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

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

doi:10.1038/s41567-021-01460-4

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

Journal Article · Mon Jan 10 00:00:00 EST 2022 · Nature Physics

DOI:https://doi.org/10.1038/s41567-021-01460-4· OSTI ID:1839161

;

; Tanaka, K.; Ashikawa, N.;

;

; Lunsford, R.;

; Ida, K.; Yoshinuma, M.; Takemura, Y.;

;

; Suzuki, C.; Nagy, A.; Bortolon, A.;

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

Sponsoring Organization:: USDOE

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

OSTI ID:: 1839161

Alternate ID(s):: OSTI ID: 1887973

Journal Information:: Nature Physics, Journal Name: Nature Physics Vol. 18 Journal Issue: 3; ISSN 1745-2473

Publisher:: Nature Publishing GroupCopyright Statement

Country of Publication:: France

Language:: English

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