Observation of inward turbulent particle transport in edge plasma region of CHS heliotron/torsatron

K. Toi*, K. Ohkuni, M. G. Shats, R. Akiyama, M. Goto, M. Isobe, G. Matsunaga, K. Matsuoka, T. Minami, S. Morita, S. Nishimura, I. Nomura, S. Okamura, M. Osakabe, A. Shimizu, C. Suzuki, S. Takagi, C. Takahashi, M. Takechi, K. TanakaY. Yoshimura

*Corresponding author for this work

    Research output: Contribution to journalConference articlepeer-review

    5 Citations (Scopus)

    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.

    Original languageEnglish
    Article number323
    Pages (from-to)A237-A243
    JournalPlasma Physics and Controlled Fusion
    Volume44
    Issue number5 A
    DOIs
    Publication statusPublished - May 2002
    Event8th IAEA Technical Committee Meeting on H-Mode Physics and Transport Barriers - Toki, Japan
    Duration: 5 Sept 20017 Sept 2001

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