Observation of Inward Turbulent Particle Transport in Edge Plasma Region of CHS Heliotron/Torsatron
Date
2002
Authors
Toi, K
Ohkuni, K
Shats, Michael
Akiyama, R
Goto, M
Isobe, M
Matsunaga, G
Matsuoka, K
Minami, T
Morita, S
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Physics Publishing
Abstract
Reversal of turbulent particle flux near the plasma edge of CHS heliotron/torsatron was observed on various discharge conditions, i.e. during tangential neutral beam injection, electron cyclotron heating at the far edge, and the sawtooth crash. For all cases, the reversal is realized at a narrow particular layer near the plasma edge, when plasma parameters go into low collisionality. The reversal is caused by the change in the cross phase between density (ne) and poloidal electric field (Eθ) fluctuations. The turbulent flux is always inward when the radial electric field shear (E′r) exceeds a certain threshold of ∼1 × 106V m-2. In the sawtoothing plasmas, the arrival of a heat pulse due to the sawtooth crash enhances both ne and Eθ fluctuations but changes the cross phase to π in low-frequency range. As a result, a large inward flux is generated by the sawtooth crash. The particle flux reversal in these cases did not lead to obvious confinement improvement.
Description
Keywords
Keywords: Carrier concentration; Electric fields; Electron cyclotron resonance; Electrostatics; Tokamak devices; Electron cyclotron heating; Heliotron; Neutral beam injection; Poloidal electric field fluctuations; Radial electric field shear; Sawtooth crash; Torsat
Citation
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Source
Plasma Physics and Controlled Fusion
Type
Journal article