2021 Fiscal Year Final Research Report

Observation of self-organized FRC formation in a collisional-merging experiment

Research Project

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Project/Area Number	19K21868
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 14:Plasma science and related fields
Research Institution	Nihon University
Principal Investigator	ASAI Tomohiko 日本大学, 理工学部, 教授 (00386004)
Co-Investigator(Kenkyū-buntansha)	長山好夫日本大学, 核融合科学研究所, 名誉教授 (10126138) 高橋俊樹群馬大学, 大学院理工学府, 准教授 (10302457) 比村治彦京都工芸繊維大学, 電気電子工学系, 教授 (30311632) 高橋努日本大学, 理工学部, 教授 (50179496) 水口直紀核融合科学研究所, ヘリカル研究部, 准教授 (70332187)
Project Period (FY)	2019-06-28 – 2022-03-31
Keywords	磁場閉じ込めプラズマ / 自己組織化
Outline of Final Research Achievements	Self-organized field-reversed configuration-like (FRC) formation was observed after the super-sonic/Alfvenic collisional merging of two FRCs. In this experiment, two FRCs were generated initially in two separate field-reversed theta-pinch (FRTP) type formation regions. Those two formation regions are coaxially connected to opposite ends of a cylindrical confinement chamber. The formed FRCs are oppositely-translated and collide in the middle of the confinement chamber at super- sonic/Alfvenic velocity. During the collision, the merged plasmoid experiences destructive disturbance and loses its fast toroidal flow and characteristic FRC property of having a field-reversed magnetic configuration to become a magnetized plasma without ordered structure. After this dynamic collision, a magnetic configuration of FRC with fast toroidal rotation is self-organized within a few tens of microseconds. This observation indicates robustness of the extremly high-beta, simple magnetic configuration.
Free Research Field	核融合学，プラズマ物理学
Academic Significance and Societal Importance of the Research Achievements	小型で効率が高い核融合炉心や中性子排出のない先進燃料核融合の実現には，高ベータ化が必須であり，これを極限まで突き詰めると，プラズマ電流と閉じ込め磁場が完全に直交し，トーラス中心に穴が開いていないFRCとなる。その特異な磁場配位のため，局所βはその大部分で１を超え，したがってイオンは磁化していないなど，多くの点で他の磁場配位と異なる性質を示し，同時にその緩和のメカニズムには未解明な点も多い。本研究成果は，このFRCの堅固な安定性を示す結果であり，米国の民間企業などでも開発が開始されたFRCによる超高ベータ核融合炉心の実現に貢献する結果である。