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Appearance of hollow soft x-ray emissivity distribution in deep-reversal discharge in reversed field pinch

A Sanpei, H Himura, S Inagaki2026年6月Plasma Physics and Controlled FusionIF 2.2出版社

Self-generation of toroidal magnetic flux and particle acceleration during a reconnection event are two of the main characteristics of the reversed field pinch (RFP) configuration. However, direct experimental observations that explicitly identify the precise location where the effects of reconnection events are strongly manifested in deep-reversal discharges are lacking. This paper presents the first experimental observation of a distinct hollow soft x-ray (SXR) emissivity distribution in the deep-reversal discharge () of the low-aspect-ratio (low-) RFP device RFP of low-aspect-ratio experiment. Using a high-speed SXR imaging system, we successfully captured the rapid dynamics of the internal plasma structure during an oscillation event. Detailed profile analysis and equilibrium reconstruction estimations confirm that the observed hollow SXR emission is confirmed to be highly localized in the vicinity of the resonant surface, which is the reversal surface (at a normalized radius of ). The SXR intensity synchronizes with the plasma current oscillation, peaking approximately in synchronization with the onset of the rapid drop phase of the oscillation cycle. Analysis of the magnetohydrodynamic (MHD) mode activity suggests that the generation of this hollow emissivity structure is associated with particle acceleration resulting from magnetic reconnection, which is associated with the dynamo effect. While the potential contribution of impurity radiation cannot be entirely excluded based on visible light spectroscopy, the synchronization with magnetic fluctuations indicates that the dynamo effect plays a primary role. The findings of this study provide valuable insights into the nonlinear MHD dynamics in RFP plasmas and the formation of a localized poloidal current sheet.

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Reversed field pinchSoft x-ray

AIによる論文要約

反場ピンチ装置における深反転放電での軟X線放射率分布の中空構造の出現
JA核融合プラズマ物理学の研究者、特に反場ピンチや磁気リコネクション、ダイナモ現象に興味がある学生や専門家#反場ピンチ #RFP #軟X線 #磁気リコネクション #ダイナモ効果
LLM向け: {"Title": "深反転放電における中空軟X線放射分布の観測", "Authors": "不明(論文から取得不可)", "Research Objectiv…

反場ピンチ(RFP)装置では、磁気リコネクションによるダイナモ効果が重要ですが、深反転放電でその効果が顕著な場所は不明でした。本研究は、低アスペクト比RFP装置RELAXにおいて、高速軟X線イメージングシステムを用いて、プラズマ内部構造の急速な変化を初めて観測しました。発振イベント中に、反転面(規格化半径0.6付近)に局在した中空状の軟X線放射分布を確認しました。この放射強度はプラズマ電流と同期し、急減位相の開始時にピークに達します。MHDモード解析から、磁気リコネクションに伴う粒子加速が原因であることが示唆されました。不純物放射の可能性は完全には排除できませんが、磁気揺動との同期からダイナモ効果が主因と考えられます。この発見は、RFPプラズマの非線形MHD力学と局所的なポロイダル電流シート形成の理解に重要です。

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