Development of a new regime of helical confinement system by optimization of external coils

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K13904
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: National Institute for Fusion Science
• Principal Investigator: Yamaguchi Hiroyuki 核融合科学研究所, 研究部, 准教授 (90797101)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 核融合 / ヘリカル方式 / 最適化 / 遺伝的アルゴリズム / ダイバータ配位 / 自由曲線

Outline of Final Research Achievements

We developed a new method to numerically optimize the plasma confinement magnetic field of a fusion reactor by varying the external coil shape and current value, and explored coil and magnetic field configurations that can achieve both improved confinement and magnetohydrodynamic (MHD) stability, which are issues in helical-type fusion reactors, and realize a divertor configuration. By expressing and optimizing the shape of a continuous helical coil using a cubic B-spline curve, we have shown that it is possible to generate a diverter-leg-shaped magnetic field line structure in an advanced magnetic field configuration with improved neoclassical transport and MHD stability. By incorporating the magnetic field line structure outside the outermost magnetic surface into the optimization, we have constructed a helical coil that can secure blanket space while also showing good neoclassical confinement and providing MHD stability.

Free Research Field

核融合学、プラズマ物理

Academic Significance and Societal Importance of the Research Achievements

従来、核融合炉の設計は少数のコイル形状パラメータの調整あるいは磁気面フーリエモードの数値最適化によって行われていた。本研究ではコイル形状を最適化の直接の変量とすることで、これまでの核融合炉設計手法では不可能であった、工学特性と物理特性の同時最適化を世界で初めて可能とした。また、遺伝的アルゴリズムを応用した核融合炉設計の有効性を示した。その成果として得られた新たなコイル形状は、将来の核融合炉で必須となる高性能プラズマの閉じ込め、熱・粒子制御、燃料生産の同時達成という挑戦に向けた新たな経路を開くものである。