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Author Mutoh, T. ♦ Seki, T. ♦ Saito, K. ♦ Kasahara, H. ♦ Seki, R. ♦ Kamio, S. ♦ Kumazawa, R. ♦ Kubo, S. ♦ Shimozuma, T. ♦ Yoshimura, Y. ♦ Igami, H. ♦ Takahashi, H. ♦ Ii, T. ♦ Makino, R. ♦ Nagaoka, K. ♦ Nomura, G. ♦ Shinya, T.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ATOMIC AND MOLECULAR PHYSICS ♦ CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ ANTENNAS ♦ ECR HEATING ♦ ELECTRON DENSITY ♦ ELECTRON TEMPERATURE ♦ HEATING SYSTEMS ♦ HELIOTRON ♦ HELIUM ♦ HYDROGEN ♦ ICR HEATING ♦ IMPEDANCE ♦ ION CYCLOTRON-RESONANCE ♦ ION TEMPERATURE ♦ IONS ♦ KEV RANGE 01-10 ♦ LHD DEVICE ♦ PIPES ♦ PLASMA ♦ STEADY-STATE CONDITIONS ♦ TRANSFORMERS
Abstract Recent progress in an ion cyclotron range of frequencies (ICRF) heating system and experiment results in a Large Helical Device (LHD) are reported. Three kinds of ICRF antenna pairs were installed in the LHD, and the operation power regimes were extended up to 4.5 MW; also, the steady-state operation was extended for more than 45 min in LHD at a MW power level. We studied ICRF heating physics in heliotron configuration using a Hand Shake type (HAS) antenna, Field Aligned Impedance Transforming (FAIT) antenna, and Poloidal Array (PA) antenna, and established the optimum minority-ion heating scenario in an LHD. The FAIT antenna having a novel impedance transformer inside the vacuum chamber could reduce the VSWR and successfully injected a higher power to plasma. We tested the PA antennas completely removing the Faraday-shield pipes to avoid breakdown and to increase the plasma coupling. The heating performance was almost the same as other antennas; however, the heating efficiency was degraded when the gap between the antenna and plasma surface was large. Using these three kinds of antennas, ICRF heating could contribute to raising the plasma beta with the second- and third-harmonic cyclotron heating mode, and also to raising the ion temperature as discharge cleaning tools. In 2014, steady-state operation plasma with a line-averaged electron density of 1.2 × 10{sup 19} m{sup −3}, ion and electron temperature of 2 keV, and plasma sustainment time of 48 min was achieved with ICH and ECH heating power of 1.2 MW for majority helium with minority hydrogen. In 2015, the higher-power steady-state operation with a heating power of up to 3 MW was tested with higher density of 3 × 10{sup 19} m{sup −3}.
ISSN 0094243X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-12-10
Publisher Place United States
Volume Number 1689
Issue Number 1


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