Plasma and Fusion Research
Volume 10, 1402001 (2015)
Regular Articles
- 1)
- National Institute for Fusion Science, Toki 509-5292, Japan
- 2)
- The Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
- 3)
- Department of Nuclear Engineering, Kyoto University, Kyoto 615-8530, Japan
- 4)
- Department of Mechanical Engineering and Science, Kyoto University, Kyoto 615-8540, Japan
Abstract
High-ion temperature experiments in the Large Helical Device (LHD) are categorized in terms of the heating scenarios that are closely related to the development of neutral beam injection (NBI) systems. Although high-energy tangential negative-NBI heating has greatly contributed to extending the plasma parameter regime in LHD, the ion temperature does not increase because the electron heating is dominant with negative-NBIs. In the high-Z discharges, it was demonstrated that the ion temperature increased with an increasing ion heating power and achieved 13.5 keV with the negative-NBIs. Low-energy perpendicular positive-NBIs were installed for the ion heating, and the ion temperature was increased to more than 7 keV in hydrogen discharges. In the high-ion temperature plasmas, an ion internal transport barrier (ion ITB) was formed, and the impurity hole was observed in the core. Long-pulse ion cyclotron range of frequency heating (ICH)/electron cyclotron resonance heating (ECRH) helium discharges are effective for wall conditioning, leading to a decrease in the neutral density and a peaked density profile. Consequently, the ion heating efficiency increases in the core, and the central Ti is raised up to 7.5 keV. With the superposition of high-power ECRH, high-performance plasmas of Ti ∼ Te ∼ 6 keV were obtained. In the planned deuterium experiment, the ion heating power will be increased with the deuterium beam injection, and Ti = 10 keV is expected.
Keywords
high-ion temperature plasma, Large Helical Device, NBI heating, high-Z discharge, ion ITB, impurity hole, long-pulse discharge cleaning, deuterium experiment, ion and electron root
Full Text
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This paper may be cited as follows:
Yasuhiko TAKEIRI, Osamu KANEKO, Masaki OSAKABE, Kenichi NAGAOKA, Sadayoshi MURAKAMI, Hiromi TAKAHASHI, Haruhisa NAKANO, Katsumi IDA, Shigeru MORITA, Masayuki YOKOYAMA, Mikiro YOSHINUMA, Keisuke FUJII, Motoshi GOTO, Chihiro SUZUKI, Ryosuke SEKI, Katsuyoshi TSUMORI, Katsunori IKEDA, Masashi KISAKI, Takashi MUTOH, Hiroshi YAMADA, Akio KOMORI and the LHD Experiment Group, Plasma Fusion Res. 10, 1402001 (2015).