Recipe of Helium Neutral Beam Injection for Studying Helium Transport in LHD

IF 2.3 4区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Journal of Fusion Energy Pub Date : 2025-12-09 DOI:10.1007/s10894-025-00539-7

Yutaka Fujiwara, Kenichi Nagaoka, Gen Motojima, Hiroyuki Yamaguchi, Mamoru Sato, Naoyuki Suzuki, Hiromi Kato, Ryuichi Sakamoto, Daisuke Nagata, Shuji Kamio, Masaki Osakabe, Katsuyoshi Tsumori, Haruhisa Nakano, Mikiro Yoshinuma, Tatsuya Kobayashi, Katsumi Ida

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Abstract

To advance the understanding of helium transport physics, helium neutral beam (He-NB) experiments were initiated in the Large Helical Device (LHD) during the FY2021 experimental campaign. To facilitate these investigations, modifications were implemented in both the impurity exhaust system and the neutral beam (NB) injection system, enabling the use of the helium beam in a typical fusion experimental environment. In the positive-ion-source-based NB system—originally designed for hydrogen and deuterium beams—the gas supply lines were adapted to introduce helium and argon into the ion sources, while argon was injected into the neutralizer cells. These modifications allowed for the injection of a high current and high focused 78 keV He-NB into the plasma. To improve helium exhaust efficiency at main vessel, turbo-molecular pumps were installed, increasing the effective pumping speed by approximately 1.4 times. During He-NB operation, a gradual decrease in the arc current of the NB ion source was observed with each discharge. This effect was attributed to the formation of helium bubbles on the tungsten filament surface, and a recovery method using argon gas discharges was successfully demonstrated. Plasma heating by He-NB injection was confirmed, and both energetic helium ions and bulk helium ions were successfully measured. Their spatial distributions were also observed. These results contribute to a deeper understanding of helium behavior in fusion plasma and offer valuable insights for future helium transport studies.

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用于LHD中氦输运研究的氦中性束注入配方

为了促进对氦输运物理的理解，在2021财年的实验活动期间，在大型螺旋装置（LHD）上启动了氦中性束（He-NB）实验。为了促进这些研究，对杂质排气系统和中性束（NB）注入系统进行了修改，使氦束能够在典型的聚变实验环境中使用。在基于正离子源的NB系统中，最初是为氢和氘光束设计的，气体供应线用于将氦气和氩气引入离子源，同时将氩气注入中和剂细胞。这些改进允许在等离子体中注入高电流和高聚焦的78 keV He-NB。为了提高主容器的氦排气效率，安装了涡轮分子泵，将有效抽气速度提高了约1.4倍。在He-NB工作过程中，随着每次放电，NB离子源的弧电流逐渐减小。此效应归因于在钨丝表面形成氦气泡，并成功地演示了利用氩气放电回收的方法。证实了氦- nb注入对等离子体的加热作用，并成功地测量了高能氦离子和体积氦离子。并观察了它们的空间分布。这些结果有助于更深入地了解氦在聚变等离子体中的行为，并为未来氦输运研究提供有价值的见解。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Fusion Energy 工程技术-核科学技术

CiteScore

2.20

自引率

0.00%

发文量

审稿时长

2.3 months

期刊介绍： The Journal of Fusion Energy features original research contributions and review papers examining and the development and enhancing the knowledge base of thermonuclear fusion as a potential power source. It is designed to serve as a journal of record for the publication of original research results in fundamental and applied physics, applied science and technological development. The journal publishes qualified papers based on peer reviews. This journal also provides a forum for discussing broader policies and strategies that have played, and will continue to play, a crucial role in fusion programs. In keeping with this theme, readers will find articles covering an array of important matters concerning strategy and program direction.