, Federico ; Masuzaki, Suguru; Tanaka, Kenji; Ashikawa, Naoko; Shoji, Mamoru; Gilson, Erik ; Oishi, Tetsutarou; Ida, Katsumi; Yoshinuma, Mikirou; Takemura, Yuki; Kinoshita, Toshiki; Motojima, Gen; Kenmochi, Naoki; Kawamura, Gakushi; Suzuki, Chihiro; Nagy, Alex ; Bortolon, Alessandro ; Pablant, Novimir ; Mollén, Albert ; Tamura, Naoki; Gates, David ; Morisaki, Tomohiro
Issue date: 2022
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Nespoli, Federico, Masuzaki, Suguru, Tanaka, Kenji, Ashikawa, Naoko, Shoji, Mamoru, Gilson, Erik, Oishi, Tetsutarou, Ida, Katsumi, Yoshinuma, Mikirou, Takemura, Yuki, Kinoshita, Toshiki, Motojima, Gen, Kenmochi, Naoki, Kawamura, Gakushi, Suzuki, Chihiro, Nagy, Alex, Bortolon, Alessandro, Pablant, Novimir, Mollén, Albert, Tamura, Naoki, Gates, David, & Morisaki, Tomohiro. (2022). Observation of a reduced-turbulence regime with boron powder injection in a stellarator [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.34770/3f28-m424
@electronic{nespoli_federico_2022,
  author      = {Nespoli, Federico and
                Masuzaki, Suguru and
                Tanaka, Kenji and
                Ashikawa, Naoko and
                Shoji, Mamoru and
                Gilson, Erik and
                Oishi, Tetsutarou and
                Ida, Katsumi and
                Yoshinuma, Mikirou and
                Takemura, Yuki and
                Kinoshita, Toshiki and
                Motojima, Gen and
                Kenmochi, Naoki and
                Kawamura, Gakushi and
                Suzuki, Chihiro and
                Nagy, Alex and
                Bortolon, Alessandro and
                Pablant, Novimir and
                Mollén, Albert and
                Tamura, Naoki and
                Gates, David and
                Morisaki, Tomohiro},
  title       = {{Observation of a reduced-turbulence regi
                me with boron powder injection in a stel
                larator}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2022,
  url         = {https://doi.org/10.34770/3f28-m424}
}
Description:

In state-of-the-art stellarators, turbulence is a major cause of the degradation of plasma confinement. To maximize confinement, which eventually determines the amount of nuclear fusion reactions, turbulent transport needs to be reduced. Here we report the observation of a confinement regime in a stellarator plasma that is characterized by increased confinement and reduced turbulent fluctuations. The transition to this regime is driven by the injection of submillimetric boron powder grains into the plasma. With the line-averaged electron density being kept constant, we observe a substantial increase of stored energy and electron and ion temperatures. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range between 100 and 200 kHz are excited. We have observed this regime for different heating schemes, namely with both electron and ion cyclotron resonant radio frequencies and neutral beams, for both directions of the magnetic field and both hydrogen and deuterium plasmas.

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