2018 Fiscal Year Research-status Report
Simulation study of the energy channel and the particle radial transport due to the energetic particle driven geodesic acoustic mode
| Project/Area Number |
18K13529
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| Research Institution | National Institute for Fusion Science |
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Principal Investigator |
Wang Hao 核融合科学研究所, ヘリカル研究部, 助教 (30724760)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Keywords | EGAM Channeling / MEGA simulation / EGAMs in LHD / energy transfer / geodesic acoustic mode / energetic particles / resonant particles / sideband resonance |
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| Outline of Annual Research Achievements |
The progress is made very smoothly. Energetic particle driven geodesic acoustic modes (EGAMs) in LHD plasmas are investigated using MEGA code. The EGAM channeling is reproduced by simulation with realistic parameters for the first time. It is found that the sideband resonance is dominant during the energy transfer from EGAM to the bulk ions, and the transit frequencies of resonant bulk ions are one-half of the EGAM frequency. The resonance condition between EGAM and bulk ions during the establishment of EGAM channeling is quantitatively revealed. Lower mode frequency makes higher energy transfer efficiency, because there is stronger interaction between lower frequency mode and bulk ions.
In the future, further investigation of EGAM will be made. First, HINT code will be learned by the applicant. Then, the applicant will be able to generate the related equilibrium files by himself. Second, the applicant will investigate the interaction between EGAM and another unidentified mode which was observed in LHD. The applicant is planning to reproduce this phenomena, to identify the chirping mode, and clarify the mechanism of the interaction between these 2 modes. Third, the applicant will investigate the experimental condition of EGAM channeling in ASDEX-Upgrade.
One manuscript was submitted to Nuclear Fusion and very positive comments from referees were received. Another manuscript was completed and now is being polished carefully, and it will be submitted to Physics of Plasma soon. Also, many presentations were made in both domestic and international conferences.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Energetic particle driven geodesic acoustic modes (EGAMs) in the Large Helical Device (LHD) plasmas are investigated using MEGA code. MEGA is a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic (MHD) fluid and in the present work, both the energetic particles and bulk ions are described by the kinetic equations.
The low frequency EGAMs are reproduced. Also, the energy transfer is analyzed and the bulk ion heating during the EGAM activity is observed. The ions obtain energy when the energetic particles lose energy, and this indicates that an energy channel is established by EGAM. The EGAM channeling is reproduced by simulation with realistic parameters for the first time. The heating power to bulk ions is 3.4 kilo-watt per cubic meter.
It is found that the sideband resonance is dominant during the energy transfer from EGAM to the bulk ions, and the transit frequencies of resonant bulk ions are one-half of the EGAM frequency. The resonance condition between EGAM and bulk ions during the establishment of EGAM channeling is quantitatively revealed.
The energy transfer efficiency of the EGAM channeling is investigated under various conditions. Lower mode frequency makes higher energy transfer efficiency, because there is stronger interaction between lower frequency mode and bulk ions.
In addition, both the low-frequency and high-frequency branches of EGAMs are investigated. The transition between low-frequency and high- frequency branches of EGAM is decided by the slope of energetic particle velocity distribution.
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| Strategy for Future Research Activity |
Further investigation of EGAM will be made by 3 steps.
First, HINT code will be learned by the applicant and be well used for MEGA simulation. The realistic 3-dimensional equilibrium in LHD is important for MEGA simulation. Until now, all the HINT equilibrium files are generated by the HINT developer, not by the applicant himself. Now, the applicant is learning HINT code. Then, in the future, in order to investigate various phenomena, the applicant will be able to generate the related equilibrium files by himself, and this will make the research more flexible and more rapidly.
Second, the applicant will investigate the interaction between EGAM and another mode. Recently, the interaction between a chirping EGAM and an unidentified chirping energetic particle driven mode was observed in LHD experiment. The chirping EGAM appears after the unidentified chirping mode, and thus the EGAM was likely triggered by the unidentified mode. Also, the loss of energetic particles was observed. This interesting phenomena was reported in JPS meeting in Fukuoka. The applicant is planning to reproduce this phenomena, to identify the chirping mode, and clarify the mechanism of the interaction between these 2 modes.
Third, the applicant will investigate the experimental condition of EGAM channeling in ASDEX-Upgrade. Also, the interactions between EGAMs and TAEs in ASDEX-Upgrade will be reproduced, and the mechanism will be clarified.
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| Causes of Carryover |
According to the plan, I need to buy the Mathematica Software in the first fiscal year. However, until now, the data analysis and visualization works are not very complicated, and thus, these works can be done by Scilab Software which is free of charge. Then, I decide to buy the Mathematica Software in the second fiscal year, for the research of interactions between multi modes.
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