Response of Plasmas to Tungsten Pellet Injection in Neutral Beam Heated Discharges in Large Helical Device

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Author(s)

    • OISHI Tetsutarou
    • National Institute for Fusion Science, National Institutes of Natural Sciences|Department of Fusion Science, SOKENDAI (Graduate University for Advanced Studies)
    • MORITA Shigeru
    • National Institute for Fusion Science, National Institutes of Natural Sciences|Department of Fusion Science, SOKENDAI (Graduate University for Advanced Studies)
    • HUANG Xianli
    • National Institute for Fusion Science, National Institutes of Natural Sciences
    • LIU Yang
    • Department of Fusion Science, SOKENDAI (Graduate University for Advanced Studies)
    • GOTO Motoshi
    • National Institute for Fusion Science, National Institutes of Natural Sciences|Department of Fusion Science, SOKENDAI (Graduate University for Advanced Studies)

Abstract

<p>Response of plasmas in Large Helical Device (LHD) to the tungsten pellet injection depends on both the total port-through power of the neutral beam injection (NBI) for heating, <i>P</i><sub>NBI</sub>, and the line-averaged electron density, <i>n</i><sub>e</sub>. The plasma can be sustained in the range of high <i>P</i><sub>NBI </sub>and low <i>n</i><sub>e </sub>while it collapses in the range of low <i>P</i><sub>NBI </sub>and high <i>n</i><sub>e</sub>. When the number of tungsten atoms enclosed in a pellet, <i>N</i><sub>W</sub>, is small, plasma can survive in low <i>P</i><sub>NBI </sub>and high <i>n</i><sub>e </sub>range. Parameter space for plasma sustainment after the pellet injection is limited to lower <i>n</i><sub>e </sub>range in more outward-shifted magnetic configuration. <i>n</i><sub>e </sub>< 4.0 × 10<sup>13 </sup>cm<sup>−3 </sup>and <i>N</i><sub>W </sub>< 1.2 × 10<sup>18</sup> for <i>R</i><sub>ax </sub>= 3.60 m, <i>n</i><sub>e </sub>< 3.0 × 10<sup>13 </sup>cm<sup>−3 </sup>and <i>N</i><sub>W </sub>< 8.7 × 10<sup>16 </sup>for <i>R</i><sub>ax </sub>= 3.75 m, and <i>n</i><sub>e </sub>< 2.0 × 10<sup>13 </sup>cm<sup>−3 </sup>and <i>N</i><sub>W </sub>< 3.1 × 10<sup>16 </sup>for <i>R</i><sub>ax </sub>= 3.90 m are appropriate parameter ranges for the plasma sustainment. This suggests that robustness against tungsten injection depends on the magnetic configurations.</p>

Journal

  • Plasma and Fusion Research

    Plasma and Fusion Research 13(0), 3402031-3402031, 2018

    The Japan Society of Plasma Science and Nuclear Fusion Research

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