Heat-flow change induced by active radiation loss in open magnetic flux of steady-state spherical tokamak

2016 Fiscal Year Annual Research Report

• Project/Area Number: 15K17800
• Research Institution: Kyushu University
• Principal Investigator: 恩地 拓己 九州大学, 応用力学研究所, 学術研究員 (00727216)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: プラズマ / 熱流束 / 放射損失 / 球状トカマク / 長時間放電

Outline of Annual Research Achievements

磁場閉じ込めプラズマ核融合炉におけるプラズマ対向材料の崩壊を防ぐ方法として，能動的放射損失による熱流速低減が重要であり，その実験的検証のための研究を行った．球状トカマク装置QUESTにおいて，スクレイプオフ層（SOL）及び真空容器壁位置でのプラズマ計測を行うための複合静電プローブを利用して電子温度，電子密度，熱流束の計測を実施した．実験では特に約2時間の長時間トカマク放電における計測で，放電終盤の電子密度上昇・電子温度低下を観測した．この電子密度上昇は真空容器内の水素分子圧力上昇と共に発生しており，プラズマ電流維持を困難に導いた結果，トカマク配位の崩壊につながる．このように本研究で開発した複合プローブによる計測を中性粒子（ガス分圧）の観測と併用することで，長時間トカマク放電維持に対する重要な知見を得ることが出来た．今後の課題として，長時間トカマク放電時の線放射量を指標にして，スクレイプオフ層や壁への電子温度・密度・熱流束を系統的に調べることが必要である．また局所的ガス入射システムの改造を行った．短時間のバルブ開閉を可能とするパルスバルブ用のガス圧を20気圧以上に調整するための配管を行い，ラバルノズルを用いたスクレイプオフ層への局所ガス入射が可能になった．次の課題として高電流トカマクへの局所ガス入射実験を実施して能動的に放射損失を増加させ，スクレイプオフ層及び壁における熱流束の変化を調べる予定である．

Research Products

• [Journal Article] Spatial distribution of atomic and ion hydrogen flux and its effect on hydrogen recycling in long duration confined and non-confined plasmas (2017)
  • Author(s): A Kuzmin, H Zushi, I Takagi, SK Sharma, M Kobayashi, Y Hirooka, T Onchi, K Hanada, N Yoshida, K Nakamura, A Fujisawa, H Idei, Y Nagashima, M Hasegawa, T Mutoh, K Mishra, H Ohwada
  • Journal Title: Nuclear Materials and Energy Volume: - Pages: -
  • DOI: http://doi.org/10.1016/j.nme.2017.03.027
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Permutation entropy and statistical complexity in characterising low-aspect-ratio reversed-field pinch plasma (2017)
  • Author(s): T Onchi, A Fujisawa, A Sanpei, H Himura, S Masamune
  • Journal Title: Physica Scripta Volume: 92 Pages: 055601
  • DOI: https://doi.org/10.1088/1402-4896/aa6689
  • Peer Reviewed
• [Journal Article] Hydrogen flux measurements with permeation probes in spherical tokamak QUEST (2016)
  • Author(s): A Kuzmin, H Zushi, I Takagi, SK Sharma, Y Hirooka, M Kobayashi, M Sakamoto, K Hanada, T Onchi, Y Oyama, N Youshida, K Nakamura, A Fujisawa, H Idei, Y Nagashima, M Hasegawa, K Mishra
  • Journal Title: Vacuum Volume: 129 Pages: 178-182
  • DOI: http://doi.org/10.1016/j.vacuum.2016.04.025
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Observation of an edge coherent mode and poloidal flow in the electron cyclotron wave induced high βp plasma in QUEST (2016)
  • Author(s): Santanu Banerjee, H Zushi, N Nishino, K Mishra, Y Mahira, S Tashima, A Ejiri, T Yamaguchi, T Onchi, Y Nagashima, K Hanada, K Nakamura, H Idei, M Hasegawa, A Fujisawa, A Kuzmin, K Matsuoka
  • Journal Title: Physics of Plasmas Volume: 23 Pages: 082507
  • DOI: http://dx.doi.org/10.1063/1.4960117
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Comparative studies of inner and outer divertor discharges and a fueling study in QUEST (2016)
  • Author(s): O Mitarai, K Nakamura, M Hasegawa, T Onchi, H Idei, A Fujisawa, K Hanada, H Zushi, A Higashijima, H Nakashima, S Kawasaki, K Matsuoka, S Koike, T Takahashi, H Tsutsui
  • Journal Title: Fusion Engineering and Design Volume: 109-111 Pages: 1365-1370
  • DOI: http://doi.org/10.1016/j.fusengdes.2015.12.022
  • Peer Reviewed
• [Journal Article] Response of the far scrape-off layer plasma to strong gas puffing in the high poloidal beta configuration of the QUEST spherical tokamak (2016)
  • Author(s): T Onchi, H Zushi, K Mishra, Y Oyama, Y Nagashima, K Hanada, H Idei, M Hasegawa, A Kuzmin, H Miura, K Nakamura, A Fujisawa, K Nagaoka
  • Journal Title: Plasma Physics and Controlled Fusion Volume: 58 Pages: 115004
  • DOI: https://doi.org/10.1088/0741-3335/58/11/115004
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Presentation] Non-inductive current built-up by local electron cyclotron heating and current drive with a 28 GHz focused beam on QUEST (2016)
  • Author(s): Takumi Onchi
  • Organizer: APS Division of Plasma Physics Meeting 2016, abstract #PP10.025
  • Place of Presentation: San Jose, California, United States of America
  • Year and Date: 2016-10-31 – 2016-11-04
  • Int'l Joint Research