Intermittent plasma bursts across the last closed flux surface in a highly overdense spherical torus generated by electron Bernstein wave heating

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01198
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: Kyoto University
• Principal Investigator: Uchida Masaki 京都大学, エネルギー科学研究科, 准教授 (90322164)
• Co-Investigator(Kenkyū-buntansha): 田中 仁 京都大学, エネルギー科学研究科, 教授 (90183863)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 球状トーラス / 無誘導起ち上げ / 電子バーンスタイン波 / 不安定性

Outline of Final Research Achievements

A soft X-ray computer tomography system and a magnetic probe array system were designed, fabricated, and installed in the LATE device to observe the plasma behavior during the intermittent plasma bursts across the last closed flux surface (LFCS) in highly overdense spherical tokamak plasmas maintained solely by the electron Bernstein wave heating and current drive. Intense and frequent plasma bursts are observed when the plasma current reaches 10kA and the electron density exceeds 7 times the plasma cutoff density. The X-ray reconstruction image shows a peaked profile centered at the plasma current center which is located the outboard side of the LCFS. Magnetic probe array data shows the toroidal current variation such that the ejected electrons (or ions) from inside the LCFS upon the burst move from the midplane to the top (or bottom) of the device along the magnetic field lines.

Free Research Field

プラズマ理工学

Academic Significance and Societal Importance of the Research Achievements

電子バーンスタイン波により無誘導に形成された遮断密度の約７倍の球状トカマクにおいて、電子密度上昇とともに現れる間欠的プラズマ噴出の詳細課程について、軟X線CTシステムの設計・製作、磁気プローブ増設、重イオンビームプローブの整備を行い、プラズマ噴出の際のトロイダル電流の変化、軟X線発光像の変化を追跡した。この結果をもとにプラズマ噴出の制御が可能となれば、球状トカマクの無誘導起動の実現性が高まり、低コスト核融合炉へ道が開ける。