Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST

Santanu Banerjee, H. Zushi, N. Nishino, Kazuaki Hanada, Hiroshi Idei, K. Nakamura, Makoto Hasegawa, akihide fujisawa, Yoshihiko Nagashima, K. Mishra, S. Tashima, Takumi Onchi, A. Kuzmin, K. Matsuoka

Research output: Contribution to journalArticle

Abstract

Intensity fluctuations are investigated using the fast camera imaging technique in the slab annular plasma as a function of magnetic shear and connection length in the spherical tokamak QUEST. Note that here QUEST is operated as a simple magnetized torus with a tight aspect ratio. Slab annular plasmas feature open magnetic field lines and can mimic the tokamak edge-scrape off layer (SOL)-like plasma attributes reasonably well. Three magnetic shear regimes are realized using three poloidal magnetic field (PF) coil pairs. A whole range of connection lengths (∼∞ ≥ L c ≥ 5.5 m) is scanned by varying the PF strength for a given toroidal field for each magnetic shear regime. For the first time a systematic study of the effect of magnetic shear and field line pitch together on edge-SOL-like plasma fluctuations is being reported. Slab plasmas with intermediate magnetic shear are observed to be more susceptible to generate distinct blobs when L c is reduced by increasing the PF strength. A distinct coherent mode appears only at the lowest magnetic shear slab featuring a deep potential well. Such mode is not apparent at other magnetic shear cases even at the same L c. Finally, with a combination of PF coil pairs, both the features of intermediate and low magnetic shear slabs are shown to be realizable simultaneously. Significantly stronger blobs are observed with such combination of PF mirror ratios in the presence of a coherent mode. This study may provide better insight into the effect of magnetic configuration in the tokamak edge and SOL turbulence and can help in searching for better tools to control cross-field convective intermittent transport in tokamaks.

Original languageEnglish
Article number085014
JournalPlasma Physics and Controlled Fusion
Volume60
Issue number8
DOIs
Publication statusPublished - Jun 28 2018

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Turbulence
turbulence
Magnetic fields
shear
Plasmas
configurations
slabs
magnetic fields
field coils
plasma layers
field strength
plasma slabs
Aspect ratio
Mirrors
Cameras
imaging techniques
Imaging techniques
aspect ratio
cameras
mirrors

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this

Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST. / Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, Kazuaki; Idei, Hiroshi; Nakamura, K.; Hasegawa, Makoto; fujisawa, akihide; Nagashima, Yoshihiko; Mishra, K.; Tashima, S.; Onchi, Takumi; Kuzmin, A.; Matsuoka, K.

In: Plasma Physics and Controlled Fusion, Vol. 60, No. 8, 085014, 28.06.2018.

Research output: Contribution to journalArticle

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AU - Idei, Hiroshi

AU - Nakamura, K.

AU - Hasegawa, Makoto

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AU - Nagashima, Yoshihiko

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AU - Tashima, S.

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