| 研究課題/領域番号 |
16K18341
|
|---|
| 研究機関 | 国立研究開発法人量子科学技術研究開発機構 |
|---|
研究代表者 |
Bierwage Andreas 国立研究開発法人量子科学技術研究開発機構, 六ヶ所核融合研究所 核融合炉システム研究開発部, 主幹研究員(定常) (10584691)
|
|---|
| 研究期間 (年度) |
2016-04-01 – 2020-03-31
|
| キーワード | Abrupt large events / Anomalous self-heating / Energetic particles / Hybrid simulation / Gyrokinetic simulation / Tokamak plasma |
|---|
| 研究実績の概要 |
1) Reproducibility tests of simulations of Abrupt Large relaxation Event (ALE) in a JT-60U tokamak plasma were performed using the MHD-PIC hybrid code MEGA. Our previous results were confirmed in these tests, so a paper summarizing our work on ALEs was submitted to Nature Communications. A paper describing the methods used was published in Computer Physics Communications.
2) The results of our feasibility study of the Alfven acoustic self-heating channels performed with the linear gyrokinetic code LIGKA were published in Nuclear Fusion. Meanwhile, the PI visited IPP Garching/Germany, were he learned and tested a new version of LIGKA implemented there by Dr. Lauber. The new version includes effects of magnetic drifts and higher-order Larmor-radius corrections, which are necessary to better quantify the strength of resonant drive by fast ions and radiative damping of kinetic Alfven waves. The verification of the extended code is still in progress.
3) The data acquired in MEGA simulations were carefully analyzed using Poincare plots. These analyses were performed for a variety of cases for JT-60U and JT-60SA tokamaks, with and without MHD instabilities, beta-induced Alfven continuum modes (BACM), ALEs and other fast-ion-driven instabilities. While analyses are still ongoing, we have recently discovered that magnetic reconnection can occur when fast-ion driven instabilities grow to large amplitudes (e.g. during ALE). Potentially important effect on the background plasma and mode dynamics are under investigation. This work was selected as an invited talk for 2018 EPS Conference.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
* Several research and development goals originally set for FY2017 and FY2018 were already achieved in FY2016. Thus, in FY2017 we focused on the dissemination of the results, which also required careful reproducibility tests.
* Extensions to the LIGKA model as required for the gyrokinetic simulations planned for FY2019 were implemented and the verification of the model and code has been started.
* The study of low-frequency modes (originally planned for FY2016) was postponed once more. One reason is that we did not have an in-house dedicated supercomputer system. Another reason is that we decided to dedicate more time to new effects that we have recently discovered, since we anticipate a bigger impact.
|
| 今後の研究の推進方策 |
* Our discovery of magnetic reconnection induced by fast-ion-driven modes was chosen as a new high-priority item for this project due its potentially strong effect on both the bulk plasma and fast ion dynamics. For instance, the changes in magnetic topology may turn out to be an important factor in the ALE trigger mechanism that we are trying to unravel.
* Another reason for investigating magnetic island effects is their possible role for Alfven-acoustic couplings. Our recent gyrokinetic analyses using LIGKA were performed for an axisymmetric equilibrium. However, in the vicinity of magnetic islands, magnetic flux surfaces are compressed and expanded in a spatially periodic fashion, which may change the coupling strength between Alfvenic and acoustic branches. Besides being of theoretical interest, such an effect may also be used for measuring anomalous heating in experiments: even if absolute measurements turn out to be difficult, a comparison of anomalous heating with and without magnetic islands may be feasible. We plan to investigate these ideas further in the future.
* We will expand our simulations and analyses to shift our attention to high-beta JT-60SA tokamak plasma scenarios, since we hope that our numerical predictions may be validated in future JT-60SA experiments. Work in this direction has been successfully started with support from 2016 Masaji Yoshikawa Prize for Fusion Energy. This work will be continued in FY2018 using this Kakenhi, contributing to the JT-60SA research plan and to integrated modeling efforts as planned for FY2019 of this research project.
|
| 次年度使用額が生じた理由 |
* 371,080 JPY: Cover part of the publication charges (around 1,000,000 JPY) that will be due in the case that Nature Communications accepts our manuscript. In FY2017, 271,080 JPY were saved and transfered to FY2018 for this purpose.
* 400,000 JPY: Cover expenses for an international business trip to IPP Garching/Germany in summer 2018. The main purpose of this collaboration trip is to continue careful verification tests of the new version of LIGKA. This work can be performed efficiently only if the PI meets the developer Dr. Lauber for about 1-2 weeks at least once a year. At least one such meeting will be funded with this Kakenhi. If the results can be verified, we plan to write two papers: one about the new model and methods used, and one reporting the latest results.
|
