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17–22 Oct 2016
Kyoto International Conference Center
Japan timezone

Extension of Operational Regime in High-Temperature Plasmas and Effect of ECRH on Ion Thermal Transport in the LHD

19 Oct 2016, 17:40
20m
Kyoto International Conference Center

Kyoto International Conference Center

Takaragaike, Sakyo-ku, Kyoto 606-0001 Japan
Oral PPC - Plasma Overall Performance and Control Steady State and Hybrid scenarios

Speaker

Dr Hiromi Takahashi (National Institute for Fusion Science)

Description

In future reactors, the fusion reaction is expected to be sustained under the electron heating dominant condition, where both ion temperature and electron temperature are high. Thus the characterization of the thermal transport for the plasmas, of which ion temperature and electron temperature are simultaneously high, is necessary. In recent years, an integration of high ion temperature and high electron temperature has been successfully achieved in the LHD. In FY2014, one high power gyrotron (154 GHz, 1 MW) was newly installed, and since then 5 gyrotrons with 1-MW output power each have been under operation and the total ECRH power reached 5.4 MW. We finely adjusted the ECRH injection angle and the EC wave polarization taking account of the actual plasma profiles in real time. Simultaneous high ion temperature and high electron temperature regime was successfully extended due to the upgraded ECRH system and the optimization of the ECRH injection. Such high-temperature plasmas were realized by the simultaneous formation of an ion ITB and an electron ITB by the combination of high power NBI and ECRH. In the heating condition, a seesaw-like behavior of the ion thermal transport between core and edge has been observed. Both in the plasma core and the edge, the electron temperature and the gradient increased with increase in ECRH power. On the other hand, the ion thermal confinement was degraded in the plasma core with increase of the ratio of the electron temperature to the ion temperature by the on-axis ECRH. In contrast, the ion thermal confinement was found to be improved at the plasma edge. The ion thermal diffusivity normalized by the gyro-Bohm factor was found to be reduced by 70% at the edge. Then the spatiotemporal coherence of the electron density fluctuations at the plasma edge clearly decreased. The improvement of the ion thermal confinement at the edge led to increase in the ion temperature in the entire plasma region even though the core transport was degraded.
Country or International Organization Japan
Paper Number PPC/1-1

Primary author

Dr Hiromi Takahashi (National Institute for Fusion Science)

Co-authors

Dr Akihiro Shimizu (National Institute for Fusion Science) Dr Chihiro Suzuki (National Institute for Fusion Science) Dr Haruhisa Nakano (National Institute for Fusion Science) Dr Hayato Tsuchiya (National Institute for Fusion Science) Dr Hiroe Igami (National Institute for Fusion Science) Dr Hiroshi Kasahara (National Institute for Fusion Science) Dr Ichihiro Yamada (National Institute for Fusion Science) Prof. Katsumi Ida (National Institute for Fusion Science) Dr Katsunori Ikeda (National Institute for Fusion Science) Dr Katsuyoshi Tsumori (National Institute for Fusion Science) Dr Kenichi Nagaoka (National Institute for Fusion Science) Dr Kenji Saito (National Institute for Fusion Science) Dr Kenji Tanaka (National Institute for Fusion Science) Prof. MASAYUKI YOKOYAMA (National Institute for Fusion Science) Dr Masahiko Emoto (National Institute for Fusion Science) Prof. Masaki Osakabe (National Institute for Fusion Science) Dr Masashi Kisaki (National Institute for Fusion Science) Dr Mikirou Yoshinuma (National Institute for Fusion Science) Dr Motoki Nakata (National Institute for Fusion Science) Dr Motoshi Goto (National Institute for Fusion Science) Prof. Osamu Kaneko (National Institute for Fusion Science) Dr Ryo Yasuhara (National Institute for Fusion Science) Dr Ryohei Makino (National Institute for Fusion Science) Dr Ryosuke Seki (National Institute for Fusion Science) Dr Sadayoshi Murakami (Departement Nuclear Engineering, Kyoto University) Prof. Shigeru Morita (National Institute for Fusion Science) Prof. Shin Kubo (National Institute for Fusion Science) Dr Shuji Kamio (National Institute for Fusion Science) Dr TAKESHI IDO (National Institute for Fusion Science) Prof. Takashi Mutoh (National Institute for Fusion Science) Prof. Takashi Shimozuma (National Institute for Fusion Science) Dr Tatsuya Kobayashi (National Institute for Fusion Science) Tetsuo Seki (National Institute for Fusion Science) Dr Tetsutarou Oishi (National Institute for Fusion Science) Dr Tomohiro Morisaki (National Institute for Fusion Science) Dr Toru Tsujimura (National Institute for Fusion Science) Yasuhiko Takeiri (National Institute for Fusion Science) Dr Yasuo Yoshimura (National Institute for Fusion Science)

Presentation materials